How can i do it fast way ?

Question

mankang 2021-2-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/748682-how-can-i-do-it-fast-way

编辑： mankang 2021-2-19

example = mat2cell(rand(100000,4),ones(1,100)*1000,4);
result = cell( size(example, 1), 1);
var1_list = [0.5, 0.7];
var2_list = [0.3, 0.5, 0.7];
final = cell( length(var1_list)*length(var2_list), 1);
cnt = 1;
for var1 = var1_list
    for var2 = var2_list
        for i = 1 : size(example, 1)
            index1 = find( (example{i, 1}(:, 2) >= var1 )==1);
            index2 = find( (example{i, 1}(:, 3) >= var2 )==1);
            index  = intersect(index1, index2);
            if ~isempty(index)
                result{i, 1} = index;
            end
        end
        final{cnt, 1} = result;
        cnt = cnt + 1;
    end
end

How can i do it fast way ? or How can i convert to gpuarray?

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jan 2021-2-18

Ary you really sure, that you do not want to update result{i,1}, if no intersection was found?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2021-2-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/748682-how-can-i-do-it-fast-way#answer_626707

编辑：Jan 2021-2-18

在 MATLAB Online 中打开

3 times faster: Replace

            index1 = find( (example{i, 1}(:, 2) >= var1 )==1);
            index2 = find( (example{i, 1}(:, 3) >= var2 )==1);
            index  = intersect(index1, index2);
            if ~isempty(index)
                result{i, 1} = index;
            end
            

by:

            index1 = find(all(example{i, 1}(:, 2:3) >= [var1, var2], 2));
            if ~isempty(index1)
                result{i, 1} = index1;
            end            

And a further duplication of the speed:

            index1 = (example{i, 1}(:, 2) >= var1 & ...
                      example{i, 1}(:, 3) >= var2);
            if any(index1)
                result{i, 1} = find(index1);
            end            

I'd expect something like

            if any(index)
                result{i, 1} = find(index1);
            else  % Reset value from former iteration?!
                result{i, 1} = [];
            end            

but maybe this behavior is wanted. In the random tests data, this situation never happens. But if you want to set reslut{i} to [], this is faster than the IF-method above:

         index1 = (example{i, 1}(:, 2) >= var1 & ...
                   example{i, 1}(:, 3) >= var2);
         result{i} = find(index1);  % Note: {i} is the same as {i, 1}