SIMSCRIPT II.5 Programming Language

Discrete Simulation Concepts
reset the daily totals of N.QUEUE
reset the weekly totals of N.QUEUE
or
reset the daily and weekly totals of N.QUEUE
If a reset statement does not specify one of the declared qualifying names, all counters associated
with the relevant variable are reinitialized. Where variables are used in histogram range specifications,
they should be only altered following a reset statement, and before any subsequent reference
to the monitored variable.
It should be noted that the compiler can only generate the necessary statistics-gathering logic in
those cases where values are referenced using their globally known names. If a variable is passed
to a routine as an argument, where it is referenced by another name, the appropriate actions cannot
be taken. If it is returned as a yielded argument, of course, the changes will be noted upon return
from the routine. An exception, however, is the case where an array base pointer is passed as an
argument. As such pointers effectively pass the array values by reference, the actual elements of a
monitored array may be referenced under a different name, that of the local argument of the called
routine. Such usage cannot be detected by the compiler and, hence, no statistics can be maintained
for these references.
A final note on statistics-gathering concerns the minimization of storage requirements for computations
of statistical quantities. It may happen that the statistics of changes to a program variable is
required, but the actual value of the variable is not needed for any other purpose. Consider the following
example:
preamble
.
.
temporary entities
every JOB belongs to a QUEUE,
has a DUE.DATE and an OVERRUN
.
.
tally AVG.LATE as the mean of OVERRUN
end
process JOB.STATS
.
.
for each JOB in QUEUE
let OVERRUN = DUE.DATE(JOB) - time.v
.
.
If the logic of the program does not require the value of OVERRUN for any other purpose than to
compute the average, it is possible to perform these tally computations on OVERRUN without its
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