[Mpiwg-large-counts] Large Count - the principles for counts, sizes, and byte and nonbyte displacements
Jeff Hammond
jeff.science at gmail.com
Thu Oct 31 10:34:37 CDT 2019
On Thu, Oct 31, 2019 at 7:48 AM Rolf Rabenseifner <rabenseifner at hlrs.de>
wrote:
> Dear all,
>
> here my summary as input for our telcon today.
>
> In principle, it is a very simple question:
>
> with large Counts, do we
> - keep all MPI_Aint
> - or do we substitute MPI_Aint by MPI_Count?
>
I haven't been involved as much lately but did we not use MPI_Count for
count and element displacements in the large count proposal? We need to
use MPI_Aint for offsets into memory because that is what this type is for.
Jeff
>
> In principle, the MPI Forum answered this question already
> for MPI-3.0 in 2012 with a clear YES:
>
> int MPI_Type_get_extent(MPI_Datatype datatype,
> MPI_Aint *lb, MPI_Aint *extent)
> int MPI_Type_get_extent_x(MPI_Datatype datatype,
> MPI_Count *lb, MPI_Count *extent)
>
> About Jeff H. question:
> If we limit the API to not support MPI_Count
> means that an MPI implementation has not really such quality options
> when using I/O fileviews, because the API is restricted to
> MPI_Aint (which should be implemented based on the, e.g.,
> 64bit memory system).
>
> About Jim's comment:
>
> >> Apologies, it's been a while since I looked at the I/O interfaces. If
> I/O
> >> only needs relative displacements that have normal integer semantics,
> then
> >> I don't see why MPI_Count would not work for this purpose. If you have
> an
> >> MPI_Aint that contains a relative displacement, it also has normal
> integer
> >> semantics and can be converted to an MPI_Count.
>
> Yes, but this automatically implies that the datatypes must also
> be able to handle MPI_Count.
>
> >> The only case we really
> >> need to look out for is when an integer type contains an absolute
> address.
> >> In those cases, the quantity in the variable cannot be treated as a
> normal
> >> integer and we need special routines to work with it.
>
> Yes, this happens when we extend MPI_Aint in the derived datatype routines
> to MPI_Count.
>
> But in principle, this is not a big Problem, as you all could see in
> the previous emails:
>
> - We must do for MPI_Count the same as we did for MPI_Aint,
> i.e., we'll have long versions of the routines
> MPI_Get_address, MPI_Aint_diff, MPI_Aint_add
>
> - And we must ensure that the type cast from MPI_Aint to
> MPI_Count works, which is a small new advice to implementors
> for MPI_Det_address.
>
> Therefore again my 4 questions:
>
> - Should the new large count routines be prepared for
> more than 10 or 20 Exabyte files where we need 64/65 or
> or 65/66 unsigned/signed integers for relative byte
> displacements or byte counts?
> If yes, then all MPI_Aint arguments must be substituted by MPI_Count.
>
> (In other words, do we want to be prepared for another 25 years of MPI?
> :-)
>
> As stated above, the MPI-Forum already decided 2012 with a YES.
>
> - Should we allow that these new routines are also used for memory
> description,
> where we typically need only the large MPI_Count "count" arguments?
> (or should we provide two different new routines for each routine that
> currently has int Count/... and MPI_Aint disp/... arguments)
>
> I expect, that nobody wants to have two different large versions of
> for example MPI_Type_create_struct.
>
> - Should we allow a mix of old and new routines, especially for
> memory-based
> usage, that old-style MPI_Get_address is used to retrieve an absolute
> address and then, e.g., new style MPI_Type_create_struct with
> MPI_Count blocklength and displacements is used?
>
> I expect that forbidding such a mix would be a problem for Software
> development.
> Often old-style modules must work together with new-style modules.
>
> - Do we want to require for this type cast of MPI_Aint addr into MPI_Count
> that it is allowed to do this cast with a normal assignment, rather
> than
> a special MPI function?
>
> I expect yes, because for must usage of MPI_Aint and MPI_Count,
> it is for relative displacements or byte counts, i.e. for normal
> integers and therefore automatic type cast between MPI_Aint
> and MPI_Count is a must.
>
> With yes to all four questions, the proposed solution above is
> the easiest way.
>
> Hope to see/hear you today in our telcon.
>
> Best regards
> Rolf
>
>
> ----- Original Message -----
> > From: "Jeff Hammond" <jeff.science at gmail.com>
> > To: "mpiwg-large-counts" <mpiwg-large-counts at lists.mpi-forum.org>
> > Cc: "Rolf Rabenseifner" <rabenseifner at hlrs.de>, "Jim Dinan" <
> james.dinan at gmail.com>
> > Sent: Thursday, October 31, 2019 5:58:30 AM
> > Subject: Re: [Mpiwg-large-counts] Large Count - the principles for
> counts, sizes, and byte and nonbyte displacements
>
> > What if we just decided not to support IO displacements bigger than 2^63?
> > What use case would that break? If the underlying filesystem uses 128b
> > displacements, fine, then MPI will promote into those before using the
> > system APIs.
> >
> > We already limit all sorts of things. For example, posting 17 billion
> > Isends is not guaranteed to work. Maybe it does, but that's a quality of
> > implementation issue. No sane person is going to have a data type
> spanning
> > 8 exabyte increments. Not now, not in 2030, not in 2040, not ever.
> >
> > Jeff
> >
> > On Wed, Oct 30, 2019 at 9:10 AM Jim Dinan via mpiwg-large-counts <
> > mpiwg-large-counts at lists.mpi-forum.org> wrote:
> >
> >> Apologies, it's been a while since I looked at the I/O interfaces. If
> I/O
> >> only needs relative displacements that have normal integer semantics,
> then
> >> I don't see why MPI_Count would not work for this purpose. If you have
> an
> >> MPI_Aint that contains a relative displacement, it also has normal
> integer
> >> semantics and can be converted to an MPI_Count. The only case we really
> >> need to look out for is when an integer type contains an absolute
> address.
