Accelerating MATLAB Performance

69Standard Performance-Tuning Techniques

elseif round(rand)

vec = [0,0,0];

else

vec = [1,1,1];

end

value(idx) = sum(vec);

end

⇨ Elapsed time is 2.459548 seconds.

% Simplified branch code - 1.9x faster

value = zeros(1,1e6);

for idx = 1 : 1e6

if rand >= 0.5

value(idx) = sum(rand([1,3]));

elseif rand < 0.5 % else value=0: unchanged from initialization

value(idx) = 3;

end

end

⇨ Elapsed time is 1.307274 seconds.

3.1.5 Unroll Simple Loops

A technique that is often mentioned in performance-tuning literature is loop unrolling (also

called loop unwinding).

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The idea is to replace a loop with repeated sets of the loop con