1.4.8.1 dtime: Elapsed Time Since the Last dtime Call (Sun Studio 12: Fortran Library Reference)

Sun Studio 12: Fortran Library Reference

1.4.8.1 `dtime`: Elapsed Time Since the Last `dtime` Call

For dtime, the elapsed time is:

First call: elapsed time since start of execution
Subsequent calls: elapsed time since the last call to dtime
Single processor: time used by the CPU
Multiple Processor: the sum of times for all the CPUs, which is not useful data; use etime instead.

Note –
Calling dtime from within a parallelized loop gives non-deterministic results, since the elapsed time counter is global to all threads participating in the loop

The function is called by:

e = dtime( tarray )

tarray

real(2)

Output

e= -1.0: Error: tarray values are undefined

e≠ -1.0: User time in tarray(1) if no error. System time in tarray(2) if no error

Return value

real

Output

e= -1.0: Error

e≠ -1.0: The sum of tarray(1) and tarray(2)

Example: dtime(), single processor:

demo% cat tdtime.f
       real e, dtime, t(2)
       print *, ’elapsed:’, e, ’, user:’, t(1), ’, sys:’, t(2)
       do i = 1, 10000
        k=k+1
       end do
       e = dtime( t )
       print *, ’elapsed:’, e, ’, user:’, t(1), ’, sys:’, t(2)
       end
demo% f95 tdtime.f
demo% a.out
elapsed: 0.0E+0 , user: 0.0E+0 , sys: 0.0E+0
 elapsed: 0.03 , user: 0.01 , sys: 0.02
demo%