[Mpiwg-large-counts] Large Count - the principles for counts, sizes, and byte and nonbyte displacements
Rolf Rabenseifner
rabenseifner at hlrs.de
Fri Nov 1 03:00:26 CDT 2019
A small comment on the result of our telcon:
- Postfix _l for int -> MPI_Count
- Postfix _x for additionally
MPI_Aint -> MPI_Count
I.e., the additional routines in the derived datatype chapter.
Two of them already exist
MPI_Type_get_(true)extent_x
In Fortran we will have then for the
same routine two aliases:
- the overload one without _x
- and the explicit one with _x
For both ones, the internal function name is the same, with _x.
Best regards
Rolf
----- Jeff Hammond <jeff.science at gmail.com> wrote:
> 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/
--
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) .
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