speed up this function

2015 6 2
2 个回答
更新时间：2021 8 20
4 次查看（30 天）

0 个投票

function [RKey] = Shuffle1R( Key1 )
% Using algorithm to specify the key back for shuffling
stime=tic;
% Key1=[162,28,62,124,78,14,116,133,164,141,109,160,84,16,60,11,32,119,49,150,26,118,77,42,8,115,161,56,123,106,75,98,130,79,155,55,151,167,57,95,45,93,101,46,65,40,64,68,125,52,66,12,3,86,128,135,108,19,145,166,85,156,27,90,17,33,91,157,168,29,34,63,96,18,4,58,67,153,111,104,131,51,94,73,154,83,43,149,54,10,59,39,97,158,140,137,53,38,120,21,92,129,107,47,37,148,82,71,41,36,7,143,61,152,139,165,113,48,9,87,100,74,126,22,69,99,102,20,121,163,169,1,142,81,103,159,112,76,70,72,13,144,25,146,138,24,5,30,6,2,114,23,35,44,122,134,136,80,127,15,88,89,50,132,31,147,110,105,117];
% k=size(Key1,2);
RKey=zeros(1,0)*zeros(0,size(Key1,2));
[~,Ind ]=min(Key1(:));
RKey(:)=Ind;
Key1(Ind)=10000;
toc(stime);
end

1 个评论
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sundus
sundus 2015-6-5
编辑：Walter Roberson 2015-6-5
% function [RKey] = Shuffle1R( Key1 )
% Using algorithm to specify the key back for shuffling
Key1=[162,28,62,124,78,14,116,133,164,141,109,160,84,16,60,11,32,119,49,150,26,118,77,42,8,115,161,56,123,106,75,98,130,79,155,55,151,167,57,95,45,93,101,46,65,40,64,68,125,52,66,12,3,86,128,135,108,19,145,166,85,156,27,90,17,33,91,157,168,29,34,63,96,18,4,58,67,153,111,104,131,51,94,73,154,83,43,149,54,10,59,39,97,158,140,137,53,38,120,21,92,129,107,47,37,148,82,71,41,36,7,143,61,152,139,165,113,48,9,87,100,74,126,22,69,99,102,20,121,163,169,1,142,81,103,159,112,76,70,72,13,144,25,146,138,24,5,30,6,2,114,23,35,44,122,134,136,80,127,15,88,89,50,132,31,147,110,105,117];
stime=tic;
RKey=zeros(1,numel(Key1));
for i=1:numel(Key1),
[j,Ind ]=min(Key1(:));
RKey(i)=Ind;
Key1(Ind)=10000;
end
RKey
toc(stime);
% end

回答（2 个）

Jan
Jan 2015-6-2
编辑：Jan 2015-6-2

0 个投票

function [RKey] = Shuffle1R( Key1 )
[~, Ind] = min(Key1(:));
RKey(1:size(Key1, 2)) = Ind;
end
Notes:
  • zeros(1,0)*zeros(0,size(Key1,2)) is worse than zeros(1, size(Key1, 2))
  • Key1(Ind)=10000 can be omitted

3 个评论
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sundus
sundus 2015-6-5
Hi Jan, with this answer, all the elements of RKey will be the same value: which is 132 that means the position of the smallest element.what I need is the position for all the elements from the smallest to the largest. thank you.
Walter Roberson
Walter Roberson 2015-6-5
Your code to be sped up has no loop to find the ordering of the elements, it only does the min() once. It assigns the result to RKey(:) which means to write to all elements. Jan's answer replicates that behavior. If you want a different behavior to be sped up you will need to supply that code.
sundus
sundus 2015-6-5
编辑：per isakson 2015-6-5
Hi Walter, this is the code with the loop:
% function [RKey] = Shuffle1R( Key1 )
% Using algorithm to specify the key back for shuffling
%
Key1=[162,28,62,124,78,14,116,133,164,141,109,160,84,16,60,11,32,119,49,150,26,118,77,42,8,115,161,56,123,106,75,98,130,79,155,55,151,167,57,95,45,93,101,46,65,40,64,68,125,52,66,12,3,86,128,135,108,19,145,166,85,156,27,90,17,33,91,157,168,29,34,63,96,18,4,58,67,153,111,104,131,51,94,73,154,83,43,149,54,10,59,39,97,158,140,137,53,38,120,21,92,129,107,47,37,148,82,71,41,36,7,143,61,152,139,165,113,48,9,87,100,74,126,22,69,99,102,20,121,163,169,1,142,81,103,159,112,76,70,72,13,144,25,146,138,24,5,30,6,2,114,23,35,44,122,134,136,80,127,15,88,89,50,132,31,147,110,105,117];
%
stime=tic;
RKey=zeros(1,numel(Key1));
for i=1:numel(Key1),
[j,Ind ]=min(Key1(:));
RKey(i)=Ind;
Key1(Ind)=10000;
end
RKey
toc(stime);
% end
Walter Roberson
Walter Roberson 2015-6-5

0 个投票

function [RKey] = Shuffle1R( Key1 )
[~, ~, RKey] = unique(Key1);
end

1 个评论
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sundus
sundus 2015-6-5
Thank you Walter, you are right, so I send the code with the loop.

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sundus
sundus
2015-6-2

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