Fortran

Misc

Change stack size

In Compaq Visual Fortran, go to Project Settings -> Win32 Release -> Link. In the Project Options text box, add something like /stack:0x989680 (the decimal value is 10000000 or 10MB).

Timing

system_clock tells the elapsed wall time between two successive calls.

integer(kind=8):: tclock1, tclock2, clock_rate
real(kind=8):: elapse_time

call system_clock(tclock1)

<code to be timed>

call system_clock(tclock2, clock_rate)
elapse_time = float(tclock2 - tclock1) / float(clock_rate)

cpu_time tells the CPU time used between two successive calls

real(kind=8):: t1, t2, elapsed_cpu_time
call cpu_time(t1)

<code to be timed>

call cpu_time(t2)
elapsed_cpu_time = t2 - t1

Since Unix provides a timing command called time, we can compare the system time and cpu time reported by Fortran's functions and Unix's time command; e.g. time ./a.out where a.out is the executable file written by a Fortran code. See an example from the High Performance Scientific Computing (University of Washington); the web lecture and the video lecture.