SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
remain clear of any explicit statements which might obscure the logic of the model. A statement of
the form:
tally compute list of name
performs computations similar to those of the compute statement, but in a global manner, over
time, rather than locally to an instance of its use. Each time the named variable changes value, appropriate
actions are taken to collect the statistics requested in the compute list. Name may be the
name of an unsubscripted global variable, unsubscripted system attribute, or an attribute of a temporary,
permanent, or permanent compound entity. If name is an attribute of a permanent entity, as
many variables are reserved to store the statistical counters as there are elements of name. If name
is an attribute of a temporary entity, each entity record is generated with statistical counter-variable
attributes. Name cannot be a function attribute, a random variable, or a dimensioned array.
Some examples illustrate the use of the tally statement and the attributes and functions generated
by it.
1. Use of tally with an unsubscripted global variable:
Preamble:
preamble
define TIME as a real variable
.
.
tally MEAN.TIME as the mean,
and VAR.TIME as the variance of TIME
.
.
Preamble generates:
(a) A statistics-gathering function routine, which is called whenever an assignment is
made to TIME anywhere in the program. The function counts the number of times
TIME changes value, and records the sum and sum of squares of the values of TIME.
(b) Global variables [A.1, A.2, A.3] to record the number, sum, and
sum.of.squares of TIME for the computations of mean and variance.
(c) Functions MEAN.TIME and VAR.TIME which use the values of the global counters
to compute mean and variance whenever they are referenced.
The tally variables may be used in statements such as:
print 1 line with MEAN.TIME AND VAR.TIME as follows
MEAN = **.*** VARIANCE = ***.***
if (VAR.TIME/MEAN.TIME) le TOLERANCE
.
.
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