compile speed

*To*: mathgroup at smc.vnet.net*Subject*: [mg74421] compile speed*From*: "Boson" <sandro.romani at gmail.com>*Date*: Wed, 21 Mar 2007 02:43:04 -0500 (EST)

dear mathematica users, i've written a simple function that works on a pair of binary matrices: (mathematica 5.2 linux, on a 32 bit platform) tab[nx_, ny_, frac_] := Table[If[Random[] < frac, 1, 0], {nx}, {ny}] nx = 25; ny = 50; frac1 = 0.1; frac2 = 0.5; p1 = 0.4; p2 = 0.2; tabrect = tab[nx, ny, frac1]; tabsq = tab[ny, ny, frac2]; testnocomp[mat1_, mat2_, n1_, n2_, pp1_, pp2_] := Module[{tmp, sum, val}, tmp = mat2; Do[sum = mat1[[k,j]] + mat2[[k,i]]; val = Which[sum == 2, If[Random[] < pp1, 1, tmp[[i,j]]], sum == 1, If[Random[] < pp2, 0, tmp[[i,j]]], sum == 0, tmp[[i,j]]]; tmp[[i,j]] = val, {k, n1}, {i, n2}, {j, n2}]; tmp]; Timing[resnc = testnocomp[tabrect, tabsq, nx, ny, p1, p2]; ] the result of the timing is {0.7558840000000013*Second, Null} since i need high values of nx,ny (~5000) and the loop scales as nx*ny^2, i tried to implement a compiled version of the previous function: test := Compile[{{mat1, _Integer, 2}, {mat2, _Integer, 2}, {n1, _Integer}, {n2, _Integer}, {pp1, _Real}, {pp2, _Real}}, Module[{tmp, sum, val}, tmp = mat2; Do[sum = mat1[[k,j]] + mat2[[k,i]]; val = Which[sum == 2, If[Random[] < pp1, 1, tmp[[i,j]]], sum == 1, If[Random[] < pp2, 0, tmp[[i,j]]], sum == 0, tmp[[i,j]]]; tmp[[i,j]] = val, {k, n1}, {i, n2}, {j, n2}]; tmp], {{Random[_], _Real}}]; Timing[res = test[tabrect, tabsq, nx, ny, p1, p2]; ] results are a disaster: {14.814747999999996*Second, Null} i'm sure this is related to my poor mathematica programming experience.. could you suggest me a faster version to solve this problem? regards, sandro