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Larry Ducie wrote:
...
I mean, when you sit down and explain to somebody WHY in some situations
using const is much more efficient than value you find it difficult when
you're not really sure why yourself.
Larry, a demonstration is even better than an explanation. Here's a
program that demonstrates the difference dramatically. The parameter
tells it how many times to loop doing the calls.
Call it with a parameter of 1000, then 10000, 100000 etc until it
registers a non-zero value for the CONST case.
I got these results:
CALL VALUECONST 100000
DSPLY value: 16 seconds | const: 0 seconds
CALL VALUECONST 1000000
DSPLY value: 169 seconds | const: 4 seconds
H dftactgrp(*no)
D byvalue pr
D bigparm 65535a varying value
D byconst pr
D bigparm 65535a varying const
D startTime s z
D endTime s z
D t1 s 5p 0
D t2 s 5p 0
D msg s 52a
D i s 10i 0
D valueconst pr extpgm('VALUECONST')
D ntimes 15p 5 const
D valueconst pi
D ntimes 15p 5 const
/free
startTime = %timestamp();
for i = 1 to %int(ntimes);
byvalue ('a');
endfor;
endTime = %timestamp();
t1 = %diff(endTime : startTime : *seconds);
startTime = %timestamp();
for i = 1 to %int(ntimes);
byconst ('a');
endfor;
endTime = %timestamp();
t2 = %diff(endTime : startTime : *seconds);
msg = 'value: ' + %editc(t1 : 'P') + ' seconds | '
+ 'const: ' + %editc(t2 : 'P') + ' seconds ';
dsply msg;
*inlr = '1';
/end-free
P byvalue b
D byvalue pi
D bigparm 65535a varying value
P byvalue e
P byconst b
D byconst pi
D bigparm 65535a varying const
P byconst e
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