RE: what is unclear - LEAVE

[Vernon Hamberg <hambergv@xxxxxxxxxxxxxx>]

Brad

-snip-

Opinions, history, etc., are interesting, but can we get some facts? I
think I'll go generate an IR (intermediate representation). Actually, that
might be interesting and even helpful. <bg>

===================================================================

Adding to the previous post:

I created some little RPG III programs, basically as follows, and specified
GENOPT(*LIST), which puts the resulting MI into the source listing.

    READ      (executed only once, so I include in inside read)
    DOW       (adds to size of program)  
    READ      17 MI instruction / loop
    ENDDO     118 bytes

    DOU       18 MI instruction / loop
    READ      128 bytes
    IF
    LEAVE
    ENDIF
    ENDDO

    DO        16 MI instruction / loop
    READ      118 bytes
    IFEQ
    LEAVE
    ENDIF
    ENDDO

It looks like the last one is, in fact, the most efficient. However,
looking at the IR, it seems that the first 2 stay in the loop and the last
one does not. In fact, I just ran it and that is exactly what happens—it
goes through the cycle for each read!

Definitely, number one has fewer operations and should be faster. I just
ran both over a file of about 9000 records, record length about 450. The
DOW took 4 seconds, the DOU 5 seconds. Convinces me!

HTH

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN  55401-2499
(612) 371-1111 x480


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