<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">One other possibility is to provide a separate path for "comm_world" access - something like the MPI_WIN_WORLD in ticket #139 . <div><br></div><div>I've also added a note to the page to remind readers that requiring a feature does prohibit supporting a specialization.</div><div><br></div><div>Bill</div><div><br><div><div>On Sep 4, 2009, at 11:11 AM, Underwood, Keith D wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div lang="EN-US" link="blue" vlink="purple"><div class="Section1"><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I agree that the issue is fundamental on some networks, but it is not going to be fundamental across all networks. I’m more worried about the “not broken” networks ;-) Actually, I’m more worried about the ability to build a not-broken network for the purpose. And, having a collective allocation fixes most of the issues, but it does leave some open questions. I would like us to update the design goal to acknowledge that collective allocation is allowed, but not required.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Anyway, as far as what I’m worried about, I’ll use a very specialized example to make the point...<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">So, I’ll start by assuming shmem, Portals 3.3, a lightweight kernel, and hardware optimized to try to do that. I apologize to those not versed in Portals ;-)<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Let’s say that you shmem uses Portals to expose the entire virtual address space with an ME. The ME is persistent (never changes) and is the only item on a given portal table entry. The hardware takes the head of that list and caches it in an associative matching structure. Now you can process a message from the network every cycle… Oh, the hardware has to do virtual to physical address translation and it had better do protection based on whether a virtual page is physically backed or not, but, wait, I can constrain the kernel to always guarantee that ;-)<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">At the transmitter, let’s say that you can push a (PE, portal table entry, offset) tuple as the target address directly to the hardware somehow… the T3E did something like this using E-registers, a centrifuge, and a machine partitioning approach. Ok, that takes a change to the Portals API, but we did that for Portals 4. Now you can push messages into the network very quickly too (PE is in the shmem call, portal table entry is a constant, offset is in virtual address space and is symmetric across nodes, so it is one or two arithmetic instructions).<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">And, of course, there are platforms like the Cray X1 that had even better hardware support for this type of operation.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Ok, so, how does the proposal we are discussing for MPI differ?<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0.5in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; text-indent: -0.25in; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><span>1)<span style="font: normal normal normal 7pt/normal 'Times New Roman'; "> <span class="Apple-converted-space"> </span></span></span></span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">There is a communicator context. How much work this is depends on how much you need from that context.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0.5in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; text-indent: -0.25in; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><span>2)<span style="font: normal normal normal 7pt/normal 'Times New Roman'; "> <span class="Apple-converted-space"> </span></span></span></span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">There is a “memory object”. How many of these are there? Is there anything that strongly encourages the user to keep it relatively small? If not, how do I build good hardware support? I can’t have an unlimited number of unique system wide identifiers.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0.5in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; text-indent: -0.25in; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><span>3)<span style="font: normal normal normal 7pt/normal 'Times New Roman'; "> <span class="Apple-converted-space"> </span></span></span></span><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">We have the nagging issue of non-coherent architectures and heterogeneous architectures. Ok, that one is probably workable, since vendor specific MPI implementations may drop both if their architecture is coherent and homogeneous. Of course, if it causes us to do something weird with the completion semantics (ala the ability to defer all actual data transfer to the end of a window in the current MPI-2 one sided operations), that could be an issue.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">So, the telling issue will be: if you put this proposal on a Cray X1 (ORNL still have one of those running?), how does it compare to the message rate of shmem on the same platform? Perhaps doing such a prototype would help us advance the discussion more than anything. We would have a baseline where we could say “what would it take to get competitive?”. Unfortunately, I don’t know of many other places that currently support shmem well enough to make a good comparison.