https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106565
--- Comment #2 from Quanhua Liu <quanhua.liu at noaa dot gov> ---
I modified the application code (see below) and use the "method" as a control
variable from command line.
I use the same code for both gfortran 10.3.0 and ifort 19.0.5.281
gfortran -O3 matrixCal.f90
time a.out 1
time a.out 2
ifort -O3 matrixCal.f90
time a.out 1
time a.out 2
where method 1, C = matmul(A, transpose(B) )
method 2, BB = transpose(B), C = matmul(A, BB)
The timing is given in the table below.
As you can see, using gfortran, method '2' is 6 times faster than the method
'1'.
Using ifort, method '2' is very similar to the method '1'. '1' is slightly fast
because '2' may copy B to BB.
Timing
compiler gfortran ifort
method 1 2 1 2
real 6.28 0.79 0.80 0.83
