SYSTEM_CLOCK(COUNT, COUNT_RATE, COUNT_MAX)

Purpose

Returns numeric data from a real-time clock.

Class

Subroutine

Argument type and attributes

COUNT (optional): An INTENT(OUT) INTEGER. The initial value of COUNT depends on the current value of the processor clock in a range from 0 to COUNT_MAX. COUNT increments by one for each clock count until it reaches the value of COUNT_MAX. At the next clock count after COUNT_MAX, the value of COUNT resets to zero.
COUNT_RATE (optional): An INTENT(OUT) INTEGER or REAL scalar. When using the default centisecond resolution, COUNT_RATE refers to the number of processor clock counts per second or to zero if there is no clock.; If you specify a microsecond resolution using –qsclk=micro, the value of COUNT_RATE is 1 000 000 clock counts per second.

COUNT_MAX (optional): An INTENT(OUT) INTEGER scalar. When using the default centisecond resolution, COUNT_MAX is the maximum number of clock counts for a given processor clock.; If you specify a microsecond resolution using -qsclk=micro and COUNT_MAX is of type INTEGER(4), the value of COUNT_MAX is 1 799 999 999 clock counts, or about 30 minutes.; If you specify a microsecond resolution using -qsclk=micro and COUNT_MAX is of type INTEGER(8), the value of COUNT_MAX is 86 399 999 999 clock counts, or about 24 hours.

Examples

IBM extension begins In the following example, the clock is a 24-hour clock. After the call to SYSTEM_CLOCK, the COUNT contains the day time expressed in clock ticks per second. The number of ticks per second is available in the COUNT_RATE. The COUNT_RATE value is implementation dependent.

     INTEGER, DIMENSION(8) :: IV
     TIME_SYNC: DO
     CALL DATE_AND_TIME(VALUES=IV)
     IHR  = IV(5)
     IMIN = IV(6)
     ISEC = IV(7)
     CALL SYSTEM_CLOCK(COUNT=IC, COUNT_RATE=IR, COUNT_MAX=IM)
     CALL DATE_AND_TIME(VALUES=IV)

     IF ((IHR == IV(5)) .AND. (IMIN == IV(6)) .AND. &
       (ISEC == IV(7))) EXIT TIME_SYNC

     END DO TIME_SYNC

     IDAY_SEC = 3600*IHR + IMIN*60 + ISEC
     IDAY_TICKS = IDAY_SEC * IR

     IF (IDAY_TICKS /= IC) THEN
       STOP 'clock error'
     ENDIF
     END

Related information

See the -qsclk compiler option in the XL Fortran Compiler Reference for more information on specifying system clock resolution.

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