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Keith<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="border-top-style: none; border-right-style: none; border-bottom-style: none; border-width: initial; border-color: initial; border-left-style: solid; border-left-color: blue; border-left-width: 1.5pt; padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 4pt; "><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span><a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma-bounces@lists.mpi-forum.org</a><span class="Apple-converted-space"> </span>[<a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mailto:mpi3-rma-bounces@lists.mpi-forum.org</a>]<span class="Apple-converted-space"> </span><b>On Behalf Of<span class="Apple-converted-space"> </span></b>Vinod tipparaju<br><b>Sent:</b><span class="Apple-converted-space"> </span>Friday, September 04, 2009 9:41 AM<br><b>To:</b><span class="Apple-converted-space"> </span>MPI 3.0 Remote Memory Access working group<br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Mpi3-rma] MPI3 RMA Design Goals<o:p></o:p></span></div></div></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><o:p> </o:p></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span lang="EN" style="font-size: 10pt; font-family: Verdana, sans-serif; ">hence the word "similar" to MDBind. MDBind can potentially a lot more as far as preparing the network. Binding is for reducing latency, for no other reason. I agree that in your example of random target communication, it is not useful.<br> <br>You are right and I have always agreed that when you do need such a table of mem-object data structures or a table of pointers under the hood of the implementation of collective mem-object data structures, random accesses will incur cache misses and latency. I get that. My points are(please let me know if you disagree to any of the bullets):<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0.5in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span lang="EN" style="font-size: 10pt; font-family: Verdana, sans-serif; ">1) the problem doesn't exist if collective memobjs are used and the memobjs can internally allocate symmetric memory (same pointers and same "keys" across the system).<br>2) This is a more fundamental problem associated with if it is possible to allocate symmetric memory and corresponding symmetric key-ids on networks that require them.<span class="Apple-converted-space"> </span><br>3) this problem is same to shmem and these interfaces.<span class="Apple-converted-space"> </span><br>4) this problem of cache misses for random target communication call will occur if: a)the implementation of a collective object requires an array of keys or memory region identifies for sake of communication and creation of a single key is not possible, b) an array of pointers is required on this system instead of 1 symmetric pointer, and, c) if, say, ofed will have different keys on each node and the user cannot pass a number that he/she wants to be the key value -- there is nothing, you, me or any interface (the "users") can do to fix this.<o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span lang="EN" style="font-size: 10pt; font-family: Verdana, sans-serif; ">To me it seems like we are discussing about a case that is a fundamental problem that we don’t have control over. I cannot see how you would define an interface that will not have cache misses for random target communication in case of 4).<br> <br><br>So the question is are these interfaces causing cache misses when they can be avoided otherwise? I don’t think so. Do you? If you agree, we have concluded the discussion.<br></span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <br>--<br>Vinod Tipparaju ^<span class="Apple-converted-space"> </span><a href="http://ft.ornl.gov/~vinod" style="color: blue; text-decoration: underline; ">http://ft.ornl.gov/~vinod</a><span class="Apple-converted-space"> </span>^ 1-865-241-1802<br><br><br> <o:p></o:p></span></div><div class="MsoNormal" align="center" style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; text-align: center; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><hr size="2" width="100%" align="center" id="stopSpelling"></span></div><p class="MsoNormal" style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 12pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; ">From:<span class="Apple-converted-space"> </span><a href="mailto:keith.d.underwood@intel.com" style="color: blue; text-decoration: underline; ">keith.d.underwood@intel.com</a><br>To:<span class="Apple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>Date: Fri, 4 Sep 2009 08:51:12 -0600<br>Subject: Re: [Mpi3-rma] MPI3 RMA Design Goals<o:p></o:p></span></p><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Bill’s proposal was for a persistent handle for transmit operations that included things like target rank. I think there is some merit in that, though we need to evaluate the trade-offs. Unfortunately, that does not really do anything for the random communication scenario. In the non-random communication scenarios, I’m a lot less worried about things like random lookups of local data structures getting in the way. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><br>Bill’s proposal was nothing like MDBind in Portals, and MDBind does nothing to help the issue I was concerned about. Specifically, MDBind only associates local options and a local memory region with a handle. It says nothing about the target node or the target memory region. It is the lookup of information associated with the target node and target memory region that I am worried about and that is addressed by Bill’s proposal for the non-random access case.