Don’t know if this still applies, but here is what Jed said about this 10
months ago (https://gitlab.com/petsc/petsc/-/merge_requests/2466#note_275686270
<https://gitlab.com/petsc/petsc/-/merge_requests/2466#note_275686270>):
“A minor issue is that -ffp-contract=off is implied by -std=c*, versus
-ffp-contract=fast being default otherwise (with GCC).”
Thanks,
Pierre
> On 14 Dec 2020, at 9:35 AM, Stefano Zampini <stefano.zamp...@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}?
>
> Il giorno lun 14 dic 2020 alle ore 08:21 Barry Smith <bsm...@petsc.dev
> <mailto:bsm...@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.zh...@gmail.com
>> <mailto:junchao.zh...@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....@gmail.com
>> <mailto:jacob....@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