> >> In those cases, the quantity in the variable cannot be treated as a
> normal
> >> integer and we need special routines to work with it. If MPI never
> treats
> >> an MPI_Count quantity as an absolute address then MPI_Count should
> always
> >> have normal integer semantics via the MPI interfaces and doesn't need
> >> special treatment. Unless, of course, we want to enable MPI_Count that
> is
> >> large enough to need special support for basic operations, but that's a
> >> different can of worms.
> >>
> >> ~Jim.
> >>
> >> On Wed, Oct 30, 2019 at 11:02 AM Rolf Rabenseifner <
> rabenseifner at hlrs.de>
> >> wrote:
> >>
> >>> Dear Jim,
> >>>
> >>> > This sounds to me like it is creating again the same problem we have
> >>> with
> >>> > MPI_Aint --- one type doing too many things. If MPI_Aint can't
> >>> accommodate
> >>> > absolute addresses in the I/O interfaces,
> >>>
> >>> I/O has no absolute addresses. Only relative one, i.e., byte
> >>> displacements
> >>> and byte sizes.
> >>> But they can be huge.
> >>>
> >>> The same routines are used for message passing, for example
> >>> - MPI_TYPE_CREATE_STRUCT or
> >>> - MPI_TYPE_CREATE_RESIZED
> >>>
> >>> > we should consider adding a new
> >>> > type like MPI_Faint (file address int) for this quantity and include
> >>> > accessor routines to ensure manipulations of file addresses respect
> the
> >>> > implementation defined meaning of the bits.
> >>>
> >>> Yes, you are right, there are two possibilities:
> >>> Substitute MPI_Aint in the large count version by
> >>> - MPI_Count or
> >>> - or by a new type MPI_Laint (for Long Aint)
> >>>
> >>> Others on this list have already expressed that they never want to see
> >>> such a MPI_Laint
> >>>
> >>> > Even in C, it is not portable
> >>> > to do arithmetic on intptr_t because the integer representation of an
> >>> > address is implementation defined. We were careful in the
> definition of
> >>> > MPI_Aint_add and diff to describe them in terms of casting the
> absolute
> >>> > address arguments back to pointers before performing arithmetic.
> >>>
> >>> Yes, therefore, for this longer Version of MPI_Aint, let's name it
> >>> for the Moment XXX, we Need
> >>> MPI_XXX_diff and MPI_XXX_add,
> >>> i.e. MPI_Laint_diff and _add or MPI_Count_diff and _add,
> >>> which should be used only if the corresponding addresses
> >>> are returned from MPI_Get_address_l.
> >>> Or form MPI_Get_address, and with this we have again the
> >>> type casting problem between MPI_Aint and MPI_Count or MPI_Laint.
> >>>
> >>> Best regards
> >>> Rolf
> >>>
> >>> ----- Original Message -----
> >>> > From: "Jim Dinan" <james.dinan at gmail.com>
> >>> > To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> >>> > Cc: "mpiwg-large-counts" <mpiwg-large-counts at lists.mpi-forum.org>
> >>> > Sent: Wednesday, October 30, 2019 3:45:01 PM
> >>> > Subject: Re: [Mpiwg-large-counts] Large Count - the principles for
> >>> counts, sizes, and byte and nonbyte displacements
> >>>
> >>> > This sounds to me like it is creating again the same problem we have
> >>> with
> >>> > MPI_Aint --- one type doing too many things. If MPI_Aint can't
> >>> accommodate
> >>> > absolute addresses in the I/O interfaces, we should consider adding a
> >>> new
> >>> > type like MPI_Faint (file address int) for this quantity and include
> >>> > accessor routines to ensure manipulations of file addresses respect
> the
> >>> > implementation defined meaning of the bits. Even in C, it is not
> >>> portable
> >>> > to do arithmetic on intptr_t because the integer representation of an
> >>> > address is implementation defined. We were careful in the
> definition of
> >>> > MPI_Aint_add and diff to describe them in terms of casting the
> absolute
> >>> > address arguments back to pointers before performing arithmetic.
> >>> >
> >>> > ~Jim.
> >>> >
> >>> > On Wed, Oct 30, 2019 at 5:18 AM Rolf Rabenseifner <
> rabenseifner at hlrs.de
> >>> >
> >>> > wrote:
> >>> >
> >>> >> Dear all and Jim,
> >>> >>
> >>> >> Jim asked:
> >>> >> > When you assign an MPI_Aint to an MPI_Count, there are two cases
> >>> >> depending
> >>> >> > on what the bits in the MPI_Aint represent: absolute address and
> >>> relative
> >>> >> > displacements. The case where you assign an address to a count
> >>> doesn't
> >>> >> > make sense to me. Why would one do this and why should MPI
> support
> >>> it?
> >>> >> > The case where you assign a displacement to a count seems fine,
> you
> >>> would
> >>> >> > want sign extension to happen.
> >>> >>
> >>> >> The answer is very simple:
> >>> >> All derived datatype routines serve describing of memory **and**
> file
> >>> >> space.
> >>> >>
> >>> >> Therefore, the large count working group should decide:
> >>> >> - Should the new large count routines be prepared for more than 10
> or
> >>> 20
> >>> >> Exabyte
> >>> >> files where we need 64/65 or 65/66 unsigned/signed integers for
> >>> relative
> >>> >> byte
> >>> >> displacements or byte counts?
> >>> >> If yes, then all MPI_Aint arguments must be substituted by
> MPI_Count.
> >>> >> (In other words, do we want to be prepared for another 25 years of
> >>> MPI?
> >>> >> :-)
> >>> >> - Should we allow that these new routines are also used for memory
> >>> >> description,
> >>> >> where we typically need only the large MPI_Count "count"
> arguments?
