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COBOL Performance Tuning


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jzhardy

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Joined: 31 Oct 2006
Posts: 87
Location: brisbane

PostPosted: Wed Dec 02, 2020 12:12 pm
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I have a requirement to write a security module for which I need to optimise for performance as far as possible.

some considerations:
- this will only ever run on Z/OS with COBOL 6.2 or higher
- compiler options will include ARCH(12)
- module will execute 10,000+ times per day
- within one transaction unit, module may be executed anywhere from 1 to 100 times

problem 1. How best to initialise a large array of primes.

I need to store the first 10,000 primes (>2) in an array structure (with binary usage). The following example demonstrates one way of doing this (cut down to the first four primes > 2)

Code:
01 PRIME-NOS PIC X(32) VALUE X'0000000300000005000000070000000B'.
01 FILLER REDEFINES PRIME-NOS OCCURS 4 TIMES.
   05 PRIME-NO PIC 99999 USAGE BINARY.


which seems to work fine, but it suffers somewhat from readability.

is there a better way to present this without compromising performance ? Any compiler directive that might do some of the heavy lifting ?



problem 2. fastest way to unpack a numeric.

I need a fast way to unpack a numeric, for it to be used in a dot product such as :

eg : 7234567 ==> (7,2,3,4,5,6,7) . (n1, n2, n3 .. n7) = 7n1 + 2n2 + ... + 7n7

I could either do something like :

Code:
   05 ws-input-digits pic 9(16).
   05 ws-input-digit  redefines ws-input-digits occurs 16 times pic 9.



... or copy to BCD, and then unpack. Which would be more efficient ?

input could be up to PIC 9(16), and could be within an array structure.
as in problem 1, I want the individual digits to have binary usage.


any other tips that can help appreciated. Also, do i need to do anything to exploit ZIIP processing ?
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prino
Warnings : 1

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Joined: 07 Feb 2009
Posts: 1238
Location: Vilnius, Lithuania

PostPosted: Wed Dec 02, 2020 7:20 pm
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You don't write security modules, you use commercial ones that have been thoroughly tested and use approved security standards.

Period. Full stop. End of story!
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steve-myers

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Joined: 30 Nov 2013
Posts: 869
Location: The Universe

PostPosted: Wed Dec 02, 2020 10:22 pm
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prino is 100% correct. Security is awfully difficult.

As for primes. Prepare your list and read them in as required rather than prepare a new list every time. It might not be "faster" in elapsed time, but it will certainly be "faster" in CPU time.

As for preparing a list. A technique called the Sieve of Eratosthenes is the best known, though probably not the fastest. Heck, I did that in the 1960s.

Good luck.
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Robert Sample

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Joined: 06 Jun 2008
Posts: 8569
Location: Dubuque, Iowa, USA

PostPosted: Thu Dec 03, 2020 10:36 pm
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Quote:
Also, do i need to do anything to exploit ZIIP processing ?
zIIP processors are for DB2 and Java work, primarily. Certain other workloads will also run on a zIIP, but you generally cannot do anything specifically to exploit the zIIP engine. Nothing you've posted indicates that you're doing anything that could run on a zIIP engine. The work that can run on a zIIP engine will usually run there automatically (even in DB2, not all work is zIIP-eligible).
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enrico-sorichetti

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Joined: 14 Mar 2007
Posts: 10712
Location: italy

PostPosted: Fri Dec 04, 2020 12:10 am
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Quote:
As for preparing a list. A technique called the Sieve of Eratosthenes is the best known, though probably not the fastest. Heck, I did that in the 1960s.


no reason to waste time coding,
lists for special numbers are available and can be downloaded

just the first link returned googling with "list of primes"

https://primes.utm.edu/lists/small/10000.txt
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enrico-sorichetti

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Joined: 14 Mar 2007
Posts: 10712
Location: italy

PostPosted: Fri Dec 04, 2020 12:15 am
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as usual people just focus on the lowly technical details

cryptography, security and friends is/are not just code,

there are implications for the organisation, auditing, training, ... ...
but above all legal and certification considerations

and I would never trust an algorithm developed using free forum consultancy icon_cool.gif
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jzhardy

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Joined: 31 Oct 2006
Posts: 87
Location: brisbane

PostPosted: Fri Dec 04, 2020 10:10 am
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agree with what's been posted above.

for the record, I've finished coding what I was asked to code, and have suggested to the business sponsor that they consider this piece of work as a POC (proof of concept), rather than something that should be moved into production.

By no means a wasted exercise : It's not often I get to combine my passion for number theory with programming.
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