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Using and Porting GNU Fortran

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8.11.9.242 System_Clock Intrinsic

 
CALL System_Clock(Count, Rate, Max)

Count: INTEGER(KIND=1); scalar; INTENT(OUT).

Rate: INTEGER(KIND=1); OPTIONAL; scalar; INTENT(OUT).

Max: INTEGER(KIND=1); OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: f90.

Description:

Returns in Count the current value of the system clock; this is the value returned by the UNIX function times(2) in this implementation, but isn't in general. Rate is the number of clock ticks per second and Max is the maximum value this can take, which isn't very useful in this implementation since it's just the maximum C unsigned int value.

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.


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