[Bug fortran/82471] do concurrent is much slower the ordinary do!

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82471

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |tkoenig at gcc dot gnu.org

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
There is a subtle problem with your test case, it is the
ordering of the variables in the DO concurrent statement.


  DO CONCURRENT( K=1:N, J=1:M, I=1:L)
     C(I,J,K) = A(I,J,K) + B(I,J,K)
  END DO

This is probably not what you meant to write; this
will fail (with the variable bounds you gave above in

  ALLOCATE( A(L,M,N), B(L,M,N), C(L,M,N) )

if any of L, M or N has a different value.

If you write

  DO CONCURRENT( I=1:L, K=1:N, J=1:M)

things are much faster.