[Bug fortran/34568] Inplace algorithm too slow when using array notation

[pault at gcc dot gnu dot org]

------- Comment #2 from pault at gcc dot gnu dot org  2008-01-02 16:15 -------
(In reply to comment #1)
Note that for last night's trunk, I get the following times
[EMAIL PROTECTED] tmp]# /irun/bin/gfortran -static pr34568.f90
[EMAIL PROTECTED] tmp]# ./a.out
   2.1826680    
   8.2267494    
[EMAIL PROTECTED] tmp]# /irun/bin/gfortran -static -O3 pr34568.f90
[EMAIL PROTECTED] tmp]# ./a.out
  0.39394000    
  0.83487302    

I did check that the scalarizer gives the correct result using:

PROGRAM INPLACE
        IMPLICIT NONE
        INTEGER, PARAMETER :: N = 8
        INTEGER, PARAMETER :: M = 1
        INTEGER            :: I, J
        REAL               :: ARR(N), ARR0(N) = (/1.,2.,3.,4.,5.,6.,7.,8./)
        REAL               :: T0, T1, T2
        CALL CPU_TIME(T0)
        arr = arr0
        DO I = 1, M
                ARR = ARR(N:1:-1)
        END DO
        print *, arr
        CALL CPU_TIME(T1)
        arr = arr0
        DO I = 1, M
                DO J = 1, N/2
                        ARR((/J,N-J+1/)) = ARR((/N-J+1,J/))
                END DO
        END DO
        print *, arr
        CALL CPU_TIME(T2)
        PRINT *, T1 - T0
        PRINT *, T2 - T1
END PROGRAM INPLACE

Note the error in your explicit case.

Paul


-- 

pault at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34568