DTIME(VALUES, TIME)
initially returns the number of seconds of runtime since the start of the process's execution in TIME. VALUES returns the user and system components of this time in VALUES(1)
and VALUES(2)
respectively. TIME is equal to VALUES(1) +
VALUES(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 (wrap around) 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.
Please note, that this implementation is thread safe if used within OpenMP directives, i.e., its state will be consistent while called from multiple threads. However, if DTIME
is called from multiple threads, the result is still the time since the last invocation. This may not give the intended results. If possible, use CPU_TIME
instead.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
VALUES and TIME are INTENT(OUT)
and provide the following:
VALUES(1) : |
User time in seconds. | |
VALUES(2) : |
System time in seconds. | |
TIME : |
Run time since start in seconds. |
CALL DTIME(VALUES, TIME) . |
TIME = DTIME(VALUES) , (not recommended). |
VALUES | The type shall be REAL(4), DIMENSION(2) . |
TIME | The type shall be REAL(4) . |
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
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Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc-6.3.0/gfortran/DTIME.html