If you want to generate cascade with OpenCV training tools, you should be ready for waiting plenty of time. For example, on training set: 3000 positive / 5000 negative, it takes about 6 days! to get cascade for face detection. I wanted to generate many cascades with different training sets, also I added my own features to standart OpenCV’s ones and refactor algorithms a little bit. So waiting for 6 days to understand, that your cascade does nothing good =) was really anoying. To reduce time, I chose paralleling methods.