There's another aspect to this, which is that for() loops in Perl
aren't so slow. IDL's interpreter is mired in molasses compared to
Perl's, so Perl loops don't impose quite the same performance hit as
IDL loops. (Of course, we all like PDL's threading engine much
better anyway... :-)
On Mar 1, 2007, at 3:45 PM, Karl Glazebrook wrote:
Either bad coding or some intrinsically unvectorisable.
These sort of slow downs are of order right in the situation where
you are stepping from an array pixel by pixel with a for() loop.
One comparison which would be useful of IDL vs PDL is how often you
need to resort to the for() loop, PDL I think has more language
tricks.
Karl
On 01/03/2007, at 6:38 PM, Frossie wrote:
Well, this is slighly anecdotal, but:
We have at least one experience of the same algorithm implemented in
IDL and in C, and the difference was significantly more than your
example (of the order of a minute v. an hour), though as we did not
implement the IDL version ourselves it could have been poor coding on
their part.
My point is that if you wanted to say something substantive you
should
try a range of algorithmic problems.
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