https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100855
Bug ID: 100855
Summary: pow run time gfortran vs ifort
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: nadavhalahmi560 at gmail dot com
Target Milestone: ---
I wrote the code below:
```
program power
implicit none
real :: sum, n, q
integer :: i, j
integer :: limit
real :: start, finish
sum = 0d0
limit = 10000
n = 2.0
q = 0.5
call CPU_TIME(start)
do j=1,limit
do i=1, limit
n = n*q
sum = sum + (i ** (0.05 + n))
end do
end do
call CPU_TIME(finish)
print *, sum
print '("Time = ",f6.3," seconds.")',finish-start
end program power
```
and compiled it using:
ifort pow.f90 -O3 -no-vec -o intel.out
gfortran pow.f90 -O3 -fno-tree-vectorize -o gnu.out
When I run `./intel.out` I get the following output:
3.3554432E+07
Time = 1.615 seconds.
When I run `./gnu.out` I get the following output:
33554432.0
Time = 7.817 seconds.
Therefore, gfortran is much slower than ifort. I get similar behavior for `log`
and `exp` functions.
gfortran -v:
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/software/x86_64/3.10.0/gcc/11.1.0/libexec/gcc/x86_64-pc-linux-gnu/11.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --prefix=/software/x86_64/3.10.0/gcc/11.1.0
--disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.1.0 (GCC)
ifort -v:
ifort version 19.1.3.304
