Whatever their timing formulas or model-dependant behavior, in the old days of non-pipelined or minimally-pipelined CPU engines you ran your batch application program once with the appropriate test data using the "production" load module on an unloaded or lightly loaded machine, then you ran it once more with the same test data using a changed version of the same load module on that same machine, and you could compare the timing of those two jobs to see if you had improved or worsened that program's performance characteristics. Two tests and done, and good enough for all but the most finicky measurements (or for ISV code, which had to run on many varying models -- they always had a tougher job measuring useful performance characteristics, BTDTGTTS).
Now you run each version multiple times (some say 10 or more, others say 5) and take an average of the numbers to make that same comparison or it's not good enough. But as I said previously, I know that's just the way it is now, so I live with it. It's just part of the job today. Peter -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Shmuel Metz (Seymour J.) Sent: Monday, July 15, 2013 3:02 PM To: [email protected] Subject: Re: Benchmark of Relative instructions vers Base+displacement ones In <985915eee6984740ae93f8495c624c6c2319af4...@jscpcwexmaa1.bsg.ad.adp.com>, on 07/15/2013 at 11:01 AM, "Farley, Peter x23353" said: >I remember when I first was disabused of the quaint notion that the >CPU performance of a batch z/OS application could be measured in a >deterministic manner, There's deterministic and there's usefully deterministic. Back when IBM was still publishing instruction timings, there was a progression to increasingly complex timing formulae. There was also the issue that the time ranking of two code sequences would vary by model. -- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
