Modifying large arrays slower than modifying structure arrays?
11 次查看(过去 30 天)
显示 更早的评论
I'm having issues with my code where I noticed manipulating large matrix arrays is extremely slow.
In my original implementation, I have to read in some data from a binary file using a for loop. I noticed that if I inserted the data into an array of structures instead of putting the data directly into an initialized matrix array, my performance was much better. I'm not sure why this is happening? Could someone provide me with some insight?
Below is a representative example of the performance issues I'm seeing.
% set up raw data
n = 10000;
rawNum = (1:n);
rawData = magic(n); % if n==10000, data is about 0.75 GB
% struct example
simpleStruct.num = [];
simpleStruct.data = [];
S(n,1) = simpleStruct;
tic
for i=1:n
S(i).num = rawNum(i);
S(i).data = rawData(i,:);
end
fprintf("Time took to populate struct array: %1.3f seconds.\n",toc);
% array example
arrayNum = zeros(n,1);
arrayData = zeros(n,n);
tic
for i=1:n
arrayNum(i) = rawNum(i);
arrayData(i,:) = rawData(i,:);
end
fprintf("Time took to populate plain ole array: %1.3f seconds.\n",toc);
0 个评论
采纳的回答
Walter Roberson
2019-9-11
Row versus column ordering effects.
>> tic;for i = 1:n; arrayNum(i) = rawNum(i); arrayData(i,:) = rawData(i,:); end;toc
Elapsed time is 2.254735 seconds.
>> tic;for i = 1:n; arrayNum(i) = rawNum(i); arrayData(:,i) = rawData(:,i); end;toc
Elapsed time is 0.196039 seconds.
2 个评论
更多回答(0 个)
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!