> >>> >> (or should we provide two different new routines for each routine
> >>> that
> >>> >> currently has int Count/... and MPI_Aint disp/... arguments)
> >>> >> - Should we allow a mix of old and new routines, especially for
> >>> >> memory-based
> >>> >> usage, that old-style MPI_Get_address is used to retrieve an
> absolute
> >>> >> address and then, e.g., new style MPI_Type_create_struct with
> >>> >> MPI_Count blocklength and displacements is used?
> >>> >> - Do we want to require for this type cast of MPI_Aint addr into
> >>> MPI_Count
> >>> >> that it is allowed to do this cast with a normal assignment,
> rather
> >>> than
> >>> >>
> >>> >> a special MPI function?
> >>> >>
> >>> >> If we answer all four questions with yes (and in my opinion, we
> must)
> >>> >> then Jim's question
> >>> >> "Why would one do this [assign an address to a Count]
> >>> >> and why should MPI support it?"
> >>> >> is answered with this set of reasons.
> >>> >>
> >>> >> I would say, that this is the most complex decision that the
> >>> >> large count working group has to decide.
> >>> >> A wrong decision would be hard to be fixed in the future.
> >>> >>
> >>> >> Best regards
> >>> >> Rolf
> >>> >>
> >>> >> ----- Original Message -----
> >>> >> > From: "Jim Dinan" <james.dinan at gmail.com>
> >>> >> > To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> >>> >> > Cc: "mpiwg-large-counts" <mpiwg-large-counts at lists.mpi-forum.org>
> >>> >> > Sent: Tuesday, October 29, 2019 10:28:46 PM
> >>> >> > Subject: Re: [Mpiwg-large-counts] Large Count - the principles for
> >>> >> counts, sizes, and byte and nonbyte displacements
> >>> >>
> >>> >> > If you do pointer arithmetic, the compiler will ensure that the
> >>> result is
> >>> >> > correct. If you convert a pointer into an integer and then do the
> >>> >> > arithmetic, the compiler can't help you and the result is not
> >>> portable.
> >>> >> > This is why MPI_Aint_add describes what it does in terms of
> pointer
> >>> >> > arithmetic. The confusing and frustrating thing about MPI_Aint is
> >>> that
> >>> >> > it's one type for two very different purposes. Allowing direct
> +/-
> >>> on
> >>> >> > MPI_Aint values that represent addresses is not portable and is a
> >>> mistake
> >>> >> > that we tried to correct with MPI_Aint_add/diff (I am happy to
> >>> strengthen
> >>> >> > should to must if needed). It's perfectly fine to do arithmetic
> on
> >>> >> > MPI_Aint values that are displacements.
> >>> >> >
> >>> >> > When you assign an MPI_Aint to an MPI_Count, there are two cases
> >>> >> depending
> >>> >> > on what the bits in the MPI_Aint represent: absolute address and
> >>> relative
> >>> >> > displacements. The case where you assign an address to a count
> >>> doesn't
> >>> >> > make sense to me. Why would one do this and why should MPI
> support
> >>> it?
> >>> >> > The case where you assign a displacement to a count seems fine,
> you
> >>> would
> >>> >> > want sign extension to happen.
> >>> >> >
> >>> >> > ~Jim.
> >>> >> >
> >>> >> > On Tue, Oct 29, 2019 at 4:52 PM Rolf Rabenseifner <
> >>> rabenseifner at hlrs.de>
> >>> >> > wrote:
> >>> >> >
> >>> >> >> Dear Jim,
> >>> >> >>
> >>> >> >> > (a3) Section 4.1.5 of MPI 3.1 states "To ensure portability,
> >>> >> arithmetic
> >>> >> >> on
> >>> >> >> > absolute addresses should not be performed with the intrinsic
> >>> >> operators
> >>> >> >> \-"
> >>> >> >> > and \+".
> >>> >> >>
> >>> >> >> The major problem is, that we decided "should" and not "maust" or
> >>> >> "shall",
> >>> >> >> because there is such many existing MPI-1 ... MPI-3.0 code that
> must
> >>> >> have
> >>> >> >> used + or - operators.
> >>> >> >>
> >>> >> >> The only objective, that is true from the beginning, that MPI
> >>> addresses
> >>> >> >> must be
> >>> >> >> retrieved with MPI_Get_address.
> >>> >> >>
> >>> >> >> And the second also Major Problem is the new assigment of an
> >>> MPI_Aint
> >>> >> >> value
> >>> >> >> into an MPI_Count variable with MPI_Count larger than MPI_Aint.
> >>> >> >>
> >>> >> >> Therefore, I would prefere, that we keep this "should" and
> design in
> >>> >> long
> >>> >> >> term
> >>> >> >> MPI_Get_address in a way that in principle MPI_Aint_diff and _add
> >>> >> >> need not to do anythin else as the + or - operator.
> >>> >> >>
> >>> >> >> And this depends on the meaning of the unsigned addresses, i.e.,
> >>> >> >> what is the sequence of addresses (i.e., is it really going from
> >>> >> >> 0 to FFFF...FFFF) and than mapping these addreses to the
> >>> mathematical
> >>> >> >> sequence
> >>> >> >> of MPI_Aint which starts at -2**(n-1) and ends at 2**(n-1)-1.
> >>> >> >>
> >>> >> >> Thats all. For the moment, as far as the web and some emails told
> >>> us,
> >>> >> >> we are fare away from this contiguous 64-bit address space (0 to
> >>> >> >> FFFF...FFFF).
> >>> >> >>
> >>> >> >> But we should be correctly prepared.
> >>> >> >>
> >>> >> >> Or in other words:
> >>> >> >> > (a2) Should be solved by MPI_Aint_add/diff.
> >>> >> >> In my opinion no, it must be solved by MPI_Get_addr
> >>> >> >> and MPI_Aint_add/diff can stay normal + or - operators.
> >>> >> >>
> >>> >> >> I should also mention, that of course all MPI routines that
> >>> >> >> accept MPI_BOOTOM must reverse the work of MPI_Get_address
> >>> >> >> to get back the real "unsigned" virtual addresses of the OS.
