% vectorize_contrast.m
% 程序向量化和循環(huán)結(jié)構(gòu)的比較
% 1.不預(yù)設(shè)數(shù)組比較程序的執(zhí)行時(shí)間
max=10000;
disp('方法一：不預(yù)設(shè)數(shù)組比較執(zhí)行時(shí)間')
tic;
for i=1:max
    clear sqr;
    for j=1:max
        sqr=sqrt(i);
    end
end
toc;
disp(['\t所用時(shí)間為' toc]);
disp('方法二：預(yù)設(shè)數(shù)組比較執(zhí)行時(shí)間')
tic;
for i=1:max
    clear sqr;
    sqr=zeros(1,max);
    for j=1:max
        sqr=sqrt(i);
    end
end
toc;
disp(['\t所用時(shí)間為' toc]);
disp('方法：預(yù)設(shè)數(shù)組比較執(zhí)行時(shí)間')
tic;
for i=1:max
    clear sqr;
    sqr=zeros(1,max);
    for j=1:max
        sqr=sqrt(i);
    end
end
toc;
disp(['\t所用時(shí)間為' toc]);