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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: Language Efficiency
Date: 1995/04/06
Message-ID: <dewar.797198382@gnat>#1/1
X-Deja-AN: 100937921
references: <3lmt64$stt@dplanet.p2k.cbis.com> <3lrrqk$kbj@usenet.INS.CWRU.Edu>
 <1995Apr4.174002.9577@eisner.decus.org>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.c++,comp.lang.ada,comp.lang.cobol
Date: 1995-04-06T00:00:00+00:00
List-Id: <comp.lang.ada>

"Finally, let me note that the two specific examples given by Robert,
"code space" and "execution time" are often at odds with each other,
so a robust compiler will let the user indicate a preference."

yes, people often say this, but in my experience it is much less true
than people expect. The pragma Optimize (Space|Time) of Ada has very
seldom had much effect. 

Most modern highly optimizing compilers do NOT in fact have a selection
for time vs space. That's because in practice, reducing the number of
instructions reduces the execution speed on modern RISC machines.

Sure you can find examples, e.g. pulling things out of loops, where this
is theoretically the case, but I still think that in practice, over a big
chunk of code, there is not the kind of dichotomy that the quote above
suggests.