> >>> >> >>
> >>> >> >> The same what we already had if an implementation has chosen
> >>> >> >> to use the address of an MPI common block as base for MPI_BOTTOM.
> >>> >> >> Here, the MPI lib had the freedom to revert the mapping
> >>> >> >> within MPI_Get_addr or within all functions called with
> MPI_BOTTOM.
> >>> >> >>
> >>> >> >> Best regards
> >>> >> >> Rolf
> >>> >> >>
> >>> >> >>
> >>> >> >>
> >>> >> >> ----- Original Message -----
> >>> >> >> > From: "Jim Dinan" <james.dinan at gmail.com>
> >>> >> >> > To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> >>> >> >> > Cc: "mpiwg-large-counts" <
> mpiwg-large-counts at lists.mpi-forum.org>
> >>> >> >> > Sent: Tuesday, October 29, 2019 3:58:18 PM
> >>> >> >> > Subject: Re: [Mpiwg-large-counts] Large Count - the principles
> for
> >>> >> >> counts, sizes, and byte and nonbyte displacements
> >>> >> >>
> >>> >> >> > Hi Rolf,
> >>> >> >> >
> >>> >> >> > (a1) seems to me like another artifact of storing an unsigned
> >>> quantity
> >>> >> >> in a
> >>> >> >> > signed variable, i.e., the quantity in an MPI_Aint can be an
> >>> unsigned
> >>> >> >> > address or a signed displacement. Since we don't have an
> unsigned
> >>> >> type
> >>> >> >> for
> >>> >> >> > addresses, the user can't portably fix this above MPI. We will
> >>> need
> >>> >> to
> >>> >> >> add
> >>> >> >> > functions to deal with combinations of MPI_Aint and MPI_Counts.
> >>> This
> >>> >> is
> >>> >> >> > essentially why we needed MPI_Aint_add/diff. Or ... the golden
> >>> (Au is
> >>> >> >> > gold) int ... MPI_Auint.
> >>> >> >> >
> >>> >> >> > (a2) Should be solved by MPI_Aint_add/diff.
> >>> >> >> >
> >>> >> >> > (a3) Section 4.1.5 of MPI 3.1 states "To ensure portability,
> >>> >> arithmetic
> >>> >> >> on
> >>> >> >> > absolute addresses should not be performed with the intrinsic
> >>> >> operators
> >>> >> >> \-"
> >>> >> >> > and \+". MPI_Aint_add was written carefully to indicate that
> the
> >>> >> "base"
> >>> >> >> > argument is treated as an unsigned address and the "disp"
> >>> argument is
> >>> >> >> > treated as a signed displacement.
> >>> >> >> >
> >>> >> >> > ~Jim.
> >>> >> >> >
> >>> >> >> > On Tue, Oct 29, 2019 at 5:19 AM Rolf Rabenseifner <
> >>> >> rabenseifner at hlrs.de>
> >>> >> >> > wrote:
> >>> >> >> >
> >>> >> >> >> Dear Jim and all,
> >>> >> >> >>
> >>> >> >> >> I'm not sure whether I'm really able to understand your email.
> >>> >> >> >>
> >>> >> >> >> I take the MPI view:
> >>> >> >> >>
> >>> >> >> >> (1) An absolute address can stored in an MPI_Aint variable
> >>> >> >> >> with and only with MPI_Get_address or MPI_Aint_add.
> >>> >> >> >>
> >>> >> >> >> (2) A positive or negative number of bytes or a relative
> address
> >>> >> >> >> which is by definition the amount of bytes between two
> >>> locations
> >>> >> >> >> in a MPI "sequential storage" (MPI-3.1 page 115)
> >>> >> >> >> can be assigned with any method to an MPI_Aint variable
> >>> >> >> >> as long as the original value fits into MPI_Aint.
> >>> >> >> >> In both languages automatic type cast (i.e., sign
> expansion)
> >>> >> >> >> is done.
> >>> >> >> >>
> >>> >> >> >> (3) If users misuse MPI_Aint for storing anything else into
> >>> MPI_Aint
> >>> >> >> >> variable then this is out of scope of MPI.
> >>> >> >> >> If such values are used in a minus operation then it is
> >>> >> >> >> out of the scope of MPI whether this makes sense.
> >>> >> >> >> If the user is sure that the new value falls into category
> >>> (2)
> >>> >> >> >> then all is fine as long as the user is correct.
> >>> >> >> >>
> >>> >> >> >> I expect that your => is not a "greater or equal than".
> >>> >> >> >> I expect that you noticed assignments.
> >>> >> >> >>
> >>> >> >> >> > intptr_t => MPI_Aint
> >>> >> >> >> "intptr_t: integer type capable of holding a pointer."
> >>> >> >> >>
> >>> >> >> >> > uintptr_t => ??? (Anyone remember the MPI_Auint "golden
> Aint"
> >>> >> >> proposal?)
> >>> >> >> >> "uintptr_t: unsigned integer type capable of holding a
> pointer."
> >>> >> >> >>
> >>> >> >> >> may fall exactly exactly into (3) when used for pointers.
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> Especially on a 64 bit system the user may have in the future
> >>> exactly
> >>> >> >> >> the problems (a), (a1), (a2) and (b) as described below.
> >>> >> >> >> But here, the user is responsible, to for example implement
> (a3),
> >>> >> >> >> whereas for MPI_Get_address, the implementors of the MPI
> library
> >>> >> >> >> are responsible and the MPI Forum may be responsible for
> giving
> >>> >> >> >> the correct advices.
> >>> >> >> >>
> >>> >> >> >> By the way, the golden MPI_Auint was never golden.
> >>> >> >> >> Such need was "resolved" by introducing MPI_Aint_diff and
> >>> >> MPI_Aint_add
> >>> >> >> >> in MPI-3.1.
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> > ptrdiff_t => MPI_Aint
> >>> >> >> >> "std::ptrdiff_t is the signed integer type of the result of
> >>> >> subtracting
> >>> >> >> >> two pointers."
