bitcount

版本 1.0.2 (2.0 KB) 作者: Matlab Pro
Count the number of set bits in each element. Time and memory efficient
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更新时间 2025/3/26

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bitcount Counts the number of set bits in each element
Usage:
B = bitcount(A)
Counts the number '1' bits in each element
B = bitcount(A, bitValue)
"bitValue" = 1 = default = counts the occurance of '1'
if bitValue = 0; counts the number '0'
The total bits to verify is [8,16,32,or 64] based on the maximal value of A
B = bitcount(A, bitValue, maxBits)
the total # of bits to examine
Ref: https://www.mathworks.com/matlabcentral/fileexchange/44371-bitcount-bitwise-hamming-distance
The "bitcount" I have implemented here - is much more time/memory efficient vs the Ref above
Efficiency evaluation test: x 10:
maxData = 1e4;
data = uint32(randi([1,intmax('uint32')],1,maxData));
tic;cell2mat(arrayfun(@(x) sum(bitget(x,1:32)),data,'UniformOutput',false)');t_elapsed1 = toc;
tic;bitcount(data);t_elapsed2 = toc;
eff = t_elapsed1 / t_elapsed2;
maxData = 1e4: eff = 10
maxData = 1e5: eff = 20
maxData = 5e5: eff = 40
maxData = 1e6: eff = 56
maxData = 1e7: eff = 128
Examples:
data = 0:15;
out = bitcount(data);
bin_representation = cellfun(@(x) dec2bin(x,4),num2cell(data),'uni',0)';
nBits = num2cell(out)';
disp([num2cell(data(:)), bin_representation, nBits])
% Counts the #'0', default # of bits to examine = 8
data = 0:15;
out = bitcount(data,0); % out = [8 7 7 6 7 6 6 5 7 6 6 5 6 5 5 4]
% Counts the #'0', # of bits to examine = 4
data = 0:15;
out = bitcount(data,0,4); % out = [4 3 3 2 3 2 2 1 3 2 2 1 2 1 1 0]
Created by Noah Safra May 2025

引用格式

Matlab Pro (2025). bitcount (https://www.mathworks.com/matlabcentral/fileexchange/180507-bitcount), MATLAB Central File Exchange. 检索时间: .

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版本 已发布 发行说明
1.0.2

Improved interface
1.0.1

Now enabling also '0' count
1.0.0