January 2018 - mpiwg-rma - mailman3.cels.anl.gov

Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by maik peterson 04 Jan '18

04 Jan '18

jeff, in mpi you can put in what you like, the result is always the same: unexpected fiddle-faddle. mp 2018-01-04 0:23 GMT+01:00 Jeff Hammond <jeff.science(a)gmail.com>: > > > On Wed, Jan 3, 2018 at 1:07 AM, Thomas Jahns <jahns(a)dkrz.de> wrote: > > > > On 01/02/18 20:52, Jeff Hammond wrote: > >> > >> If a user passes a (base,size) pair that corresponds to a range of > addresses that are not allocated and/or mapped, is that a correct MPI > program? > > > > > > Such a thing wouldn't be a valid object pointer in C/C++ or a variable > in Fortran, i.e. both languages prohibit this. > > Which of the following MPI_Win_create calls are not using a valid object > pointer according to ISO C and/or C++? > > char a = '\0'; > > int main() { > .. > char * x = malloc(1); > MPI_Win_create(x,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); > ... > MPI_Win_create(&a,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); > .. > foo(); // compiler cannot prove this function does not call > // mmap(0x10000, 1, PROT_READ|PROT_WRITE, > MAP_FIXED|MAP_ANONYMOUS, -1, 4096); > .. > MPI_Win_create(0x10000,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); > .. > } > > >> The only text I can find that implies that buffers passed to > MPI_Win_create have to be allocated is the following, assuming that one > interprets "existing memory" this way. > >> > >> "Each process specifies a window of existing memory that it exposes to > RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) > > > > > > Since MPI is a library standard I would still expect all the guarantees > of the language standards involved to hold and the above to only be an > additional clarification? > > It's only a clarification. However, I don't think it's a good idea for > the MPI standard to punt this off on ISO C, because not every > implementation of MPI is an ISO C language lawyer, and very few users are. > > >> The Fortran-specific text is similarly suggestive, but it only says > that a user can pass a simply contiguous array, not that such a thing is > required. > >> > >> "In Fortran, one can pass the first element of a memory region or a > whole array, which must be ‘simply contiguous’" > > > > > > That's most probably because of the Fortran storage association > "feature" which is more about how arrays were passed in pre-Fortran 90 > times, i.e. it's legal for a caller C to pass some array element A(i) to a > subprogram P accepting an array argument B(*) provided the effective size > (that is the indices of B used in P match to valid indices of A). > > The widespread use of MPI in the context of non-strict Fortran is a > particularly good reason to clarify this ourselves rather than rely on ISO > Fortran. As has been discussed many times in the passed, MPI relies on > extensions and/or implementation-specific behavior with Fortran through the > latest standard. Only with Fortran 2018 will this situation disappear. > > Jeff > > > Regards, Thomas > > -- > > Thomas Jahns > > HD(CP)^2 > > Abteilung Anwendungssoftware > > > > Deutsches Klimarechenzentrum GmbH > > Bundesstraße 45a • D-20146 Hamburg • Germany > > > > Phone: +49 40 460094-151 <+49%2040%20460094151> > > Fax: +49 40 460094-270 <+49%2040%20460094270> > > Email: Thomas Jahns <jahns(a)dkrz.de> > > URL: www.dkrz.de > > > > Geschäftsführer: Prof. Dr. Thomas Ludwig > > Sitz der Gesellschaft: Hamburg > > Amtsgericht Hamburg HRB 39784 > > > > > > _______________________________________________ > > mpiwg-rma mailing list > > mpiwg-rma(a)lists.mpi-forum.org > > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > > > > > -- > Jeff Hammond > jeff.science(a)gmail.com > http://jeffhammond.github.io/ > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma >

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Jeff Hammond 03 Jan '18

03 Jan '18

On Wed, Jan 3, 2018 at 1:07 AM, Thomas Jahns <jahns(a)dkrz.de> wrote: > > On 01/02/18 20:52, Jeff Hammond wrote: >> >> If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? > > > Such a thing wouldn't be a valid object pointer in C/C++ or a variable in Fortran, i.e. both languages prohibit this. Which of the following MPI_Win_create calls are not using a valid object pointer according to ISO C and/or C++? char a = '\0'; int main() { .. char * x = malloc(1); MPI_Win_create(x,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); ... MPI_Win_create(&a,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); .. foo(); // compiler cannot prove this function does not call // mmap(0x10000, 1, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_ANONYMOUS, -1, 4096); .. MPI_Win_create(0x10000,1000,1,MPI_INFO_NULL,MPI_COMM_WORLD,&win); .. } >> The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. >> >> "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) > > > Since MPI is a library standard I would still expect all the guarantees of the language standards involved to hold and the above to only be an additional clarification? It's only a clarification. However, I don't think it's a good idea for the MPI standard to punt this off on ISO C, because not every implementation of MPI is an ISO C language lawyer, and very few users are. >> The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. >> >> "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" > > > That's most probably because of the Fortran storage association "feature" which is more about how arrays were passed in pre-Fortran 90 times, i.e. it's legal for a caller C to pass some array element A(i) to a subprogram P accepting an array argument B(*) provided the effective size (that is the indices of B used in P match to valid indices of A). The widespread use of MPI in the context of non-strict Fortran is a particularly good reason to clarify this ourselves rather than rely on ISO Fortran. As has been discussed many times in the passed, MPI relies on extensions and/or implementation-specific behavior with Fortran through the latest standard. Only with Fortran 2018 will this situation disappear. Jeff > Regards, Thomas > -- > Thomas Jahns > HD(CP)^2 > Abteilung Anwendungssoftware > > Deutsches Klimarechenzentrum GmbH > Bundesstraße 45a • D-20146 Hamburg • Germany > > Phone: +49 40 460094-151 > Fax: +49 40 460094-270 > Email: Thomas Jahns <jahns(a)dkrz.de> > URL: www.dkrz.de > > Geschäftsführer: Prof. Dr. Thomas Ludwig > Sitz der Gesellschaft: Hamburg > Amtsgericht Hamburg HRB 39784 > > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma -- Jeff Hammond jeff.science(a)gmail.com http://jeffhammond.github.io/

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Thomas Jahns 03 Jan '18

03 Jan '18

On 01/02/18 20:52, Jeff Hammond wrote: > If a user passes a (base,size) pair that corresponds to a range of addresses > that are not allocated and/or mapped, is that a correct MPI program? Such a thing wouldn't be a valid object pointer in C/C++ or a variable in Fortran, i.e. both languages prohibit this. > The only text I can find that implies that buffers passed to MPI_Win_create have > to be allocated is the following, assuming that one interprets "existing memory" > this way. > > "Each process specifies a window of existing memory that it exposes to RMA > accesses by the processes in the group of comm." (MPI 3.1 11.2.1) Since MPI is a library standard I would still expect all the guarantees of the language standards involved to hold and the above to only be an additional clarification? > The Fortran-specific text is similarly suggestive, but it only says that a user > can pass a simply contiguous array, not that such a thing is required. > > "In Fortran, one can pass the first element of a memory region or a whole array, > which must be ‘simply contiguous’" That's most probably because of the Fortran storage association "feature" which is more about how arrays were passed in pre-Fortran 90 times, i.e. it's legal for a caller C to pass some array element A(i) to a subprogram P accepting an array argument B(*) provided the effective size (that is the indices of B used in P match to valid indices of A). Regards, Thomas -- Thomas Jahns HD(CP)^2 Abteilung Anwendungssoftware Deutsches Klimarechenzentrum GmbH Bundesstraße 45a • D-20146 Hamburg • Germany Phone: +49 40 460094-151 Fax: +49 40 460094-270 Email: Thomas Jahns <jahns(a)dkrz.de> URL: www.dkrz.de Geschäftsführer: Prof. Dr. Thomas Ludwig Sitz der Gesellschaft: Hamburg Amtsgericht Hamburg HRB 39784