> >>> >> >> >>
> >>> >> >> >> may perfectly fit to (2).
> >>> >> >> >>
> >>> >> >> >> All of the following falls into category (2):
> >>> >> >> >>
> >>> >> >> >> > size_t (sizeof) => MPI_Count, int
> >>> >> >> >> "sizeof( type ) (1)
> >>> >> >> >> sizeof expression (2)
> >>> >> >> >> Both versions are constant expressions of type std::size_t."
> >>> >> >> >>
> >>> >> >> >> > size_t (offsetof) => MPI_Aint, int
> >>> >> >> >> "Defined in header <cstddef>
> >>> >> >> >> #define offsetof(type, member) /*implementation-defined*/
> >>> >> >> >> The macro offsetof expands to an integral constant expression
> >>> >> >> >> of type std::size_t, the value of which is the offset, in
> bytes,
> >>> >> >> >> from the beginning of an object of specified type to ist
> >>> >> >> >> specified member, including padding if any."
> >>> >> >> >>
> >>> >> >> >> Note that this offsetof has nothing to do with MPI_Offset.
> >>> >> >> >>
> >>> >> >> >> On a system with less than 2*31 byte and 4-byte int, it is
> >>> guaranteed
> >>> >> >> >> that size_t => int works.
> >>> >> >> >>
> >>> >> >> >> On a system with less than 2*63 byte and 8-byte MPI_Aint, it
> is
> >>> >> >> guaranteed
> >>> >> >> >> that size_t => MPI_Aint works.
> >>> >> >> >>
> >>> >> >> >> Problem: size_t is unsigned, int and MPI_Aint are signed.
> >>> >> >> >>
> >>> >> >> >> MPI_Count should be defined in a way that on systems with more
> >>> than
> >>> >> >> >> 2**63 Bytes of disc space, that MPI_Count can hold such
> values,
> >>> >> >> >> because
> >>> >> >> >> int .LE. {MPI_Aint, MPI_Offset} .LE. MPI_Count
> >>> >> >> >>
> >>> >> >> >> Therefore size_t => MPI_Count should always work.
> >>> >> >> >>
> >>> >> >> >> > ssize_t => Mostly for error handling. Out of scope for MPI?
> >>> >> >> >> "In short, ssize_t is the same as size_t, but is a signed
> type -
> >>> >> >> >> read ssize_t as “signed size_t”. ssize_t is able to represent
> >>> >> >> >> the number -1, which is returned by several system calls
> >>> >> >> >> and library functions as a way to indicate error.
> >>> >> >> >> For example, the read and write system calls: ...
> >>> >> >> >> ssize_t read(int fildes, void *buf, size_t nbyte); ..."
> >>> >> >> >>
> >>> >> >> >> ssize_t fits therefore better to MPI_Aint, because both
> >>> >> >> >> are signed types that can hold byte counts, but
> >>> >> >> >> the value -1 in a MPI_Aint variable stands for a
> >>> >> >> >> byte displacement of -1 bytes and not for an error code -1.
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> All use of (2) is in principle no problem.
> >>> >> >> >> ------------------------------------------
> >>> >> >> >>
> >>> >> >> >> All the complex discussiuon of the last days is about (1):
> >>> >> >> >>
> >>> >> >> >> (1) An absolute address can stored in an MPI_Aint variable
> >>> >> >> >> with and only with MPI_Get_address or MPI_Aint_add.
> >>> >> >> >>
> >>> >> >> >> In MPI-1 to MPI-3.0 and still in MPI-3.1 (here as may be not
> >>> >> portable),
> >>> >> >> >> we also allow
> >>> >> >> >> MPI_Aint variable := absolute address in MPI_Aint variable
> >>> >> >> >> + or -
> >>> >> >> >> a number of bytes (in any integer type).
> >>> >> >> >>
> >>> >> >> >> The result is then still in category (1).
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> For the difference of two absolute addresses,
> >>> >> >> >> MPI_Aint_diff can be used. The result is than MPI_Aint of
> >>> category
> >>> >> (2)
> >>> >> >> >>
> >>> >> >> >> In MPI-1 to MPI-3.0 and still in MPI-3.1 (here as may be not
> >>> >> portable),
> >>> >> >> >> we also allow
> >>> >> >> >> MPI_Aint variable := absolute address in MPI_Aint variable
> >>> >> >> >> - absolute address in MPI_Aint variable.
> >>> >> >> >>
> >>> >> >> >> The result is then in category (2).
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> The problems we discuss the last days are about systems
> >>> >> >> >> that internally use unsigned addresses and the MPI library
> stores
> >>> >> >> >> these addresses into MPI_Aint variables and
> >>> >> >> >>
> >>> >> >> >> (a) a sequential storage can have virtual addresses that
> >>> >> >> >> are both in the area with highest bit =0 and other
> addresses
> >>> >> >> >> in the same sequential storage (i.e., same array or
> >>> structure)
> >>> >> >> >> with highest bit =1.
> >>> >> >> >>
> >>> >> >> >> or
> >>> >> >> >> (b) some higher bits contain segment addresses.
> >>> >> >> >>
> >>> >> >> >> (b) is not a problem as long as a sequential storage resides
> >>> >> >> >> always within one Segment.
> >>> >> >> >>
> >>> >> >> >> Therefore, we only have to discuss (a).
> >>> >> >> >>
> >>> >> >> >> The two problems that we have is
> >>> >> >> >> (a1) that for the minus operations an integer overflow will
> >>> >> >> >> happen and must be ignored.
> >>> >> >> >> (a2) if such addresses are expanded to larger variables,
> >>> >> >> >> e.g., MPI_Count with more bits in MPI_Count than in
> >>> MPI_Aint,
> >>> >> >> >> sign expansion will result in completely wring results.
> >>> >> >> >>
> >>> >> >> >> And here, the most simple trick is,
> >>> >> >> >> (a3) that MPI_Get_address really shall
> >>> >> >> >> map the contiguous unsigned range from 0 to 2**64-1 to the
> >>> >> >> >> signed (and also contiguous) range from -2**63 to 2**63-1
> >>> >> >> >> by simple subtracting 2**63.
