This question touches a nerve. In my very first job in IT, I was tasked to (re)write a program that tabulated the contents of a large master file. The idea was to examine each record and record its 'type' in a table. This was 1978. I was fresh out of programming school. Sort of starry eyed, I guess.
I found a manual with instruction timings and settled on the this sequence to increment each bucket: L R1,COUNTER LA R1,1(,R1) ST R1,COUNTER I can tell you that the program ran like a bat out hell. I was an application programmer trainee who heard from the sysprog staff that they used my program to benchmark new hardware! After I had moved on to other opportunities, I reflected on a huge oversight. In 1980--before the advent of XA--this logic would fail utterly beyond 16M records in any bucket. I never heard what happened, but I came to believe that outright speed was the wrong metric. Be careful to set the right goal. . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 323-715-0595 Mobile 626-543-6132 Office ⇐=== NEW robin...@sce.com -----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Brian Chapman Sent: Monday, August 12, 2019 5:48 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: (External):Instruction speeds Hi everyone, I did some searching, but I didn't find anything that really discussed this on the topic that I'm interested. Is there anything published that compares the cycle times of the most used instructions? For example; moving an address between areas of storage. I would assume that executing a LOAD and STORE would be much quicker than executing a MVC. Or executing a LOAD ADDRESS to increment a register instead of ADD HALF WORD. Or does this really matter as much as ordering the instructions so they are optimized for the pipeline? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
