Hello George, thank you a lot!
Everything seems to work now! :) Best, Patrick On 02.02.2014, at 14:15, George Bosilca wrote: > Just go for the most trivial: > > MPI_Type_contiguous(sizeof(__float128), MPI_BYTE, &my__float128); > > A little bit more info about the optional quad-precision floating-point > format is available on Wikipedia > (https://en.wikipedia.org/wiki/Double-double_%28arithmetic%29#Double-double_arithmetic). > > George. > > > On Feb 2, 2014, at 13:41 , Patrick Boehl > <patrick.bo...@physik.uni-muenchen.de> wrote: > >> Hello Jeff, >> >> thank you a lot for your reply! >> >> On 01.02.2014, at 23:07, Jeff Hammond wrote: >> >>> See Section 5.9.5 of MPI-3 or the section named "User-Defined >>> Reduction Operations" but presumably numbered differently in older >>> copies of the MPI standard. >>> >>> An older but still relevant online reference is >>> http://www.mpi-forum.org/docs/mpi-2.2/mpi22-report/node107.htm >>> >> >> In this example they construct this "datatype" >> >> --------- >> typedef struct { >> double real,imag; >> } Complex >> --------- >> >> and later >> >> --------- >> MPI_Datatype ctype; >> /* explain to MPI how type Complex is defined >> */ >> MPI_Type_contiguous(2, MPI_DOUBLE, &ctype); >> --------- >> >> Do I understand correctly that I have to find out how __float128 is >> constructed internally and >> convert it to a form which is compatible with the standard MPI Datatypes? >> In an analogue way as they do in the example. Up to now, I only found out >> that __float128 should >> be somehow the sum of two doubles. >> >> Again, I am grateful for any help! >> >> Best regards, >> Patrick >> >> >> >> >>> On Sat, Feb 1, 2014 at 2:28 PM, Tim Prince <n...@aol.com> wrote: >>>> >>>> On 02/01/2014 12:42 PM, Patrick Boehl wrote: >>>>> >>>>> Hi all, >>>>> >>>>> I have a question on datatypes in openmpi: >>>>> >>>>> Is there an (easy?) way to use __float128 variables with openmpi? >>>>> >>>>> Specifically, functions like >>>>> >>>>> MPI_Allreduce >>>>> >>>>> seem to give weird results with __float128. >>>>> >>>>> Essentially all I found was >>>>> >>>>> http://beige.ucs.indiana.edu/I590/node100.html >>>>> >>>>> where they state >>>>> ---- >>>>> MPI_LONG_DOUBLE >>>>> This is a quadruple precision, 128-bit long floating point number. >>>>> ---- >>>>> >>>>> But as far as I have seen, MPI_LONG_DOUBLE is only used for long doubles. >>>>> >>>>> The Open MPI Version is 1.6.3 and gcc is 4.7.3 on a x86_64 machine. >>>>> >>>> It seems unlikely that 10 year old course notes on an unspecified MPI >>>> implementation (hinted to be IBM power3) would deal with specific details >>>> of >>>> openmpi on a different architecture. >>>> Where openmpi refers to "portable C types" I would take long double to be >>>> the 80-bit hardware format you would have in a standard build of gcc for >>>> x86_64. You should be able to gain some insight by examining your openmpi >>>> build logs to see if it builds for both __float80 and __float128 (or >>>> neither). gfortran has a 128-bit data type (software floating point >>>> real(16), corresponding to __float128); you should be able to see in the >>>> build logs whether that data type was used. >>>> >>>> >>>> _______________________________________________ >>>> users mailing list >>>> us...@open-mpi.org >>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>> >>> >>> >>> -- >>> Jeff Hammond >>> jeff.scie...@gmail.com >>> _______________________________________________ >>> users mailing list >>> us...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users