> >>> >> >> >> With this simple trick in MPI_Get_address, Problems
> >>> >> >> >> 8a1) and (a2) are resolved.
> >>> >> >> >>
> >>> >> >> >> It looks like that (a) and therefore (a1) and (a2)
> >>> >> >> >> may be far in the future.
> >>> >> >> >> But they may be less far in the future, if a system may
> >>> >> >> >> map the whole applications cluster address space
> >>> >> >> >> into virtual memory (not cache coherent, but accessible).
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> And all this is never or only partial written into the
> >>> >> >> >> MPI Standard, also all is (well) known by the MPI Forum,
> >>> >> >> >> with the following exceptions:
> >>> >> >> >> - (a2) is new.
> >>> >> >> >> - (a1) is solved in MPI-3.1 only for MPI_Aint_diff and
> >>> >> >> >> MPI_Aint_add, but not for the operators - and +
> >>> >> >> >> if a user will switch on integer overflow detection
> >>> >> >> >> in the future when we will have such large systems.
> >>> >> >> >> - (a3) is new and in principle solves the problem also
> >>> >> >> >> for + and - operators.
> >>> >> >> >>
> >>> >> >> >> At lease (a1)+(a2) should be added as rationale to MPI-4.0
> >>> >> >> >> and (a3) as advice to implementors within the framework
> >>> >> >> >> of big count, because (a2) is newly coming with big count.
> >>> >> >> >>
> >>> >> >> >> I hope this helps a bit if you took the time to read
> >>> >> >> >> this long email.
> >>> >> >> >>
> >>> >> >> >> Best regards
> >>> >> >> >> Rolf
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >>
> >>> >> >> >> ----- Original Message -----
> >>> >> >> >> > From: "mpiwg-large-counts" <
> >>> mpiwg-large-counts at lists.mpi-forum.org
> >>> >> >
> >>> >> >> >> > To: "mpiwg-large-counts" <
> >>> mpiwg-large-counts at lists.mpi-forum.org>
> >>> >> >> >> > Cc: "Jim Dinan" <james.dinan at gmail.com>, "James Dinan" <
> >>> >> >> >> james.dinan at intel.com>
> >>> >> >> >> > Sent: Monday, October 28, 2019 5:07:37 PM
> >>> >> >> >> > Subject: Re: [Mpiwg-large-counts] Large Count - the
> principles
> >>> for
> >>> >> >> >> counts, sizes, and byte and nonbyte displacements
> >>> >> >> >>
> >>> >> >> >> > Still not sure I see the issue. MPI's memory-related
> integers
> >>> >> should
> >>> >> >> map
> >>> >> >> >> to
> >>> >> >> >> > types that serve the same function in C. If the base
> language
> >>> is
> >>> >> >> broken
> >>> >> >> >> for
> >>> >> >> >> > segmented addressing, we won't be able to fix it in a
> library.
> >>> >> Looking
> >>> >> >> >> at the
> >>> >> >> >> > mapping below, I don't see where we would have broken it:
> >>> >> >> >> >
> >>> >> >> >> > intptr_t => MPI_Aint
> >>> >> >> >> > uintptr_t => ??? (Anyone remember the MPI_Auint "golden
> Aint"
> >>> >> >> proposal?)
> >>> >> >> >> > ptrdiff_t => MPI_Aint
> >>> >> >> >> > size_t (sizeof) => MPI_Count, int
> >>> >> >> >> > size_t (offsetof) => MPI_Aint, int
> >>> >> >> >> > ssize_t => Mostly for error handling. Out of scope for MPI?
> >>> >> >> >> >
> >>> >> >> >> > It sounds like there are some places where we used MPI_Aint
> in
> >>> >> place
> >>> >> >> of
> >>> >> >> >> size_t
> >>> >> >> >> > for sizes. Not great, but MPI_Aint already needs to be at
> >>> least as
> >>> >> >> large
> >>> >> >> >> as
> >>> >> >> >> > size_t, so this seems benign.
> >>> >> >> >> >
> >>> >> >> >> > ~Jim.
> >>> >> >> >> >
> >>> >> >> >> > On Fri, Oct 25, 2019 at 8:25 PM Dinan, James via
> >>> >> mpiwg-large-counts <
> >>> >> >> [
> >>> >> >> >> > mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ] > wrote:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jeff, thanks so much for opening up these old wounds. I’m
> not
> >>> sure
> >>> >> I
> >>> >> >> >> have enough
> >>> >> >> >> > context to contribute to the discussion. Where can I read up
> >>> on the
> >>> >> >> >> issue with
> >>> >> >> >> > MPI_Aint?
