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2014-05-28 12:08:48 -0600 | commented question | Adaboost Influence Trimming Takes Longer to Train I apologize as the data may be confusing. The base case here is when influence trimming is disabled. That gives an accuracy of 95.03 and a train time of 10.607. When influence trimming is turned on (with the default of 0.95), the accuracy drops to 94.94 as expected, but the training time takes 5x as long. |
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2014-05-28 11:12:37 -0600 | asked a question | Adaboost Influence Trimming Takes Longer to Train The documentation states that influence trimming can be used "to reduce the computation time for boosted models with substantially losing accuracy". By default, the weight_trim_rate parameter is 0.95. After disabling influence training by changing that parameter to 0, I actually achieve a large speed-up. When using a dataset with 262144 samples, I achieve a 5x speed-up. When using a dataset ten times larger, I achieve a 3x speed-up. This seems to be the opposite of the expected behavior. Can anyone explain why this might be happening? Thanks! |
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2012-10-18 12:43:26 -0600 | asked a question | Problem Reading PNG with Transparency layer I'm using 2.3.1 and am having problems loading a PNG file. An example picture is given below. Apparently the background of this image is transparent. You can see this because I can grab the alpha layer using imagemagick. The output from imagemagick is shown below. The problem is that when I load the image using imread, the matrix becomes the output shown below. I have tried loading the image with -1, 0, and 1 as flags and nothing has helped. When I load it with -1, it has 4 channels, but the 4th channel just contains all zeros. Has anyone seen something similar to this before? |