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Keith</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div><div style="border-top-style: none; border-right-style: none; border-bottom-style: none; border-width: initial; border-color: initial; border-left-style: solid; border-left-color: blue; border-left-width: 1.5pt; padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 4pt; "><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span><a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma-bounces@lists.mpi-forum.org</a><span class="Apple-converted-space"> </span>[<a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mailto:mpi3-rma-bounces@lists.mpi-forum.org</a>]<span class="Apple-converted-space"> </span><b>On Behalf Of<span class="Apple-converted-space"> </span></b>Vinod tipparaju<br><b>Sent:</b><span class="Apple-converted-space"> </span>Thursday, September 03, 2009 10:39 PM<br><b>To:</b><span class="Apple-converted-space"> </span>MPI 3.0 Remote Memory Access working group<br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Mpi3-rma] MPI3 RMA Design Goals</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div><p class="MsoNormal" style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 12pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; ">I forgot to include an important parameter (communicator) in the psuedo interface below:<br><span class="ececapple-style-span"><span style="color: black; ">Create_memobj_collective(IN user_ptr, IN size, IN communicator, OUT mem_obj)</span></span><span style="color: black; "><br><br><span class="ececapple-style-span">In addition to this Bill suggested Bind interface (something similar to MDBind in portals) that would help reduce latency for commonly re-used RMAs.</span><br><br><br></span>Vinod Tipparaju ^<span class="Apple-converted-space"> </span><a href="http://ft.ornl.gov/~vinod" style="color: blue; text-decoration: underline; ">http://ft.ornl.gov/~vinod</a><span class="Apple-converted-space"> </span>^ 1-865-241-1802<br><br><o:p></o:p></span></p><div class="MsoNormal" align="center" style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; text-align: center; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><hr size="2" width="100%" align="center"></span></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; ">From:<span class="Apple-converted-space"> </span><a href="mailto:wgropp@illinois.edu" style="color: blue; text-decoration: underline; ">wgropp@illinois.edu</a><br>To:<span class="Apple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>Date: Thu, 3 Sep 2009 13:20:38 -0500<br>Subject: Re: [Mpi3-rma] MPI3 RMA Design Goals<br><br>Design goal one allows collective creation of objects; its there because many important algorithms don't have collective (over MPI_COMM_WORLD) allocation semantics, and a design that *requires* collective creation of memory objects will also limit the use of the interface.<o:p></o:p></span></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; ">Bill<o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; ">On Sep 3, 2009, at 10:49 AM, Underwood, Keith D wrote:<o:p></o:p></span></div></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt; "><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div><div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">My commentary was on the design goals… if we<span class="ececapple-converted-space"> </span><b><i>allow</i></b><span class="ececapple-converted-space"> </span>collective creation of memory objects, and design goal #1 simply says we don’t<span class="ececapple-converted-space"> </span><b><i>require</i></b><span class="ececapple-converted-space"> </span>it, that may be ok. Design goal #1 could be interpreted to mean that you wouldn’t have collective creation in the semantic at all. Do you really anticipate one data type for an object that is either collectively or non-collectively created? </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I strongly disagree with your assertion that you can communicate with no cache misses for the non-collectively allocated memory object. In a non-collectively allocated case, you will have to keep an array of these on every process, right? i.e. one for every process you are communicating with? Randomly indexing that array is going to pound on your cache.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">We need to make sure that we don’t ignore the overhead having multiple communicators and heterogeneity. Yes, I think there are ways around this, but we should at least consider what is practical and likely rather than just what is possible.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Keith</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div style="border-top-style: none; border-right-style: none; border-bottom-style: none; border-width: initial; border-color: initial; border-left-style: solid; border-left-color: blue; border-left-width: 1.5pt; padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 4pt; "><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; ">From:</span></b><span class="ececapple-converted-space"><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; "> </span></span><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; "><a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma-bounces@lists.mpi-forum.org</a><span class="ececapple-converted-space"> </span>[<a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mailto:mpi3-rma-bounces@lists.mpi-forum.org</a>]<span class="ececapple-converted-space"> </span><b>On Behalf