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > I’m glad to hear that C signed integers will finally have a
> >>> >> >> well-defined
> >>> >> >> >> > representation.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > ~Jim.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > From: Jeff Hammond < [ mailto:jeff.science at gmail.com |
> >>> >> >> >> jeff.science at gmail.com ]
> >>> >> >> >> > >
> >>> >> >> >> > Date: Thursday, October 24, 2019 at 7:03 PM
> >>> >> >> >> > To: "Jeff Squyres (jsquyres)" < [ mailto:jsquyres at cisco.com
> |
> >>> >> >> >> jsquyres at cisco.com
> >>> >> >> >> > ] >
> >>> >> >> >> > Cc: MPI BigCount Working Group < [ mailto:
> >>> >> >> >> mpiwg-large-counts at lists.mpi-forum.org
> >>> >> >> >> > | mpiwg-large-counts at lists.mpi-forum.org ] >, "Dinan,
> James"
> >>> < [
> >>> >> >> >> > mailto:james.dinan at intel.com | james.dinan at intel.com ] >
> >>> >> >> >> > Subject: Re: [Mpiwg-large-counts] Large Count - the
> principles
> >>> for
> >>> >> >> >> counts,
> >>> >> >> >> > sizes, and byte and nonbyte displacements
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jim (cc) suffered the most in MPI 3.0 days because of
> >>> AINT_DIFF and
> >>> >> >> >> AINT_SUM, so
> >>> >> >> >> > maybe he wants to create this ticket.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jeff
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > On Thu, Oct 24, 2019 at 2:41 PM Jeff Squyres (jsquyres) < [
> >>> >> >> >> > mailto:jsquyres at cisco.com | jsquyres at cisco.com ] > wrote:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Not opposed to ditching segmented addressing at all. We'd
> need
> >>> a
> >>> >> >> ticket
> >>> >> >> >> for this
> >>> >> >> >> > ASAP, though.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > This whole conversation is predicated on:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > - MPI supposedly supports segmented addressing
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > - MPI_Aint is not sufficient for modern segmented addressing
> >>> (i.e.,
> >>> >> >> >> representing
> >>> >> >> >> > an address that may not be in main RAM and is not mapped in
> to
> >>> the
> >>> >> >> >> current
> >>> >> >> >> > process' linear address space)
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > If we no longer care about segmented addressing, that makes
> a
> >>> whole
> >>> >> >> >> bunch of
> >>> >> >> >> > BigCount stuff a LOT easier. E.g., MPI_Aint can basically
> be a
> >>> >> >> >> > non-segment-supporting address integer. AINT_DIFF and
> AINT_SUM
> >>> can
> >>> >> go
> >>> >> >> >> away,
> >>> >> >> >> > too.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > On Oct 24, 2019, at 5:35 PM, Jeff Hammond via
> >>> mpiwg-large-counts <
> >>> >> [
> >>> >> >> >> > mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ] > wrote:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Rolf:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Before anybody spends any time analyzing how we handle
> >>> segmented
> >>> >> >> >> addressing, I
> >>> >> >> >> > want you to provide an example of a platform where this is
> >>> >> relevant.
> >>> >> >> What
> >>> >> >> >> > system can you boot today that needs this and what MPI
> >>> libraries
> >>> >> have
> >>> >> >> >> expressed
> >>> >> >> >> > an interest in supporting it?
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > For anyone who didn't hear, ISO C and C++ have finally
> >>> committed to
> >>> >> >> >> > twos-complement integers ( [
> >>> >> >> >> >
> >>> >>
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r1.html
> >>> >> >> |
> >>> >> >> >> >
> >>> >>
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r1.html
> >>> >> >> ]
> >>> >> >> >> , [
> >>> >> >> >> > http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2218.htm |
> >>> >> >> >> > http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2218.htm
> ] )
> >>> >> because
> >>> >> >> >> modern
> >>> >> >> >> > programmers should not be limited by hardware designs from
> the
> >>> >> 1960s.
> >>> >> >> We
> >>> >> >> >> should
> >>> >> >> >> > similarly not waste our time on obsolete features like
> >>> >> segmentation.
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jeff
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > On Thu, Oct 24, 2019 at 10:13 AM Rolf Rabenseifner via
> >>> >> >> >> mpiwg-large-counts < [
> >>> >> >> >> > mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ] > wrote:
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >> I think that changes the conversation entirely, right?
> >>> >> >> >> >
> >>> >> >> >> > Not the first part, the state-of-current-MPI.
> >>> >> >> >> >
> >>> >> >> >> > It may change something for the future, or a new interface
> may
> >>> be
> >>> >> >> needed.
> >>> >> >> >> >
> >>> >> >> >> > Please, can you describe how MPI_Get_address can work with
> the
> >>> >> >> >> > different variables from different memory segments.
> >>> >> >> >> >
> >>> >> >> >> > Or whether a completely new function or a set of functions
> is
> >>> >> needed.
> >>> >> >> >> >
> >>> >> >> >> > If we can still express variables from all memory segments
> as
> >>> >> >> >> > input to MPI_Get_address, there may be still a way to
> flatten
> >>> >> >> >> > the result of some internal address-iquiry into a flattened
> >>> >> >> >> > signed integer with the same behavior as MPI_Aint today.
> >>> >> >> >> >
> >>> >> >> >> > If this is impossible, then new way of thinking and solution
> >>> >> >> >> > may be needed.
> >>> >> >> >> >
> >>> >> >> >> > I really want to see examples for all current stuff as you
> >>> >> >> >> > mentioned in your last email.
> >>> >> >> >> >
> >>> >> >> >> > Best regards
> >>> >> >> >> > Rolf
> >>> >> >> >> >
> >>> >> >> >> > ----- Original Message -----
> >>> >> >> >> >> From: "Jeff Squyres" < [ mailto:jsquyres at cisco.com |
> >>> >> >> jsquyres at cisco.com
> >>> >> >> >> ] >
> >>> >> >> >> >> To: "Rolf Rabenseifner" < [ mailto:rabenseifner at hlrs.de |
> >>> >> >> >> rabenseifner at hlrs.de ]
> >>> >> >> >> >> >
> >>> >> >> >> >> Cc: "mpiwg-large-counts" < [ mailto:
> >>> >> >> >> mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> >> mpiwg-large-counts at lists.mpi-forum.org ] >
> >>> >> >> >> >> Sent: Thursday, October 24, 2019 5:27:31 PM
> >>> >> >> >> >> Subject: Re: [Mpiwg-large-counts] Large Count - the
> >>> principles for
> >>> >> >> >> counts,
> >>> >> >> >> >> sizes, and byte and nonbyte displacements
> >>> >> >> >> >
> >>> >> >> >> >> On Oct 24, 2019, at 11:15 AM, Rolf Rabenseifner
> >>> >> >> >> >> < [ mailto:rabenseifner at hlrs.de | rabenseifner at hlrs.de ]
> >>> <mailto:
> >>> >> [
> >>> >> >> >> >> mailto:rabenseifner at hlrs.de | rabenseifner at hlrs.de ] >>
> >>> wrote:
> >>> >> >> >> >>
> >>> >> >> >> >> For me, it looked like that there was some misunderstanding
> >>> >> >> >> >> of the concept that absolute and relative addresses
> >>> >> >> >> >> and number of bytes that can be stored in MPI_Aint.
