cpu_time

Date:

10-12-2011

NAME

CPU_TIME - Returns the processor time

SYNOPSIS

CALL CPU_TIME ([TIME=]time)
   REAL time

STANDARDS

Fortran

DESCRIPTION

The CPU_TIME intrinsic subroutine returns the user time if successful. This intrinsic subroutine accepts the following argument:

time

Must be a scalar and of type real. It is an output argument. The type of the argument is not restricted to any particular kind type.

The name of this intrinsic cannot be passed as an argument. The time returned by this intrinsic subroutine is user time on all systems.

A call to CPU_TIME must be done once and before the first timing loop to initialize the time structure. CPU_TIME includes time accumulated by the the current process.

RETURN VALUES

CPU_TIME yields -1.0 if the time cannot be returned.

EXAMPLES

The following program uses the CPU_TIME intrinsic subroutine:

PROGRAM CPUTIMETEST
     REAL RTIME(2)
     CHARACTER(LEN=400) :: EXPRIGHT2
     CHARACTER(LEN=800) :: EXPRIGHT
     INTEGER  :: J

     CALL CPU_TIME(RTIME(1))

     IF (RTIME(1) .EQ. -1.0) THEN
        PRINT *,'CPU_TIME NOT WORKING, QUIT'
        PRINT *,'RTIME(1) =',RTIME(1)
        STOP 'UNSUCCESSFUL'
     ENDIF

     CALL CPU_TIME(RTIME(1))
     DO J = 1, 400
        EXPRIGHT2(J:J) = " "
     ENDDO
     CALL CPU_TIME(RTIME(2))
     PRINT *,'ELAPSED CPUTIME TIME=',RTIME(2) - RTIME(1)
     CALL CPU_TIME(RTIME(1))
     DO J = 1, 800
        EXPRIGHT(J:J) = " "
     ENDDO
     CALL CPU_TIME(RTIME(2))
     PRINT *,'ELAPSED CPUTIME TIME=',RTIME(2) - RTIME(1)
END

This program generated the following output:

ELAPSED CPUTIME TIME= 7.61700000000004E-5
ELAPSED CPUTIME TIME= 7.722000000000284E-5