Of<span class="ececapple-converted-space"> </span></b>Vinod tipparaju<br><b>Sent:</b><span class="ececapple-converted-space"> </span>Tuesday, September 01, 2009 10:15 AM<br><b>To:</b><span class="ececapple-converted-space"> </span>MPI 3.0 Remote Memory Access working group<br><b>Subject:</b><span class="ececapple-converted-space"> </span>Re: [Mpi3-rma] MPI3 RMA Design Goals</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">You are correct in trying to look at the best possible case and estimating cache-misses/performance-bottlenecks. However, personally don't see any difference between this and shmem. When you cannot really allocate symmetric memory underneath, the amount of bookkeeping is same in both cases. When there is no heterogeneity, the check for this can be disabled at MPI startup. When there is heterogeneity we cannot compare with shmem.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">I cannot imagine not having symmetric/collective memory object creation to support these RMA interfaces, I think it is a must-have. Sorry I have only been saying we should have these interfaces but haven't given any example for this yet. Given how many times this same issue is coming up, I will do it now.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Consider the creation interfaces:</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Create_memobj(IN user_ptr, IN size, OUT mem_obj)</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Create_memobj_collective(user_ptr, size, OUT mem_obj)</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Assign_memobj(IN/OUT mem_obj, IN user_address, IN size) </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">There will be more details on how a mem object which is a result of create_memobj on process A will be exchanged with process B. When it is exchanged explicitly, the heterogeneity information can be created at process B. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Now take the example with symmetric object:</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Process A </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">myptr = allocate(mysize);</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Create_memobj_collective(myptr,mysize, all_obj);</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Do all kinds of RMA_Xfers</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">and an example without symmetric object:</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">myptr = allocate(mysize);</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Create_memobj(myptr,mysize,my_obj);</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> ----exchange objects here----</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">do all kinds of RAM_Xfers</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">In both cases, I can see being able to communicate without any cache misses for mem_obj.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><p class="MsoNormal" style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 12pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "><br>Vinod Tipparaju ^<span class="ececapple-converted-space"> </span><a href="http://ft.ornl.gov/~vinod" style="color: blue; text-decoration: underline; ">http://ft.ornl.gov/~vinod</a><span class="ececapple-converted-space"> </span>^ 1-865-241-1802</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></p><div class="MsoNormal" align="center" style="margin-top: 0in; margin-right: 0in; margin-bottom: 0.0001pt; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; text-align: center; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "><hr size="2" width="100%" align="center"></span></div><p class="MsoNormal" style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 12pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">From:<span class="ececapple-converted-space"> </span><a href="mailto:keith.d.underwood@intel.com" style="color: blue; text-decoration: underline; ">keith.d.underwood@intel.com</a><br>To:<span class="ececapple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>Date: Tue, 1 Sep 2009 09:07:41 -0600<br>Subject: Re: [Mpi3-rma] MPI3 RMA Design Goals</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></p><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">If we take the SINGLE_RMA_INTERFACE_DRAFT_PROPOSAL as an example, and combine it with the draft design goal #1:<span class="ececapple-converted-space"> </span></span><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">In order to support RMA to arbitrary locations, no constraints on memory, such as symmetric allocation or collective window creation, can be required</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">We get an interesting view on how difficult it can be to get “close to the metal”. So, for MPI_RMA_xfer, we have to assume that the user has some array of target_mem data items. That means the sequence of steps in user space is:</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">target_mem = ranks[dest];</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">MPI_RMA_xfer(… target_mem, dest…);</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">If we assume that the message sizes are small and the destinations randomly selected and the machine is large… every access to ranks is a cache miss, and we cannot prevent that by providing fancy hardware. This actually leads me to believe that we may need to reconsider design goal #1, or at least clarify what it means in a way that makes the access more efficient.