Article View: comp.lang.lisp.mcl
Article #602Re: map-array
From: Guillaume Cartier
Date: Fri, 11 Dec 1992 19:12
Date: Fri, 11 Dec 1992 19:12
27 lines
1601 bytes
1601 bytes
<--- | Based on the Code of Bill St.Clair for faster-climits I tried to write a | general map-array function, | both a mcl specific and a portable version. | | Then I compared this construct to mapc for sequences | | To my surprise, the mapping an array was slower than mapping over a list. | Am I missing something ? ---> Yes! It is true that access to a specific element of an array in generaly faster than access to a specific element of a list. But, in this case, we are not accessing elements individualy but mapping over the whole structure. Mapping over an array involves accessing every element individualy (each time having to do at least a multiplication and an addition) where as mapping over a list involves simple pointer indirections which are very fast. ********************************************************************* * Guillaume Cartier (514) 844-5294 (maison) * * L.A.C.I.M. (514) 987-4290 (bureau) * * Universite du Quebec a Montreal (514) 987-8477 (telecopieur) * * Montreal, Quebec, Canada cartier@math.uqam.ca (internet) * *********************************************************************
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Path: arc1-ca.pugleaf.net!sparky!uunet!stanford.edu!apple!cambridge.apple.com!cartier@math.uqam.ca From: cartier@math.uqam.ca (Guillaume Cartier) Newsgroups: comp.lang.lisp.mcl Subject: Re: map-array Message-ID: <9212111912.AA08784@mipsmath.math.uqam.ca> Date: 11 Dec 92 19:12:37 GMT Sender: info-mcl-request@cambridge.apple.com Lines: 27 Approved: comp.lang.lisp.mcl@Cambridge.Apple.C0M