COBOL "non-myth" confirmed - Index and subscripts (MF on Windows)
in [Cobol]
|
Prev: Help with Tcal
Next: COBOL Error Handling (was: What MF says about ROUNDED(was:Cobol Myth Busters
From: William M. Klein on 16 Sep 2007 02:01 "Robert" <no(a)e.mail> wrote in message news:rqnoe3hgjei5ir0b6ht4kefrmli2mr2cuq(a)4ax.com... > On Sat, 15 Sep 2007 11:43:24 -0700, Richard <riplin(a)Azonic.co.nz> wrote: <snip> > > The Micro Focus page is generalized advice. Write and tell them generalization > is BAD. > They shouldn't give advice until they test on every machine. Robert, You didn't originally CLAIM this(use index not subscript) was in any Micro Focus documentation. Do you now claim it is in the Micro Focus documentation and if so where? (Some - but not all - of your original comments WERE about MF documentation - and I would certainly say that some customer who has the relevant documentation and compiler should send in a comment complaining about it. It is worth noting that NONE of the "efficiency" recommendations from your original note were in the Net Express documentation. It - as far as I can tell - never comments on this topic.) P.S. IBM has some interesting documentation for their z/OS COBOL compiler. For example, http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/igy3pg32/8.1.3.1 talks about some of the table reference optimizaiton that the compiler does do (and therefore what types of code/structures they recommend using for optimal performancer). while http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/igy3pg32/8.1.3 does recommend the use of indexing over subscripts However, they also "back this up" with the performance statistics that support this, i.e. "using binary data items (COMP) to address a table is 30% slower than using indexes" -- Bill Klein wmklein <at> ix.netcom.com
From: Pete Dashwood on 16 Sep 2007 09:22 <docdwarf(a)panix.com> wrote in message news:fcht8h$cbo$1(a)reader1.panix.com... > In article <rqnoe3hgjei5ir0b6ht4kefrmli2mr2cuq(a)4ax.com>, > Robert <no(a)e.mail> wrote: >>On Sat, 15 Sep 2007 11:43:24 -0700, Richard <riplin(a)Azonic.co.nz> wrote: >> >>>On Sep 15, 6:50 pm, Robert <n...(a)e.mail> wrote: >>>> On Fri, 14 Sep 2007 22:51:45 -0700, Richard <rip...(a)Azonic.co.nz> >>>> wrote: > > [snip] > >>>> >Just why is 'index is faster than subscript' a myth, again ? >>>> >>>> 1. Because a timing test showed indexes are slower. >>> >>>And you have done a timing test on every machine in the universe. >> >>If humans were unable to generalize, there wouldn't be any machines. >>We'd be living in >>shacks and tents. > > What Mr Plinston puts forward, Mr Wagner, may demonstrate why there is a > season to things and a time to every purpose. The above might be phrased > otherwise and yet still retain some original flavor, eg: > > A: Just why is 'index is faster than subscript' a myth, again ? > > B: Because a timing test showed indexes are slower. > > A: '*A* timing test' (emphasis added) shows that under *a* set of > conditions one might not be better than the other; it is possible that > under other sets of conditions the other might be better than the one. > >> >>The Micro Focus page is generalized advice. Write and tell them >>generalization is BAD. > > Leaving aside the Brooklyn Bridge nature of this argument - 'Micro Focus > jumps off the Brooklyn Bridge, you will, too?' - one might believe that > when Micro Focus (or an appropriate representative thereof) comes > a-posting here the responses might be the same. > >>They shouldn't give advice until they test on every machine. > > It has been advised that one should tend to their own garden first, Mr > Wagner, before one tends to Micro Focus'... or something like that. > >> >>>> 2. Because multiplication is now as fast as loading an index. >>> >>>I didn't notice the elves coming in and doing that to my machine. >> >>You need to upgrade that '386. > > Only 486 and above are elf-compatible, sure! I'm fairy certain my core 2 duo is accommodating several billion pixies in it's HD1080 display memory. It's a gnome away from home. Pete. -- "I used to write COBOL...now I can do anything."
From: Robert on 16 Sep 2007 14:07 On Mon, 17 Sep 2007 01:17:37 +1200, "Pete Dashwood" <dashwood(a)removethis.enternet.co.nz> wrote: >(BTW, the reason I use indexes is not for any of the reasons you described; >I simply like INDEXED BY and SEARCH. Having gone to the trouble of defining >an index for a table it seems impolite to then use a subscript... :-)) >Couldn't care less whether they're faster or slower; on modern hardware it >makes very little difference, and even if it did, I'd still do it. Because I >can.:-)) I hope you use ODO on 'high speed' SEARCHes. If not, they're taking twice as long as they should for serial, 10% longer for binary.
From: Richard Brady on 16 Sep 2007 15:45 Pete Dashwood wrote: [snip] > D'jou think we might qualify that last to "Some of your claims..." or "Most > of your claims..." or specify "ALL" for North Americans who don't use > deductive logic? :-) > > Pete. This North American uses only inductive logic, if you please. Another Richard
From: Robert on 16 Sep 2007 17:43
On Sun, 16 Sep 2007 06:01:20 GMT, "William M. Klein" <wmklein(a)nospam.netcom.com> wrote: > >"Robert" <no(a)e.mail> wrote in message >news:rqnoe3hgjei5ir0b6ht4kefrmli2mr2cuq(a)4ax.com... >> On Sat, 15 Sep 2007 11:43:24 -0700, Richard <riplin(a)Azonic.co.nz> wrote: ><snip> >> >> The Micro Focus page is generalized advice. Write and tell them generalization >> is BAD. >> They shouldn't give advice until they test on every machine. > >Robert, > You didn't originally CLAIM this(use index not subscript) was in any Micro >Focus documentation. Do you now claim it is in the Micro Focus documentation >and if so where? Micro Focus does not say indexes are faster, in the efficiency tips nor elsewhere. Many Cobol programmers still believe it, because it was true in the Old Days. >(Some - but not all - of your original comments WERE about MF documentation - >and I would certainly say that some customer who has the relevant documentation >and compiler should send in a comment complaining about it. It is worth noting >that NONE of the "efficiency" recommendations from your original note were in >the Net Express documentation. It - as far as I can tell - never comments on >this topic.) Most of the recommendations are valid, at least on most platforms. I tested the ones that didn't sound right to me. >P.S. IBM has some interesting documentation for their z/OS COBOL compiler. For >example, > > http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/igy3pg32/8.1.3.1 > >talks about some of the table reference optimizaiton that the compiler does do >(and therefore what types of code/structures they recommend using for optimal >performancer). > > while > >http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/igy3pg32/8.1.3 > >does recommend the use of indexing over subscripts > >However, they also "back this up" with the performance statistics that support >this, i.e. > > "using binary data items (COMP) to address a table is 30% slower than using >indexes" Relative speeds are changing. Subscripting was about 500% slower in the Old Days. I don't doubt it WAS 30% slower when the above was written. My point is that subscripts are not slower on modern machines. |