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">MPI_RMA_xfer itself is no picnic either. If we take the draft design goal #5: The RMA model must support non-cache-coherent and heterogeneous environments, then MPI is required to maintain a data structure for every rank (ok, it has to do this anyway, but we are trying to get close to the metal) and do a lookup into that data structure with every MPI_RMA_xfer to find out if the target is heterogeneous relative to the target rank – another cache miss. Now, nominally, since this is inside MPI, a lower layer could absorb that check… or, a given MPI could refuse to support heterogeneity or… but, you get the idea. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">So, we’ve got two cache line loads for every transfer. One in the application and one in the MPI library. One is impossible to move to the hardware and the other is simply very difficult to move. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">For a contrast, look at SHMEM. Assume homogeneous, only one communicator context, and hardware mapping of ranks to physical locations. A shmem_put() of a short item could literally be turned into a few instructions and a processor store (on machines that supported such things). Personally, I think we will have done well if we can get to the point that a reasonable hardware implementation can get MPI RMA to within 2x of a reasonable SHMEM implementation. I think we have a long way to go to get there.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Keith</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div style="border-top-style: none; border-right-style: none; border-bottom-style: none; border-width: initial; border-color: initial; border-left-style: solid; border-left-color: blue; border-left-width: 1.5pt; padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 4pt; "><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; ">From:</span></b><span class="ececapple-converted-space"><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; "> </span></span><span style="font-size: 10pt; font-family: Tahoma, sans-serif; color: black; "><a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma-bounces@lists.mpi-forum.org</a><span class="ececapple-converted-space"> </span>[<a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mailto:mpi3-rma-bounces@lists.mpi-forum.org</a>]<span class="ececapple-converted-space"> </span><b>On Behalf Of<span class="ececapple-converted-space"> </span></b>Vinod tipparaju<br><b>Sent:</b><span class="ececapple-converted-space"> </span>Tuesday, September 01, 2009 5:23 AM<br><b>To:</b><span class="ececapple-converted-space"> </span>MPI 3.0 Remote Memory Access working group<br><b>Subject:</b><span class="ececapple-converted-space"> </span>Re: [Mpi3-rma] MPI3 RMA Design Goals</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Good points! RMA interfaces should do nothing to prevent utilizing a high message rate (or low overhead communication) that the underlying hardware may offer. To ensure this happens, there should always be a unrestricted path (lets call it this for now, people have called it a "thin layer", "direct access") to the network. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">This means, despite the fact the the RMA interface has features that abstract out complexity by providing useful characteristics such as ordering and atomicity, it (the RMA interface) should always have this unrestricted, close to the heart of the hardware, path. To achieve this, the unrestricted path should not require any book keeping (from implementation perspective) in relation to the feature-rich path or vice-versa. </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">I believe this is what we have demonstrated with the example interfaces hence the null set isn't the case here :-). I will distribute an example implementation very soon so people can get a feel.</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">---</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; color: black; ">Vinod Tipparaju ^<span class="ececapple-converted-space"> </span><a href="http://ft.ornl.gov/~vinod" style="color: blue; text-decoration: underline; ">http://ft.ornl.gov/~vinod</a><span class="ececapple-converted-space"> </span>^ 1-865-241-1802<br><br><br><br>> From:<span class="ececapple-converted-space"> </span><a href="mailto:keith.d.underwood@intel.com" style="color: blue; text-decoration: underline; ">keith.d.underwood@intel.com</a><br>> To:<span class="ececapple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>> Date: Mon, 31 Aug 2009 16:17:28 -0600<br>> Subject: Re: [Mpi3-rma] MPI3 RMA Design Goals<br>><span class="ececapple-converted-space"> </span><br>> There has been stunning silence since this email, so I will go ahead and toss out a thought...