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Jeff Hammond 02 Jan '18

02 Jan '18

I liked your text, which does not use an platform-oriented terms e.g. virtual memory language. Jeff On Tue, Jan 2, 2018 at 1:59 PM, William Gropp <wgropp(a)illinois.edu> wrote: > I see no harm in adding a clarification - not an errata, and not a change. > Is my text sufficiently precise, or is there better text that we could use? > > Bill > > William Gropp > Director and Chief Scientist, NCSA > Thomas M. Siebel Chair in Computer Science > University of Illinois Urbana-Champaign > > > > > > > On Jan 2, 2018, at 3:54 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: > > I agree with all of these comments, but a user is arguing that these > requirements are not clear from the text, e.g. because the meaning of > existence in "existing memory" is not defined. It seems that what is > obvious to us is not obvious to users. > > Jeff > > > On Tue, Jan 2, 2018 at 12:54 PM, William Gropp <wgropp(a)illinois.edu> > wrote: > >> Yes. The r and l values must remain valid until the free. >> >> Bill >> >> William Gropp >> Director and Chief Scientist, NCSA >> Thomas M. Siebel Chair in Computer Science >> University of Illinois Urbana-Champaign >> >> >> >> >> >> >> On Jan 2, 2018, at 2:52 PM, Nathan Hjelm <hjelmn(a)mac.com> wrote: >> >> I would expect that the intent is also that the memory should not be >> freed/unmapped before the matching call to MPI_Win_free() correct? >> >> -Nathan >> >> On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp(a)illinois.edu> wrote: >> >> It was certainly the intent that the memory be allocated. Specifically, >> if a is the pointer and the region is of length L, then (assuming char *a >> and ) a[0] … a[L-1] must be valid r and l values at the point of the call. >> >> Bill >> >> William Gropp >> Director and Chief Scientist, NCSA >> Thomas M. Siebel Chair in Computer Science >> University of Illinois Urbana-Champaign >> >> On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: >> If a user passes a (base,size) pair that corresponds to a range of >> addresses that are not allocated and/or mapped, is that a correct MPI >> program? >> >> The only text I can find that implies that buffers passed to >> MPI_Win_create have to be allocated is the following, assuming that one >> interprets "existing memory" this way. >> >> "Each process specifies a window of existing memory that it exposes to >> RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) >> >> The Fortran-specific text is similarly suggestive, but it only says that >> a user can pass a simply contiguous array, not that such a thing is >> required. >> >> "In Fortran, one can pass the first element of a memory region or a whole >> array, which must be ‘simply contiguous’" >> >> Thanks, >> >> Jeff >> >> -- >> Jeff Hammond >> jeff.science(a)gmail.com >> http://jeffhammond.github.io/ >> _______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma >> >> >> _______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma >> >> _______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma >> >> >> >> _______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma >> > > > > -- > Jeff Hammond > jeff.science(a)gmail.com > http://jeffhammond.github.io/ > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > > > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > -- Jeff Hammond jeff.science(a)gmail.com http://jeffhammond.github.io/

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by William Gropp 02 Jan '18

02 Jan '18

I see no harm in adding a clarification - not an errata, and not a change. Is my text sufficiently precise, or is there better text that we could use? Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign > On Jan 2, 2018, at 3:54 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: > > I agree with all of these comments, but a user is arguing that these requirements are not clear from the text, e.g. because the meaning of existence in "existing memory" is not defined. It seems that what is obvious to us is not obvious to users. > > Jeff > > > On Tue, Jan 2, 2018 at 12:54 PM, William Gropp <wgropp(a)illinois.edu <mailto:[email protected]>> wrote: > Yes. The r and l values must remain valid until the free. > > Bill > > William Gropp > Director and Chief Scientist, NCSA > Thomas M. Siebel Chair in Computer Science > University of Illinois Urbana-Champaign > > > > > > >> On Jan 2, 2018, at 2:52 PM, Nathan Hjelm <hjelmn(a)mac.com <mailto:[email protected]>> wrote: >> >> I would expect that the intent is also that the memory should not be freed/unmapped before the matching call to MPI_Win_free() correct? >> >> -Nathan >> >> On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp(a)illinois.edu <mailto:[email protected]>> wrote: >> >>> It was certainly the intent that the memory be allocated. Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. >>> >>> Bill >>> >>> William Gropp >>> Director and Chief Scientist, NCSA >>> Thomas M. Siebel Chair in Computer Science >>> University of Illinois Urbana-Champaign >>> >>>> On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com <mailto:[email protected]>> wrote: >>>> If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? >>>> >>>> The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. >>>> >>>> "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) >>>> >>>> The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. >>>> >>>> "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" >>>> >>>> Thanks, >>>> >>>> Jeff >>>> >>>> -- >>>> Jeff Hammond >>>> jeff.science(a)gmail.com <mailto:[email protected]> >>>> http://jeffhammond.github.io/ <http://jeffhammond.github.io/>_______________________________________________ >>>> mpiwg-rma mailing list >>>> mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> >>>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma> >>> _______________________________________________ >>> mpiwg-rma mailing list >>> mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma>_______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma> > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma> > > > > -- > Jeff Hammond > jeff.science(a)gmail.com <mailto:[email protected]> > http://jeffhammond.github.io/ <http://jeffhammond.github.io/>_______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Jeff Hammond 02 Jan '18

