[Openmp-dev] clang 9.0.0 + libstdc++ problem

[Gheorghe-Teod Bercea via Openmp-dev]

Hi Gabriele,

Did you set the CUDA_VISIBLE_DEVICES env var?
If not you should set it to: CUDA_VISIBLE_DEVICES=0,1,2,3

Which CUDA version are you using? Any mismatch between the version used to 
build Clang and the version used to compile/run the program will lead to 
such errors.

Are you compiling and running your program on the same machine where you 
built Clang?

When building Clang I see you have:

-DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_60

you should change that to:

-DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_70

for the V100 GPUs.

In addition you should also use this flag to build Clang:

-DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=70

Here you can specify several compute capabilities.

Thanks a lot,

--Doru






From:   "Jost, Gabriele (ARC-TNC)[Supersmith]" <gabriele.jost at nasa.gov>
To:     Gheorghe-Teod Bercea <Gheorghe-Teod.Bercea at ibm.com>
Cc:     "openmp-dev at lists.llvm.org" <openmp-dev at lists.llvm.org>
Date:   12/01/2019 04:42 PM
Subject:        Re: [EXTERNAL] Re:  [Openmp-dev] clang 9.0.0 + libstdc++ 
problem



Hi Doru and all,
I now have an install of clang + OpenMP target-offload using the old 
toolchain.
The benchmarks build, but when trying to run I get the following error:
 
pfe25.gjost 89> more  sp.A.out.txt
libomptarget fatal error 1: failure of target construct while offloading 
is mand
atory
 
I am using a Skylake node with 4 V100 GPUs, using only one of the GPUs. 
Would you have suggestions on how I can narrow down this issue? Should I 
rebuild libomp in debug mode?
Thanks in advance and best regards,
 
Gabriele Jost
 
************************************************************************
Gabriele Jost       NASA Ames Research Center
Email: Gabriele.Jost at nasa.gov      Mail Stop 258-6
Work Phone: (650) 604-0468         Bldg. 258, Rm. 232-4
Scientific & HPC Application           P.O. Box 1
Development/Optimization            Moffett Field, CA 94035-0001
************************************************************************
 
From: "Jost, Gabriele (ARC-TNC)[Supersmith]" <gabriele.jost at nasa.gov>
Date: Wednesday, November 27, 2019 at 1:08 PM
To: Gheorghe-Teod Bercea <Gheorghe-Teod.Bercea at ibm.com>
Cc: "openmp-dev at lists.llvm.org" <openmp-dev at lists.llvm.org>
Subject: Re: [EXTERNAL] Re: [Openmp-dev] clang 9.0.0 + libstdc++ problem
 
Thanks, Doru.
I have for now installed as below. I will try what you suggested next 
week!
 
 
Gabriele Jost
 
************************************************************************
Gabriele Jost       NASA Ames Research Center
Email: Gabriele.Jost at nasa.gov    Mail Stop 258-6
Work Phone: (650) 604-0468     Bldg. 258, Rm. 232-4
Scientific & HPC Application        P.O. Box 1
Development/Optimization         Moffett Field, CA 94035-0001
************************************************************************
 
From: Gheorghe-Teod Bercea <Gheorghe-Teod.Bercea at ibm.com>
Date: Wednesday, November 27, 2019 at 12:59 PM
To: "Jost, Gabriele (ARC-TNC)[Supersmith]" <gabriele.jost at nasa.gov>
Cc: "openmp-dev at lists.llvm.org" <openmp-dev at lists.llvm.org>
Subject: [EXTERNAL] Re: [Openmp-dev] clang 9.0.0 + libstdc++ problem
 
Hi Gabriele,

You can set the -DGCC_INSTALL_PREFIX to point to the folder with the 
desired version of GCC.

The GCC folder you want to point to is the one containing the lib and 
include folders. I use GCC 6.4.

Thanks a lot,

--Doru








From:        "Jost, Gabriele \(ARC-TNC\)\[Supersmith\] via Openmp-dev" 
<openmp-dev at lists.llvm.org>
To:        "openmp-dev at lists.llvm.org" <openmp-dev at lists.llvm.org>
Date:        11/27/2019 03:17 PM
Subject:        [EXTERNAL] [Openmp-dev] clang 9.0.0 + libstdc++ problem
Sent by:        "Openmp-dev" <openmp-dev-bounces at lists.llvm.org>

 
Hello llvm developers!
I am trying to build the OpenMP runtime with clang 9.0.0. The clang 
compiler fails to find the libstdc++ library.
I specified the pathname, but it does not help.
I had to resort to configuring like this:
cmake -DCMAKE_BUILD_TYPE=Release \
-DCMAKE_INSTALL_PREFIX="/nobackupnfs2/clang-install"\
-DCMAKE_C_COMPILER=/nobackupnfs2/clang-install/bin/clang\
-DCMAKE_CXX_COMPILER=/nobackupnfs2/clang-install/bin/clang++\
-DLIBOMPTARGET_DEP_LIBELF_LIBRARIES:FILEPATH=/usr/lib64/libelf.so.1 \
-DLLVM_LIBSTDCXX:FILEPATH=/usr/lib64/libstdc++.so.6\
-DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON\
-DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_60 \
-DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=35,60,70 ../llvm-9.0.0.src
 
Is there a way to tell clang to use the correct library? It complains that 
the library is too old, but I think it is because it does not find the 
right one.
 
Gabriele Jost
 
************************************************************************
Gabriele Jost       NASA Ames Research Center
Email: Gabriele.Jost at nasa.gov    Mail Stop 258-6
Work Phone: (650) 604-0468     Bldg. 258, Rm. 232-4
Scientific & HPC Application        P.O. Box 1
Development/Optimization         Moffett Field, CA 94035-0001
************************************************************************
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