Gcc openmp programming problem

Applications Programming
1

[solved]

Dear Linux users,
I'm a noob at openmp, gcc and c programming. I can run my own openmp code in terminal with no problem, eg. gcc -fopenmp program.c -o program.

But now I'm trying to compile and run another person's code, it contains a makefile and multiple .c and .h files. I don't know how to compile/run this?
Link to the files - https ://github.com/awreece/memory-bandwidth-demo

My attempt to make and run it:

linux@linux ~ $ make
gcc -O3 -march=native main.c monotonic_timer.c functions.c -o memory_profiler -fopenmp -DWITH_OPENMP

linux@linux ~ $ ./memory_profiler
           read_memory_rep_lodsq:  6.96 GiB/s
                read_memory_loop:  7.89 GiB/s
                 read_memory_sse:  7.79 GiB/s
               write_memory_loop:  6.58 GiB/s
          write_memory_rep_stosq:  7.28 GiB/s
                write_memory_sse:  6.61 GiB/s
    write_memory_nontemporal_sse:  5.86 GiB/s
             write_memory_memset:  6.64 GiB/s
memory_profiler: main.c:51: timeitp: Assertion `(1*(1024*1024*1024LL)) % omp_get_max_threads() == 0' failed.
Aborted

Program aborts half way when trying to run openmp code from main.c . I don't think I'm using openmp properly? How can I fix this?

Thankyou for your time,
pigeon

2

You're compiling it correctly.

How many cores does your system have? The failing assert amounts to, "your system must have a power-of-2 number of cores". So 1, 2, 4, 8, ... cores would be okay -- 6 cores would not.

I don't know very much about OMP at all. I'm not sure whether this is referring to physical cores or just the number OMP is allowed to use in this context.

8

Thanks for the reply. I needed to specify in the terminal how many cores I'm using. The code is now running properly :slight_smile: