Use maskedCopy to select elements in a tensor

maskedCopy.txt

th> mask=torch.ByteTensor(10, 3):random(2):add(-1)
                                                                      [0.0001s]
th> mask
 1  0  1
 0  1  1
 1  1  1
 1  1  0
 0  1  1
 1  1  0
 1  0  1
 0  0  0
 0  1  1
 1  0  1
[torch.ByteTensor of size 10x3]

                                                                      [0.0002s]
th> x = torch.Tensor(10,3):uniform()
                                                                      [0.0001s]
th> x
 0.2936  0.3001  0.7200
 0.8701  0.9548  0.1079
 0.4744  0.9558  0.2796
 0.2058  0.2744  0.5256
 0.1091  0.9623  0.6479
 0.0420  0.7619  0.7688
 0.4613  0.8468  0.9257
 0.1426  0.7731  0.9501
 0.8959  0.2475  0.7301
 0.6407  0.2878  0.7172
[torch.DoubleTensor of size 10x3]

                                                                      [0.0002s]
th> y=torch.Tensor(x:size()):maskedCopy(mask, x[mask])
                                                                      [0.0001s]
th> y
 0.2936  0.0000  0.7200
 0.0000  0.9548  0.1079
 0.4744  0.9558  0.2796
 0.2058  0.2744  0.0000
 0.0000  0.9623  0.6479
 0.0420  0.7619  0.0000
 0.4613  0.0000  0.9257
 0.0000  0.0000  0.0000
 0.0000  0.2475  0.7301
 0.6407  0.0000  0.7172
[torch.DoubleTensor of size 10x3]

                                                                      [0.0003s]