> >>> >> >> >> >>
> >>> >> >> >> >> ...with the caveat that MPI_Aint -- as it is right now --
> >>> does not
> >>> >> >> >> support
> >>> >> >> >> >> modern segmented memory systems (i.e., where you need more
> >>> than a
> >>> >> >> small
> >>> >> >> >> number
> >>> >> >> >> >> of bits to indicate the segment where the memory lives).
> >>> >> >> >> >>
> >>> >> >> >> >> I think that changes the conversation entirely, right?
> >>> >> >> >> >>
> >>> >> >> >> >> --
> >>> >> >> >> >> Jeff Squyres
> >>> >> >> >> >> [ mailto:jsquyres at cisco.com | jsquyres at cisco.com ]
> <mailto: [
> >>> >> >> >> >> mailto:jsquyres at cisco.com | jsquyres at cisco.com ] >
> >>> >> >> >> >
> >>> >> >> >> > --
> >>> >> >> >> > Dr. Rolf Rabenseifner . . . . . . . . . .. email [ mailto:
> >>> >> >> >> rabenseifner at hlrs.de |
> >>> >> >> >> > rabenseifner at hlrs.de ] .
> >>> >> >> >> > High Performance Computing Center (HLRS) . phone
> >>> >> ++49(0)711/685-65530
> >>> >> >> .
> >>> >> >> >> > University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
> >>> >> 685-65832
> >>> >> >> .
> >>> >> >> >> > Head of Dpmt Parallel Computing . . . [
> >>> >> >> >> http://www.hlrs.de/people/rabenseifner |
> >>> >> >> >> > www.hlrs.de/people/rabenseifner ] .
> >>> >> >> >> > Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office:
> Room
> >>> >> 1.307)
> >>> >> >> .
> >>> >> >> >> > _______________________________________________
> >>> >> >> >> > mpiwg-large-counts mailing list
> >>> >> >> >> > [ mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ]
> >>> >> >> >> > [
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
> >>> >> |
> >>> >> >> >> >
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts ]
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > --
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jeff Hammond
> >>> >> >> >> > [ mailto:jeff.science at gmail.com | jeff.science at gmail.com ]
> >>> >> >> >> > [ http://jeffhammond.github.io/ |
> >>> http://jeffhammond.github.io/ ]
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > _______________________________________________
> >>> >> >> >> > mpiwg-large-counts mailing list
> >>> >> >> >> > [ mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ]
> >>> >> >> >> > [
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
> >>> >> |
> >>> >> >> >> >
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts ]
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > --
> >>> >> >> >> > Jeff Squyres
> >>> >> >> >> > [ mailto:jsquyres at cisco.com | jsquyres at cisco.com ]
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > --
> >>> >> >> >> >
> >>> >> >> >> >
> >>> >> >> >> > Jeff Hammond
> >>> >> >> >> > [ mailto:jeff.science at gmail.com | jeff.science at gmail.com ]
> >>> >> >> >> > [ http://jeffhammond.github.io/ |
> >>> http://jeffhammond.github.io/ ]
> >>> >> >> >> > _______________________________________________
> >>> >> >> >> > mpiwg-large-counts mailing list
> >>> >> >> >> > [ mailto:mpiwg-large-counts at lists.mpi-forum.org |
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org ]
> >>> >> >> >> > [
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
> >>> >> |
> >>> >> >> >> >
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts ]
> >>> >> >> >> >
> >>> >> >> >> > _______________________________________________
> >>> >> >> >> > mpiwg-large-counts mailing list
> >>> >> >> >> > mpiwg-large-counts at lists.mpi-forum.org
> >>> >> >> >> >
> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
> >>> >> >> >>
> >>> >> >> >> --
> >>> >> >> >> Dr. Rolf Rabenseifner . . . . . . . . . .. email
> >>> >> rabenseifner at hlrs.de .
> >>> >> >> >> High Performance Computing Center (HLRS) . phone
> >>> >> ++49(0)711/685-65530 .
> >>> >> >> >> University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
> >>> >> 685-65832 .
> >>> >> >> >> Head of Dpmt Parallel Computing . . .
> >>> >> www.hlrs.de/people/rabenseifner .
> >>> >> >> >> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room
> >>> >> 1.307) .
> >>> >> >>
> >>> >> >> --
> >>> >> >> Dr. Rolf Rabenseifner . . . . . . . . . .. email
> >>> rabenseifner at hlrs.de .
> >>> >> >> High Performance Computing Center (HLRS) . phone
> >>> ++49(0)711/685-65530 .
> >>> >> >> University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
> >>> 685-65832 .
> >>> >> >> Head of Dpmt Parallel Computing . . .
> >>> www.hlrs.de/people/rabenseifner .
> >>> >> >> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room
> >>> 1.307) .
> >>> >>
> >>> >> --
> >>> >> Dr. Rolf Rabenseifner . . . . . . . . . .. email
> rabenseifner at hlrs.de
> >>> .
> >>> >> High Performance Computing Center (HLRS) . phone
> ++49(0)711/685-65530 .
> >>> >> University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
> 685-65832 .
> >>> >> Head of Dpmt Parallel Computing . . .
> www.hlrs.de/people/rabenseifner
> >>> .
> >>> >> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room
> 1.307) .
> >>>
> >>> --
> >>> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> .
> >>> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
> >>> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
> >>> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
> .
> >>> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .
> >>>
> >> _______________________________________________
> >> mpiwg-large-counts mailing list
> >> mpiwg-large-counts at lists.mpi-forum.org
> >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
> >>
> >
> >
> > --
> > Jeff Hammond
> > jeff.science at gmail.com
> > http://jeffhammond.github.io/
>
> --
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de .
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner .
> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .
>
>
>
--
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/
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