Matlab的：快速的方式来总结在二进制数那些稀疏结构？ [英] Matlab: fast way to sum ones in binary numbers with Sparse structure?

问题描述

的大多数的答案只能解决关于<一个本已回答的问题href=\"http://stackoverflow.com/questions/1024904/calculating-hamming-weight-efficiently-in-matlab\">Hamming 中的权重，但忽略有关点找到和处理稀疏。显然，答案由这里晒 解决有关找到一点 - 但我还不能验证。我的回答这里不利用其他的答案，如bitshifting，但不够好例子回答的聪明才智。的

Most answers only address the already-answered question about Hamming weights but ignore the point about find and dealing with the sparsity. Apparently the answer by Shai here addresses the point about find -- but I am not yet able to verify it. My answer here does not utilise the ingenuity of other answers such as the bitshifting but good enough example answer.

输入

>> mlf=sparse([],[],[],2^31+1,1);mlf(1)=10;mlf(10)=111;mlf(77)=1010;  
>> transpose(dec2bin(find(mlf)))

ans =

001
000
000
011
001
010
101

目标

1
0
0
2
1
1
2    

快速计算那些在二进制数与稀疏结构的金额？

推荐答案

您可以用吨的方式做到这一点。我认为，最简单的是

You can do this in tons of ways. The simplest I think would be

% Example data
F = [268469248 285213696 536904704 553649152];

% Solution 1
sum(dec2bin(F)-'0',2)

和最快的（如发现<一个href=\"http://stackoverflow.com/questions/1024904/calculating-hamming-weight-efficiently-in-matlab\">here):

% Solution 2
w = uint32(F');

p1 = uint32(1431655765);
p2 = uint32(858993459);
p3 = uint32(252645135);
p4 = uint32(16711935);
p5 = uint32(65535);

w = bitand(bitshift(w, -1), p1) + bitand(w, p1);
w = bitand(bitshift(w, -2), p2) + bitand(w, p2);
w = bitand(bitshift(w, -4), p3) + bitand(w, p3);
w = bitand(bitshift(w, -8), p4) + bitand(w, p4);
w = bitand(bitshift(w,-16), p5) + bitand(w, p5);

这篇关于Matlab的：快速的方式来总结在二进制数那些稀疏结构？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！