That's Interesting Michael. Did you see any cases where the Cobol compiler generated unrolled loops of MVCs (like 4 each iteration)? I've seen that in cases with C/C++, but I don't remember the conditions. It's really wild how they do it as I recall. It may have to do with the settings of the compiler optimization options (size vs speed related).
Kirk Wolf Dovetailed Technologies https://coztoolkit.com On Thu, Oct 31, 2024, at 4:54 PM, Schmitt, Michael wrote: > That made me wonder: What does IBM think is the fasted move for various > lengths? > > Testing with IBM Enterprise COBOL for z/OS 6.2, compiled at OPT(2),ARCH(12) > on a z/14, moving from a fixed length field to a field of the same length and > can't be optimized away... > > - 1 to 4,096 bytes: generates a series of MVCs > - 4,097 to 77,824 bytes: generates an MVC loop, followed by one more if > needed > - 77,825 and up: generates an MVCL > > 77,824 is an odd number to break on. It is 19 * 4096. > > > If you're interested, the MVC loop for a length of 77,824 is: > > 000013 LA R2,152(,R9) # IN-W > 000013 LA R1,0(,R4) # OUT-W > 000013 LHI R0,0x12f > 000013 NOP > 000013 L0052: EQU * > 000013 MVC 0(256,R1),0(R2) # > 000013 LA R2,256(,R2) # > 000013 LA R1,256(,R1) # > 000013 BRCT R0,L0052 > 000013 MVC 0(256,R1),0(R2) # > > > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > Steve Thompson > Sent: Thursday, October 31, 2024 4:18 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Bounded string move? > > Uh, isn't that true up to about 1024 bytes (MVCs stacked)? And > then after the MVCL seems to be faster. > > I think I was at some disclosure meeting or SHARE when that was > said prior to 2010 (can't remember the exact year). > > I Remember that the MVCL is interruptible at end of a unit of > operation. > > This may have changed since the z/13s. > > Steve Thompson > > On 10/31/2024 4:18 PM, Charles Mills wrote: > > @Kirk: +1 > > > > @Shmuel: you know that an MVC loop is dramatically faster than MVCL? > > > > Surprising but true. > > > > CM > > > > On Wed, 30 Oct 2024 22:40:52 +0000, Seymour J Metz <sme...@gmu.edu> wrote: > > > >> I'm leaning towards SRST/MVCL. > >> > >> -- > >> Shmuel (Seymour J.) Metz > >> http://mason.gmu.edu/~smetz3 > >> עַם יִשְׂרָאֵל חַי > >> נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר > >> > >> > >> > >> ________________________________________ > >> From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf > >> of Kirk Wolf <k...@coztoolkit.com> > >> Sent: Wednesday, October 30, 2024 4:41 PM > >> To: IBM-MAIN@LISTSERV.UA.EDU > >> Subject: Re: Bounded string move? > >> > >> Caution: This email did not originate from George Mason’s mail system. Do > >> not click links or open attachments unless you recognize the sender and > >> know the content is safe. > >> > >> > >> It appears to me that your requirement matches the C function below. (?) > >> I would probably just use C/C++, but you can see what the IBM C/C++ > >> optimizing compiler generated. It seems unlikely to me that there is a > >> significantly better way. You might ask on mvs-asm370. > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
