[petsc-dev] Building PETSc on LLNL Lassen

[Barry Smith]

> On Dec 14, 2020, at 2:35 AM, Stefano Zampini <stefano.zampini at gmail.com> wrote:
> 
> While we are discussing this dialect stuff, do we still want to test for gnu++{11|14} extensions before testing for c++{11|14} ? We get warnings when using KOKKOS since it replaces gnu++14 with c++14. What is the added value of using gnu++{11|14}?

   The code supposedly only tries the gnu++{11|14} if it thinks it is a GNU compiler. The thinking was that this is "broader" than c++14 and so most Gnu compiler users would want it by default.

    Since sticking to c++11/14  seems more popular today we could probably change the code to try the gnu++ variants only  if the user specifically asked.

   Barry

> 
> Il giorno lun 14 dic 2020 alle ore 08:21 Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>> ha scritto:
> 
>   So two configure sins. Setting values running configure without logging them into configure.log and setting values without testing them with configure tests :-)
> 
>   We need to finally deal properly with setting -cbin in configure; just defaulting causes all kinds of undebuggable problems. Why can't we also just set it to the C++ compiler? Is it because it cannot handle the MPI c++ compiler so it needs to be set to the underlying C++ compiler?
> 
>   Barry
> 
>   It is also strange that Jacob's configure.log seems to believe the IBM compiler is a GNU compiler (but because of poor logging configure does not log this information; fix coming in a MR soon).
> 
>> On Dec 13, 2020, at 6:32 PM, Junchao Zhang <junchao.zhang at gmail.com <mailto:junchao.zhang at gmail.com>> wrote:
>> 
>> Jacob,
>>   Do you need to add  'CUDAFLAGS=-ccbin xlc++' to specify the host compiler for CUDA? Note in cuda.py I added
>> 
>>     if self.compilers.cxxdialect in ['C++11','C++14']: #nvcc is a C++ compiler so it is always good to add -std=xxx. It is even crucial when using thrust complex (see MR 2822)
>>       self.setCompilers.CUDAFLAGS += ' -std=' + self.compilers.cxxdialect.lower()
>> 
>>  In your configure.log, there are 
>> #define PETSC_HAVE_CXX_DIALECT_CXX11 1
>> #define PETSC_HAVE_CXX_DIALECT_CXX14 1
>> 
>> I guess without -ccbin, nvcc uses gcc by default and your gcc does not support C++14.
>> 
>> --Junchao Zhang
>> 
>> 
>> On Sun, Dec 13, 2020 at 1:25 PM Jacob Faibussowitsch <jacob.fai at gmail.com <mailto:jacob.fai at gmail.com>> wrote:
>> Hello All,
>> 
>> Does anyone have any experience building petsc with cuda support on Lassen? I’ve been having trouble building with ibm xl compilers + spectrum-mpi + nvcc. NVCC seems to not like -std=c++14 argument, complaining that its configured host compiler doesn’t support it, but compiling the following “test.cc <http://test.cc/>":
>> 
>> #include <stdlib.h>
>> 
>> int main(int argc, char **argv)
>> {                                                                                                   
>>   int i = 1;
>>   i += argc;
>>   return(i);
>> }
>> 
>> With mpicc -std=c++14 test.cc <http://test.cc/> produces zero errors. 
>> ------------------------------------------------------------------------
>> 
>> Modules loaded:
>> 
>> module load xl/2020.11.12-cuda-11.1.1                                                               
>> module load spectrum-mpi
>> module load cuda/11.1.1
>> module load python/3.8.2
>> module load cmake
>> module load valgrind
>> module load lapack
>> 
>> My configure commands:
>> 
>> ./configure  --with-cc=mpicc --with-cxx=mpiCC --with-fc=mpifort --with-cuda --with-debugging=1 PETSC_ARCH=arch-linux-c-debug
>> 
>> The error:
>> 
>> TESTING: findMPIInc from config.packages.MPI(config/BuildSystem/config/packages/MPI.py:636)         *******************************************************************************
>>          UNABLE to CONFIGURE with GIVEN OPTIONS    (see configure.log for details):
>> -------------------------------------------------------------------------------
>> Bad compiler flag: -I/usr/tce/packages/spectrum-mpi/ibm/spectrum-mpi-rolling-release/include
>> *******************************************************************************
>> 
>> The actual configure.log error:
>> 
>> Executing: nvcc -c -o /var/tmp/petsc-2v0k4k61/config.setCompilers/conftest.o -I/var/tmp/petsc-2v0k4\
>> k61/config.setCompilers -I/var/tmp/petsc-2v0k4k61/config.types  -g -std=c++14 -I/usr/tce/packages/s\
>> pectrum-mpi/ibm/spectrum-mpi-rolling-release/include  -Wno-deprecated-gpu-targets /var/tmp/petsc-2v\
>> 0k4k61/config.setCompilers/conftest.cu <http://conftest.cu/> 
>> Possible ERROR while running compiler:
>> stderr:
>> nvcc warning : The -std=c++14 flag is not supported with the configured host compiler. Flag will be\
>>  ignored.
>> Source:
>> #include "confdefs.h"
>> #include "conffix.h"
>> 
>> int main() {
>> ;
>>   return 0;
>> }
>>                   Rejecting compiler flag -I/usr/tce/packages/spectrum-mpi/ibm/spectrum-mpi-rolling-release/include  due to 
>> nvcc warning : The -std=c++14 flag is not supported with the configured host compiler. Flag will be ignored.
>> 
>> 
>> Best regards,
>> 
>> Jacob Faibussowitsch
>> (Jacob Fai - booss - oh - vitch)
>> Cell: (312) 694-3391
> 
> 
> 
> -- 
> Stefano

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