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fast summing alternative?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128332] fast summing alternative?
  • From: Chris <kristoph.steikert at gmail.com>
  • Date: Mon, 8 Oct 2012 02:28:43 -0400 (EDT)
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Dear all

The code below is part of a large compile function I wrote and the inputs, like the matrices weights and newData, are in fact large data files. Thus, I provide them in the following problem as random. Although, written as compile code (with CompilationTarget->"C") it is still too slow for the amounts of data I have to process. I provide two of my fastest alternatives, which sadly are not that fast. I do appreciate any help to make the code faster. Thanks in advance!


(*
What I do is simple: For each row of newMat and weights I construct a new row. The elements of this new row are the sums of the elements in weights if a certain requirement of the same element in newMat is met.
*)

Clear[bNum,nNum,weights,newMat,sortMat,tab];

bNum;
nNum=100;

weights=Table[RandomReal[{-10,10}],{b,1,bNum},{n,1,nNum}];
newMat=Table[RandomReal[{-10,10}],{b,1,bNum},{n,1,nNum}];
sortMat=Table[i,{i, -10, 10, 0.1}]; (*elements always evenly spaced*)

(*first alternative*)
tab=Table[
Sum[weights[[k,i]]*If[newMat[[k,i]] <= sortMat[[j]],1.,0.],{i,1,nNum}],{k,1,bNum},
{j,1,Length[sortMat]}];//AbsoluteTiming

(*second alternative*)
mat=Block[{k=1},
Reap[Do[
Sow[Table[Sum[weights[[k,i]]*If[newMat[[k,i]] <= sortMat[[j]],1.,0.],{i,1,nNum}],{j,1,Length[sortMat]}]];
k++,{bNum}]]][[2,1]];//AbsoluteTiming



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