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Coarrays from Fortran 2008/2018 are native Fortran high-level abstractions that are supported by a range of libraries, including OpenMPI. By using htop or other CPU monitor, you can see that multiple CPU cores are used.


Compute value of Pi iteratively:

cafrun coarray/coarray_pi

You can optionally specify the resolution of Pi, say 1e-8:

cafrun coarray/coarray_pi 1e-8

Comparing gfortran and ifort coarray performance (computation time in seconds on i7-4650, 4 threads). -O3 was used for both compilers. Notice that ifort is over 5x faster than gfortran.

YES this was using pi2008.f90 for both, to ensure that Fortran 2018 co_sum() didn't have a disadvantage over the explicit Fortran 2008 loop. The performance of co_sum was essentially the same in pi.f90 as in pi2008.f90.

dx gfortran 7.2.0 ifort 18.1
1e-7 0.254 0.049
1e-8 2.72 0.489
1e-9 26.0 4.88
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