All sounds like good reasons to amend the Bull test suite to no longer check
for character and logical. :-)
> On Apr 15, 2016, at 5:38 PM, Larry Baker <ba...@usgs.gov> wrote:
>
> I also remember reading in the past about problems with C sizeof and
> multibyte characters. I just looked over the C90 standard. In C90 code, the
> sizeof operator returns size_t in bytes. Except that it always returns 1 for
> char, signed char, or unsigned char. For an array, C90 says sizeof returns
> the number of bytes. I interpret this to mean that when the execution
> character set is a 16-bit multibyte character set, sizeof a char is 1, while
> sizeof a char[1] is 2. I've never actually tested this.
>
> Any programs that marshall character strings for interchange have to be quite
> specific, I think, in the character set being exchanged. I don't think MPI
> SIZEOF has a way to know or specify the semantics of the character set.
>
> Larry Baker
> US Geological Survey
> 650-329-5608
> ba...@usgs.gov
>
>
>
> On 15 Apr 2016, at 2:23 PM, Larry Baker wrote:
>
>> Be careful what you wish for.
>>
>> I remember looking at this issue a while ago, but I can't remember why or
>> how I ran into it. I do remember convincing myself that the MPI standard
>> was correct in restricting SIZEOF to numeric types. For one thing, a
>> character variable type is a string container in Fortran, while in C it is a
>> single character. What would be the correct interpretation for SIZEOF in
>> Fortran? The maximum length? The TRIM'd length? What would be the correct
>> interpretation in C? 1? strlen()? strlen()+1? The size of a character
>> itself may not be the same on either end of an MPI connection if, for
>> example, one program is compiled using 8-bit characters and the other is
>> compiled using uses 16-bit characters. Interchanging strings opens up a can
>> of worms. As far as logical, there is no C logical type. In Fortran, while
>> the size of a logical variable is specified as a "storage unit" (the same as
>> an integer), the representation of true and false is unspecified, and, thus,
>> is processor dependent. On VAXes, only a single bit matters; the
>> instruction set supports this logical data type. (In C, thought there is no
>> logical data type, the C standard does specify 0=false and 1=true for the
>> result of relational and logical operators and 0=false and not 0=true for
>> logical operator operands.) This means it is problematic to exchange
>> logical data between Fortran programs (C makes no sense, since there is no
>> logical data type) when different compilers (part of what Fortran calls a
>> processor) are used.
>>
>> Better to find out what discussions took place in the MPI standards
>> committee before adding extensions to SIZEOF. They may very well have good
>> reasons to avoid character and logical data, as I concluded.
>>
>> Larry Baker
>> US Geological Survey
>> 650-329-5608
>> ba...@usgs.gov
>>
>>
>>
>> On 15 Apr 2016, at 5:34 AM, Jeff Squyres (jsquyres) wrote:
>>
>>> Nadia --
>>>
>>> I believe that the character and logical types are not in this script
>>> already because the description of MPI_SIZEOF in MPI-3.1 says that the
>>> input choice buffer parameter is:
>>>
>>> IN x a Fortran variable of numeric intrinsic type (choice)
>>>
>>> As I understand it (and my usual disclaimer here: I am *not* a Fortran
>>> expert), CHARACTER and LOGICAL types are not numeric in Fortran.
>>>
>>> However, we could add such interfaces as an extension.
>>>
>>> I just checked MPICH 3.2, and they *do* include MPI_SIZEOF interfaces for
>>> CHARACTER and LOGICAL, but they are missing many of the other MPI_SIZEOF
>>> interfaces that we have in OMPI. Meaning: OMPI and MPICH already diverge
>>> wildly on MPI_SIZEOF. :-\
>>>
>>> I guess I don't have a strong opinion here. If you file a PR for this
>>> patch, I won't object. :-)
>>>
>>>
>>>> On Apr 15, 2016, at 3:22 AM, DERBEY, NADIA <nadia.der...@atos.net> wrote:
>>>>
>>>> Hi,
>>>>
>>>> The following trivial example doesn't compile because of 2 missing types
>>>> in the MPI_SIZEOF subroutines (in mpi_sizeof.f90).
>>>>
>>>> [derbeyn@btp0 test]$ cat mpi_sizeof.f90
>>>> program main
>>>> ! use mpi
>>>> include 'mpif.h'
>>>>
>>>> integer ierr, sz, mpisize
>>>> real r1
>>>> integer i1
>>>> character ch1
>>>> logical l1
>>>>
>>>> call MPI_INIT(ierr)
>>>> call MPI_SIZEOF(r1, sz, ierr)
>>>> call MPI_SIZEOF(i1, sz, ierr)
>>>> call MPI_SIZEOF(l1, sz, ierr)
>>>> call MPI_SIZEOF(ch1, sz, ierr)
>>>> call MPI_FINALIZE(ierr)
>>>>
>>>> end
>>>> [derbeyn@btp0 test]$ mpif90 -o mpi_sizeof mpi_sizeof.f90
>>>> mpi_sizeof.f90(14): error #6285: There is no matching specific
>>>> subroutine for this generic subroutine call. [MPI_SIZEOF]
>>>> call MPI_SIZEOF(ch1, sz, ierr)
>>>> -------------^
>>>> mpi_sizeof.f90(15): error #6285: There is no matching specific
>>>> subroutine for this generic subroutine call. [MPI_SIZEOF]
>>>> call MPI_SIZEOF(l1, sz, ierr)
>>>> -------------^
>>>> compilation aborted for mpi_sizeof.f90 (code 1)
>>>>
>>>>
>>>> This problem happens both on master and v2.x. The following patch seems
>>>> to solve the issue:
>>>>
>>>> diff --git a/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
>>>> b/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
>>>> index 5ea3dca3..a2a99924 100755
>>>> --- a/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
>>>> +++ b/ompi/mpi/fortran/base/gen-mpi-sizeof.pl
>>>> @@ -145,6 +145,9 @@ sub generate {
>>>> # Main
>>>>
>>>> #############################################################################
>>>>
>>>> +queue_sub("character", "char", "character_kinds");
>>>> +queue_sub("logical", "logical", "logical_kinds");
>>>> +
>>>> for my $size (qw/8 16 32 64/) {
>>>> queue_sub("integer(int${size})", "int${size}", "int${size}");
>>>> }
>>>>
>>>> Regards,
>>>> Nadia
>>>>
>>>> --
>>>> Nadia Derbey - B1-387
>>>> HPC R&D - MPI
>>>> Tel: +33 4 76 29 77 62
>>>> nadia.der...@atos.net
>>>> 1 Rue de Provence BP 208
>>>> 38130 Echirolles Cedex, France
>>>> www.atos.com
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>>>> Link to this post:
>>>> http://www.open-mpi.org/community/lists/devel/2016/04/18765.php
>>>
>>>
>>> --
>>> Jeff Squyres
>>> jsquy...@cisco.com
>>> For corporate legal information go to:
>>> http://www.cisco.com/web/about/doing_business/legal/cri/
>>>
>>> _______________________________________________
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>>> Link to this post:
>>> http://www.open-mpi.org/community/lists/devel/2016/04/18766.php
>>
>
--
Jeff Squyres
jsquy...@cisco.com
For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/
