Is Dalton 2015 32bit or 64 bit

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blueyangliu
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Is Dalton 2015 32bit or 64 bit

Post by blueyangliu » 07 Apr 2015, 03:05

Hello, All
I compiled openmpi-1.6.5 with 64bit by gcc-4.9.2. while it shown me.
"WARNING: Cannot determine whether MPI is built for 32bit integers"
"WARNING: mpi.mod compiled with different compiler, will use mpif.h instead
" Performing Test MPI_COMPILER_MATCHES - Failed"
"Performing Test MPI_ITYPE_MATCHES - Failed".
Did dalton 2015 just support 32bit? how to compile 64bit dalton2015? What is the difference of performance between 32bit and 64 bit?

Best regards

taylor
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Re: Is Dalton 2015 32bit or 64 bit

Post by taylor » 07 Apr 2015, 05:00

The diagnostic you see is (at least in my experience) invariably associated with an incompatibility between your OpenMPI build and your Dalton build. Although the C interface to OpenMPI has now been "universalized", in the sense that you can e.g. compile OpenMPI with gcc and then link against that build with codes compiled with icc, or vice versa, this is not true (despite claims from the OpenMPI developers) for the Fortran interface. The fundamental problem is that there is no standard for the format of a compiled module file in Fortran. ifort produces module files that are relatively large and contain binary data, gfortran produces relatively small compiled module files that are often simple text with a preface line.

What this means is that if you build OpenMPI with gcc, you will not be able to straightforwardly build Fortran code to link against it with anything except gfortran. You need to ensure that your mpif90 or mpif77, etc., all ultimately invoke gfortran. Mixing Intel Fortran and gfortran will not work.

Note that in the first instance what I say here has nothing to do with 32-bit vs 64-bit integers. The diagnostic you see is caused, I suspect, by an incompatibility between compilers/libraries (the "using mpif.h" is an absolute giveaway as to what is going on there). There should be no problem building Dalton for 64-bit integers if you need to, although I would question why you feel the need to? With 32-bit addressing you can access up to 2 "gigawords", that is, 16GB of memory: do you really have more than 16GB per core, assuming you are going to run one MPI task per core? While as I say Dalton should build using 64-bit integers, it is essential then to ensure that all of the rest of the software stack (such as OpenMPI) is also built for 64-bit integers, as well as ensuring that the same compilers are used throughout, as I mentioned above. It is also important to verify that, if you have built OpenMPI yourself, that you are invoking all the correct mpif90, mpicc, etc., compilers and libraries and are not picking up some pieces that you have built but other pieces already installed by default on your system.

Best regards
Pete

blueyangliu
Posts: 5
Joined: 06 Apr 2015, 14:56
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Country: China

Re: Is Dalton 2015 32bit or 64 bit

Post by blueyangliu » 07 Apr 2015, 07:42

Hi Pete,
Thanks a lot. The 32 bit is good enough for me.

Regards

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