Timing runs for the last part of my previous post

*To*: mathgroup at smc.vnet.net*Subject*: [mg62082] Timing runs for the last part of my previous post*From*: "Matt" <anonmous69 at netscape.net>*Date*: Fri, 11 Nov 2005 02:51:46 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

OK, After I posted my earlier message (the one entitled "'Good' or 'Proper' Mathematica coding habits question"), I decided to try some timings for the last code sample I had a question on (the one trying to extract all sublists where each element of a sublist had to be negative). Here's what I found: This table was generated, then used for all the approaches: values = Table[{Random[Real, {-2, 2}] i, Random[Real, {-2, 2}] i}, {i, 1, 2000}]; Approach #1: ClearAll[testFuncOne]; testFuncOne[] := Module[{negElems = {}}, (If[Negative[#[[1]]] && Negative[#[[2]]], negElems = {negElems, #}]) & /@ values; StandardForm[Partition[Flatten[negElems], 2]]; ]; Approach #2: ClearAll[testFuncTwo]; testFuncTwo[] := Module[{negElems = {}}, Fold[If[Negative[#2[[1]]] && Negative[#2[[2]]], negElems = { negElems, #2}, negElems] &, values[[1]], values]; StandardForm[Partition[Flatten[negElems], 2]]; ]; Approach #3: ClearAll[testFuncThree]; testFuncThree[] := Module[{negElems = {} , lengthOfValues = Length[values], ii = 1}, While[ii = lengthOfValues, If[ Negative[values[[ii]][[1]]] && Negative[values[[ii]][[2]]], negElems = {negElems, values[[ii]]}; ] ii++; ]; StandardForm[Partition[Flatten[negElems], 2]]; ]; And the test run was: Timing[Do[testFuncOne[], {10^3}]][[1]] Timing[Do[testFuncTwo[], {10^3}]][[1]] Timing[Do[testFuncThree[], {10^3}]][[1]] The results obtained were 13.625, 12.812, and 19.11 Seconds. So, it appears that of the methods I tried, that Approach 2 is marginally better than Approach 1, and both Approach 1 and Approach 2 are better than Approach 3. Is it correct to assume from this that Fold will almost always be better than Map, given that other potential variants are kept similar? Or, because the difference is so small, that for most applications, I should go with whatever approach is quicker to 'code up'? Thanks, Matt