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8.47 DTIME — Execution time subroutine (or function)

DTIME(TARRAY, RESULT) initially returns the number of seconds of runtime since the start of the process's execution in RESULT. TARRAY returns the user and system components of this time in TARRAY(1) and TARRAY(2) respectively. RESULT is equal to TARRAY(1) + TARRAY(2).

Subsequent invocations of DTIME return values accumulated since the previous invocation.

On some systems, the underlying timings are represented using types with sufficiently small limits that overflows (wraparounds) are possible, such as 32-bit types. Therefore, the values returned by this intrinsic might be, or become, negative, or numerically less than previous values, during a single run of the compiled program.

If DTIME is invoked as a function, it can not be invoked as a subroutine, and vice versa.

TARRAY and RESULT are INTENT(OUT) and provide the following:

TARRAY(1): User time in seconds.
TARRAY(2): System time in seconds.
RESULT: Run time since start in seconds.


RESULT = DTIME(TARRAY), (not recommended).


TARRAYThe type shall be REAL, DIMENSION(2).
RESULTThe type shall be REAL.

Return value:
Elapsed time in seconds since the start of program execution.
          program test_dtime
              integer(8) :: i, j
              real, dimension(2) :: tarray
              real :: result
              call dtime(tarray, result)
              print *, result
              print *, tarray(1)
              print *, tarray(2)
              do i=1,100000000    ! Just a delay
                  j = i * i - i
              end do
              call dtime(tarray, result)
              print *, result
              print *, tarray(1)
              print *, tarray(2)
          end program test_dtime