How to use runtime tracing in OpenMP LLVM?

Question

I want to enable runtime tracing and see the output. Something like the output of

KD_TRACE(10, ( buff, gtid, schedule, chunk, lb, ub, st ) );

in kmp_dispatch.cpp

Refer this https://elixir.bootlin.com/llvm/latest/source/openmp/runtime/src/kmp_dispatch.cpp#L624

So, far I have followed the following tutorial: https://passlab.github.io/CSE436536/Assignments/project_dev_setup.html But I am not able to see any output from the tracer.

Is there a particular file or something where the output is logged? Or it is logged in the terminal?

I am compiling the openMP program like this:

clang omp1.c -L/PATH/llvm_work/openmp/BUILD/runtime/src   -o omp1

ldd omp1

This is the output:

linux-vdso.so.1 (0x00007ffdae305000)

libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fca2f3bb000)

/lib64/ld-linux-x86-64.so.2 (0x00007fca2f7ac000)

I hope this is using the OpenMP I have build from source and not libomp.

omp1.c:

#include<stdio.h>
#include "omp.h"

int main()
{
    int i=0;
    #pragma omp parallel for schedule(static)
    for(i=0;i<1000;++i)
    {
        int x = 4+i;
    }
}

But when I am trying to run this program using the same command I am getting an error.

/tmp/omp2-d969a9.o: In function `main':

omp2.c:(.text+0x1c8): undefined reference to omp_set_num_threads

clang-11: error: linker command failed with exit code 1 (use -v to see invocation)

Can anyone help me with correctly compiling the openMP programs with the openMP code I have built from source and also in using tracer?

Thank you.

Alexey Bataev · Accepted Answer · 2020-03-13 22:03:33Z

3

You need to compile with -fopenmp flag. Also, you need to have the debug version of the runtime (built with debug info) + set the environment variable export KMP_DEBUG=511.

answered Mar 13, 2020 at 22:03

Alexey Bataev

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Comments

noma · Accepted Answer · 2020-03-13 18:42:49Z

2

+25

I think you have to tell the compiler, that you want to use OpenMP via -fopenmp:

clang -fopenmp omp1.c -L/PATH/llvm_work/openmp/BUILD/runtime/src -o omp1

answered Mar 13, 2020 at 18:42

noma

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