Parfor loop problem with SVM classification

Question

Eghbal 2013-11-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106057-parfor-loop-problem-with-svm-classification

评论： Edric Ellis 2013-11-25

Hi. I have a problem for paralleling a SVM Classification. In my code I repeat 3 times a 5-fold cross validation of SVM and average the accuracy of it. I want to paralell the main loop of 3 times repeat of cross validation but when I use parfor in this loop the program doesn't use all performance of 2 Cores of my CPU and only use 60% of the performance!.

Thank you so much

Code :

    parfor L=1:NumOFLoops;
    indices = crossvalind('Kfold',QQ,NumOfKfold);
    cp = classperf(QQ);
    for m=1:NumOfKfold;
    test = (indices == m); Train = ~test;
    testI=zeros(numel(test>0),1);
    TrainInputs=INPUT(Train,:);
    TrainTargets=QQ(Train,:);
    TestInputs=INPUT(test,:);
    %%SVM Structure
      svmstruct=svmtrain(TrainInputs,TrainTargets,...
     'boxconstraint',Penalty,...
     'kernel_function','rbf','method','QP',...
     'rbf_sigma',Sigma)
      TestOutputs=svmclassify(svmstruct,TestInputs,'showplot',false);
      classperf(cp,TestOutputs,test);
    end
    Error(:,L)=cp.ErrorRate;         
    end
    Results.ErrorRate=(sum(Error))/NumOFLoops;

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Edric Ellis 2013-11-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106057-parfor-loop-problem-with-svm-classification#answer_115175

If you're using R2013a or earlier, you need to explicitly open a matlabpool before running the PARFOR loop using "matlabpool('local', 2)". R2013b does this for you automatically.

Also, if you only have 3 iterations that can run in parallel, the best speedup you can hope for is 1.5 since one worker will have to perform two of the iterations.

2 个评论
显示无隐藏无

Eghbal 2013-11-14

编辑：Eghbal 2013-11-14

Thank you so much for your reply. Yes. I'm suing R2013b. I increase numbers of parfor loop to 8 but the max performance in two cores in Task Manager is 73-75!. Two matlab in task manager are running.Two 32-35% processing. When I compared it with normal processing(1 core), the total performance is similar in two cases. for and parfor.

Thanks,