DTree classifier crashes without error message (Bug #4480)

Added by Tom Krause over 9 years ago. Updated over 9 years ago.

Status:New Start date:2015-07-10
Priority:Normal Due date:
Assignee:- % Done:

0%
Category:ml
Target version:-
Affected version:branch 'master' (3.0-dev) Operating System:Linux
Difficulty:Medium HW Platform:x64
Pull request:

Description

When try to use the DTrees in OpenCV 3.0 the "train" method crashes without give an error message.

I tried many configurations, but here is a very simple example.

cv::Mat sampleMat = cv::Mat(10,2, CV_32FC1);
cv::Mat labelMat = cv::Mat(10,1, CV_32SC1);

float* sampleData = (float*)sampleMat.data;
        int* labelData = (int*)labelMat.data;
(*sampleData++) = 1.f; (*sampleData++) = 1.f; (*labelData++) = 1;
        (*sampleData++) = 1.f; (*sampleData++) = 3.f; (*labelData++) = 1;
        (*sampleData++) = 2.f; (*sampleData++) = 8.f; (*labelData++) = 1;
        (*sampleData++) = 1.f; (*sampleData++) = 23.f; (*labelData++) = 1;
        (*sampleData++) = 2.f; (*sampleData++) = 546.f; (*labelData++) = 1;
(*sampleData++) = 4.f; (*sampleData++) = 1.f; (*labelData++) = 2;
        (*sampleData++) = 3.f; (*sampleData++) = 3.f; (*labelData++) = 2;
        (*sampleData++) = 4.f; (*sampleData++) = 8.f; (*labelData++) = 2;
        (*sampleData++) = 4.f; (*sampleData++) = 23.f; (*labelData++) = 2;
        (*sampleData++) = 5.f; (*sampleData++) = 546.f; (*labelData++) = 2;
cv::Ptr<cv::ml::TrainData> trainData = cv::ml::TrainData::create(sampleMat, cv::ml::ROW_SAMPLE, labelMat);
cv::Ptr<cv::ml::DTrees> dtree = cv::ml::DTrees::create();
        dtree->train(trainData);

History

#1
Updated by Tom Krause over 9 years ago

i found a message in the terminal, maybe this helps a little bit:

"terminate called after throwing an instance of 'std::length_error'
what(): vector::reserve"

#2
Updated by be rak over 9 years ago

i can reproduce it, if we don't set maxdepth, the default value of MAX_INT is used, and it tries to allocate absurd sizes here:


int DTreesImpl::addTree(const vector<int>& sidx )
{
    size_t n = (params.getMaxDepth() > 0 ? (1 << params.getMaxDepth()) : 1024) + w->wnodes.size();

    w->wnodes.reserve(n);
    w->wsplits.reserve(n);
    w->wsubsets.reserve(n*w->maxSubsetSize);
    ...

#3
Updated by Tom Krause over 9 years ago

When setting the maxDepth. Then the program crashes without an error message.

So it seems there is another bug.

#4
Updated by be rak over 9 years ago

yes, true. if CVFolds is left at the default value 10 (or !=0 in general), it crashes in DTreesImpl::calcValue, line 517:

            for( i = 0; i < n; i++ )
            {
                int si = _sidx[i];
                j = w->cv_labels[si]; k = w->cat_responses[si];
                cv_cls_count[j*m + k] += w->sample_weights[si];
            }

w->cv_labels is not initialized / empty.

the 2.4 branch assigned the cv_labels: https://github.com/Itseez/opencv/blob/2.4/modules/ml/src/tree.cpp#L2749 , this part seems missing.

#5
Updated by Maksim Shabunin over 9 years ago

Issue has been transferred to GitHub: https://github.com/Itseez/opencv/issues/5070

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