02 Jan '18

I agree with all of these comments, but a user is arguing that these requirements are not clear from the text, e.g. because the meaning of existence in "existing memory" is not defined. It seems that what is obvious to us is not obvious to users. Jeff On Tue, Jan 2, 2018 at 12:54 PM, William Gropp <wgropp(a)illinois.edu> wrote: > Yes. The r and l values must remain valid until the free. > > Bill > > William Gropp > Director and Chief Scientist, NCSA > Thomas M. Siebel Chair in Computer Science > University of Illinois Urbana-Champaign > > > > > > > On Jan 2, 2018, at 2:52 PM, Nathan Hjelm <hjelmn(a)mac.com> wrote: > > I would expect that the intent is also that the memory should not be > freed/unmapped before the matching call to MPI_Win_free() correct? > > -Nathan > > On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp(a)illinois.edu> wrote: > > It was certainly the intent that the memory be allocated. Specifically, > if a is the pointer and the region is of length L, then (assuming char *a > and ) a[0] … a[L-1] must be valid r and l values at the point of the call. > > Bill > > William Gropp > Director and Chief Scientist, NCSA > Thomas M. Siebel Chair in Computer Science > University of Illinois Urbana-Champaign > > On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: > If a user passes a (base,size) pair that corresponds to a range of > addresses that are not allocated and/or mapped, is that a correct MPI > program? > > The only text I can find that implies that buffers passed to > MPI_Win_create have to be allocated is the following, assuming that one > interprets "existing memory" this way. > > "Each process specifies a window of existing memory that it exposes to RMA > accesses by the processes in the group of comm." (MPI 3.1 11.2.1) > > The Fortran-specific text is similarly suggestive, but it only says that a > user can pass a simply contiguous array, not that such a thing is required. > > "In Fortran, one can pass the first element of a memory region or a whole > array, which must be ‘simply contiguous’" > > Thanks, > > Jeff > > -- > Jeff Hammond > jeff.science(a)gmail.com > http://jeffhammond.github.io/ > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > > > > _______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma > -- Jeff Hammond jeff.science(a)gmail.com http://jeffhammond.github.io/

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by William Gropp 02 Jan '18

02 Jan '18

Yes. The r and l values must remain valid until the free. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign > On Jan 2, 2018, at 2:52 PM, Nathan Hjelm <hjelmn(a)mac.com> wrote: > > I would expect that the intent is also that the memory should not be freed/unmapped before the matching call to MPI_Win_free() correct? > > -Nathan > > On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp(a)illinois.edu> wrote: > >> It was certainly the intent that the memory be allocated. Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. >> >> Bill >> >> William Gropp >> Director and Chief Scientist, NCSA >> Thomas M. Siebel Chair in Computer Science >> University of Illinois Urbana-Champaign >> >>> On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com <mailto:[email protected]>> wrote: >>> If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? >>> >>> The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. >>> >>> "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) >>> >>> The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. >>> >>> "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" >>> >>> Thanks, >>> >>> Jeff >>> >>> -- >>> Jeff Hammond >>> jeff.science(a)gmail.com <mailto:[email protected]> >>> http://jeffhammond.github.io/ <http://jeffhammond.github.io/>_______________________________________________ >>> mpiwg-rma mailing list >>> mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> >>> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma> >> _______________________________________________ >> mpiwg-rma mailing list >> mpiwg-rma(a)lists.mpi-forum.org <mailto:[email protected]> >> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma <https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma>_______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Nathan Hjelm 02 Jan '18

02 Jan '18

I would expect that the intent is also that the memory should not be freed/unmapped before the matching call to MPI_Win_free() correct? -Nathan On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp(a)illinois.edu> wrote: It was certainly the intent that the memory be allocated. Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" Thanks, Jeff -- Jeff Hammond jeff.science(a)gmail.com http://jeffhammond.github.io/ _______________________________________________ mpiwg-rma mailing list mpiwg-rma(a)lists.mpi-forum.org https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma _______________________________________________ mpiwg-rma mailing list mpiwg-rma(a)lists.mpi-forum.org https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by Underwood, Keith D 02 Jan '18

02 Jan '18

That limitation is why MPI_WIN_CREATE_DYNAMIC was created… From: mpiwg-rma [mailto:[email protected]] On Behalf Of William Gropp Sent: Tuesday, January 02, 2018 3:19 PM To: MPI WG Remote Memory Access working group <mpiwg-rma(a)lists.mpi-forum.org> Cc: MPI WG Remote Memory Access working group <mpiwg-rma(a)mpi-forum.org> Subject: Re: [mpiwg-rma] MPI_Win_create on unmapped memory? It was certainly the intent that the memory be allocated. Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com<mailto:[email protected]>> wrote: If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" Thanks, Jeff -- Jeff Hammond jeff.science(a)gmail.com<mailto:[email protected]> http://jeffhammond.github.io/ _______________________________________________ mpiwg-rma mailing list mpiwg-rma(a)lists.mpi-forum.org<mailto:[email protected]> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma

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Re: [mpiwg-rma] MPI_Win_create on unmapped memory?
by William Gropp 02 Jan '18

02 Jan '18

It was certainly the intent that the memory be allocated. Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign > On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science(a)gmail.com> wrote: > > If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? > > The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way. > > "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) > > The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. > > "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" > > Thanks, > > Jeff > > -- > Jeff Hammond > jeff.science(a)gmail.com <mailto:[email protected]> > http://jeffhammond.github.io/ <http://jeffhammond.github.io/>_______________________________________________ > mpiwg-rma mailing list > mpiwg-rma(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma

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