https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79930
--- Comment #6 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
Thanks Thomas, somehow I thought we would have built the temporary to do this.
(Well actully we do, but after the frontend passes)
Now we get:
$ gfc -O2 tp_array.f90
$ time ./a.out
This code variant uses intrinsic arrays to represent the contents of
Type(Vect3D).
Random Numbers, time: 43.6485367
Using SUM, time: 2.20666122
Using MATMUL (L), time: 1.58225632
Using MATMUL (R), time: 7.54129410
Where the LEFT case I did this:
type(Vect3D) pure function TP_LEFT(NU, D, NV) result(tensorproduct)
real(dp), intent(in) :: NU(4), NV(4)
real(dp) :: tmp(4)
type(Vect3D), intent(in) :: D(4,4)
tmp = matmul(NU, D%vec(1))
tensorproduct%vec(1) = dot_product(tmp, NV) ! "left"
tmp = matmul(NU, D%vec(2))
tensorproduct%vec(2) = dot_product(tmp, NV)
tmp = matmul(NU, D%vec(2))
tensorproduct%vec(3) = dot_product(tmp, NV) ! gives more expected results
end function
and just for grins:
$ gfc -Ofast -march=native -ftree-vectorize tp_array.f90
$ time ./a.out
This code variant uses intrinsic arrays to represent the contents of
Type(Vect3D).
Random Numbers, time: 42.7615433
Using SUM, time: 0.741546631
Using MATMUL (L), time: 0.522426605
Using MATMUL (R), time: 6.76409149
real 0m51.331s
user 0m50.389s
sys 0m0.501s
So we need to be careful how we use the tool to get the most out of the
optimizers.
