Dave,

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I’m acutely aware of that IBM advice, but in the last two decades I have also been involved in multiple rounds of “MIPS-saving” projects when management wanted application teams to “do more with less” (i.e. increase performance / reduce batch execution times without buying more/bigger hardware).

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The most effective solutions in those projects were finding the “CPU hot spots” (the Strobe product was always particularly effective for such efforts), and more times than not the worst “hot spots” turned out to be MVCL and sometimes CLCL instructions in compiler-generated COBOL code, and the second worst “hot spots” were the COBOL INITIALIZE verb for large heterogenous structures used inside of a loop, or at every invocation of a subroutine.

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Finding ways to hoist long-length moves/compares and INITIALIZE verbs out of business processing loops usually yielded the best/largest reductions of CPU and elapsed time used.? Second-best solutions were complicated and usually application-specific adjustments to business processing rules (along the lines of “the fastest I/O or business process is the one not done”).

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But I digress from the subject at hand.? You and Harold are right here, for Hercules fewer instructions will yield better performance, so if replacement of the C version of MEMSET would dramatically improve performance for C programs then the MVCL solution will probably work best under Hercules.

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Peter

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