Let’s compare two different vendors
This is the code: compute pi (It is not my code)
- Intel Core i5 10th gen, 16GB RAM.
- GNU Fortran (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0.
- ifort version 2021.1
$ caf -ffree-form -fcoarray=lib -O3 coarrays.f -o coarray_gfort $ ifort -free -coarray -O3 coarrays.f -o coarray_ifort
Run the program
Let’s run it several times to find out a patron (this is just one of many results)
$ time cafrun -np 8 ./coarray_gfort number of Fortran coarray images: 8 approximating pi in 2000000 steps. pi: 3.1415926535897931 iterated pi: 3.1395227456008259 pi error 0.207E-02 Elapsed wall clock time 0.475E-02 seconds, using 8 images. real 0m0,047s user 0m0,106s sys 0m0,096s
Intel Fortran results
$ time ./coarray_ifort number of Fortran coarray images: 8 approximating pi in 2000000 steps. pi: 3.14159265358979 iterated pi: 3.13952274560078 pi error 0.207E-02 Elapsed wall clock time 0.224E-02 seconds, using 8 images. real 0m0,081s user 0m0,166s sys 0m0,192s
Although elapsed time calculated by code is better with Intel Fortran, the operative system says the GFortran program ran faster. Is this ok for you? Am I doing something wrong? I am not able to interpret results.