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PL/I code tuning/Performance improvement

 
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Virendra Shambharkar

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Joined: 26 Aug 2015
Posts: 54
Location: India

PostPosted: Mon Dec 05, 2016 11:57 am    Post subject: PL/I code tuning/Performance improvement
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Hi,

I am looking for documents or pointers for PL/I code tuning/Performance improvement . Have look over the net but did not come across any explicit documents . Any pointers will be helpful.

Thanks in advance.
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Bill Woodger

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Joined: 09 Mar 2011
Posts: 7314

PostPosted: Mon Dec 05, 2016 12:05 pm    Post subject: Reply to: PL/I code tuning/Performance improvement
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What's your specific problem, and are you able to "profile" it to know where it is occuring?
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Nic Clouston

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Joined: 10 May 2007
Posts: 2020
Location: UK

PostPosted: Mon Dec 05, 2016 2:38 pm    Post subject:
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Use 'ALIGNED' and 'REORDER'. Make the most used code the targt if IF/THEN/ELSE e.g.
Code:
IF not an abort condition
THEN some code
ELSE abort


instead of
Code:
IF abort condition
THEN abort
ELSE some code


The same for SWITCH.

Avoid DATA CONVERSION WILL BE DONE BY SUB-ROUTINE CALL messages - move your data through the datatypes eg CHAR-> PIC -> FIXED DEC.

That is just some of the simpler things that should be done. There was an entire document on the subject from IBM - but it may have been Internal Use Only. I am no longer able to find my copy.
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Virendra Shambharkar

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Joined: 26 Aug 2015
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PostPosted: Mon Dec 05, 2016 3:10 pm    Post subject: Reply to: PL/I code tuning/Performance improvement
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Thanks a lot Nic.
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Nic Clouston

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Joined: 10 May 2007
Posts: 2020
Location: UK

PostPosted: Tue Dec 06, 2016 4:06 pm    Post subject:
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Some other bits:

Use LOCATE mode when reading/writing data sets
Use the TOTAL option when declaring files
Use as many buffers as you can for your data sets - avoiding disk access
Use FIXED BIN for counters
There is an entire chapter in the programming guide re performance.
Use PLIXOPT to find correct ISA size and then code it
Remove internal routines that are used only once
Remove repetetive, i.e. duplicate, tests
Limit data movement
Hard-code values - in particular parameters to BUILTIN functions
Call user exits directly
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