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[Caml-list] OCaml Speed for Block Convolutions
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Date: 2001-06-07 (07:38)
From: William Chesters <williamc@p...>
Subject: Re: [Caml-list] OCaml Speed for Block Convolutions
Chris Hecker writes:
 > >My feeling has always been that the overhead of initialising a float
 > >array, per element, is considerably less than the cost of one floating
 > >point operation; so if you ever intend to actually use the array for
 > >anything, the inefficiency is negligible.
 > This is not true on modern processors, if I understand what you're saying.  Touching memory that's not in the cache is orders of magnitude slower than flops.  Even the best case, with the memory in the cache, touching memory is the same speed or slower than doing a flop on most CPUs.

Er, yes, you are right of course and "I didn't mean to say that" ;)
but rather: whatever you subsequently do to the float array, be it
arithmetic or churning it through the cache, is likely to be
more expensive per element than initialisation.


[head befuddled by day spent trying to trick C++ compiler into coding up
float array ops right, or that's my excuse!]
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