MATLAB POLYSPACE RELEASE NOTES Manuale Utente Scaricare il pdf (Pagina 170)

100

101

4 Programming

Preallocation

If you cannot vec

torize a piece of code, you can make your

for loops g o faster

by preallocatin

g any vectors or arrays in which output results are stored. For

example, this co

de uses the function

zeros to preallocate the vector created in

the

for loop. Th

is makes the

for loop execute significantly faster:

r = zeros(32,1);

for n = 1:32

r(n) = rank(magic(n));

end

Without the prea

llocation in the previous example, the M ATLAB interpreter

enlarges the

r v

ector by one elem ent each time through the loop. Vector

preallocation

eliminates this step and res ults in faster execution.

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