Re: Using PL/I efficiently (++ robin)
9 Aug 1996 14:11:58 -0400

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From: (++ robin)
Newsgroups: comp.lang.pl1,comp.compilers
Date: 9 Aug 1996 14:11:58 -0400
Organization: Comp Sci, RMIT, Melbourne, Australia
Expires: 1 November 1996 00:00:00 GMT
References: 96-07-041 96-07-056 96-07-064 96-07-079 96-07-100 <96-07-123
Keywords: PL/I, performance

    >(Declaring a bit string ALIGNED meant operations on it were done inline
    >instead of by subroutine call -- about a 15-1 performance improvement as I

    >Not particularly interesting, until we started considering that during IBM's
    >compiler development -- all of alpha testing -- all of beta testing -- and
    >*a year of release* -- no one had considered it worth while to declare any
    >bit strings ALIGNED.

---Not entirely surprising. Another common one is to
specify full optimization OPTIMIZE(TIME), but to omit
to specify REORDER for the program.

---Without REORDER specified, the compiler is not usually able
to perform best optimization, typically of the type where
code can be shifted outside loops!


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