Accelerating MATLAB Performance

263Implicit Parallelization (Vectorization and Indexing)

cellsize*ones(1,64/cellsize),...

cellsize*ones(1,64/cellsize));

end

r = p;

% Non-vectorized method

C1 = zeros(4,4,r,4,4,r);

for ir=1:4

for ic=1:4

for is=1:r

for jr=1:4

for jc=1:4

for js=1:r

temp = cellfun(@(x,y) x.*y, ...

bb(ir,ic,is), ...

bb(jr,jc,js), ...

'UniformOutput', false);

temp1 = cell2mat(temp);

temp2 = mean(temp1(:));

C1(ir,ic,is,jr,jc,js) = temp2; % 6-D

end

end

end

end

end

end

⇨ Elapsed time is 181.4119 seconds.

% Vectorized method (~3000x faster!)

mm = m/cellsize; % =4

nn = n/cellsize; % =4

b = reshape(cc, [cellsize mm cellsize nn p]);

b = permute(b, [1 3 2 4 5]); % 16 x 16 x 4 x 4 x 100

b = reshape(b, cellsize^2, [])/cellsize; ...