<br>><span class="ececapple-converted-space"> </span><br>> In the draft design goals, I don't see two issues that I see as key. The first is "support for high message rate/low overhead communications to random targets". As best I can tell, this is one of the key places were the existing one-sided operations are perceived as falling down for existing customers of SHMEM/PGAS. The second is "elimination of the access epoch requirement". This one may be, um, more controversial, but I believe it is part and parcel with the first one. That is, the first one is not that valuable if the programming model requires an excessive amount of access epoch opens and closes just to force the global visibility of the operations. Unfortunately, the intersection of this solution space with the solution space for the current draft design goal #5 (support non-cache-coherent and heterogeneous environments) may be the null set... I will hold out hope that this isn't the case ;-)<br>><span class="ececapple-converted-space"> </span><br>> Keith<span class="ececapple-converted-space"> </span><br>><span class="ececapple-converted-space"> </span><br>> > -----Original Message-----<br>> > From:<span class="Apple-converted-space"> </span><a href="mailto:mpi3-rma-bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma-bounces@lists.mpi-forum.org</a><span class="Apple-converted-space"> </span>[<a href="mailto:mpi3-rma-" style="color: blue; text-decoration: underline; ">mailto:mpi3-rma-</a><br>> ><span class="ececapple-converted-space"> </span><a href="mailto:bounces@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">bounces@lists.mpi-forum.org</a>] On Behalf Of William Gropp<br>> > Sent: Wednesday, August 05, 2009 12:37 PM<br>> > To:<span class="ececapple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>> > Subject: [Mpi3-rma] MPI3 RMA Design Goals<br>> ><span class="ececapple-converted-space"> </span><br>> > I've added versions of the RMA design goals that we discussed at the<br>> > Forum meeting last week to the wiki page for our group (<br>> ><span class="ececapple-converted-space"> </span><a href="https://svn.mpi-forum.org/trac/mpi-forum-web/wiki/RmaWikiPage" style="color: blue; text-decoration: underline; ">https://svn.mpi-forum.org/trac/mpi-forum-web/wiki/RmaWikiPage</a><br>> > ). This is a draft; lets discuss these. Also, feel free to add to<br>> > the discussion, particularly in the background section.<br>> ><span class="ececapple-converted-space"> </span><br>> > Bill<br>> ><span class="ececapple-converted-space"> </span><br>> > William Gropp<br>> > Deputy Director for Research<br>> > Institute for Advanced Computing Applications and Technologies<br>> > Paul and Cynthia Saylor Professor of Computer Science<br>> > University of Illinois Urbana-Champaign<br>> ><span class="ececapple-converted-space"> </span><br>> ><span class="ececapple-converted-space"> </span><br>> ><span class="ececapple-converted-space"> </span><br>> ><span class="ececapple-converted-space"> </span><br>> > _______________________________________________<br>> > mpi3-rma mailing list<br>> ><span class="ececapple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>> ><span class="ececapple-converted-space"> </span><a href="http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma" style="color: blue; text-decoration: underline; ">http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma</a><br>><span class="ececapple-converted-space"> </span><br>> _______________________________________________<br>> mpi3-rma mailing list<br>><span class="ececapple-converted-space"> </span><a href="mailto:mpi3-rma@lists.mpi-forum.org" style="color: blue; text-decoration: underline; ">mpi3-rma@lists.mpi-forum.org</a><br>><span class="ececapple-converted-space"> </span><a href="http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma" style="color: blue; text-decoration: underline; ">http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma</a></span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div></div></div></div></div></div></div></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 13.5pt; font-family: Helvetica, sans-serif; color: black; "><ATT00001.txt></span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div></blockquote></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div><div><div><div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">William Gropp</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">Deputy Director for Research</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">Institute for Advanced Computing Applications and Technologies</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">Paul and Cynthia Saylor Professor of Computer Science</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; ">University of Illinois Urbana-Champaign</span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div><div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 9pt; font-family: Helvetica, sans-serif; color: black; "> </span><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p></o:p></span></div></div></div><p class="MsoNormal" style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 12pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "><o:p> </o:p></span></p></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div></div><div style="margin-right: 0in; margin-left: 0in; font-size: 12pt; font-family: 'Times New Roman', serif; margin-top: 0in; margin-bottom: 0.0001pt; "><span style="font-size: 10pt; font-family: Verdana, sans-serif; "> <o:p></o:p></span></div></div></div></div></div><span><ATT00001.txt></span></div></div></span></blockquote></div><br><div> <span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><span class="Apple-style-span" style="border-collapse: separate; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; -webkit-text-decorations-in-effect: none; text-indent: 0px; -webkit-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>William Gropp</div><div>Deputy Director for Research</div><div>Institute for Advanced Computing Applications and Technologies</div><div>Paul and Cynthia Saylor Professor of Computer Science</div><div>University of Illinois Urbana-Champaign</div><div><br class="khtml-block-placeholder"></div></div><br class="Apple-interchange-newline"></span></div></span><br class="Apple-interchange-newline"> </div><br></div></body></html>