I am new to Caffe2, and I want to compose an operation like this:
My question is, how to compose Caffe2 operators to make the same operators like above? I have tried some compositions but still I couldn't find the right one. If anyone knows the composition, please help, I will be really appreciate for it.
There is a Gather operator in Caffe2. The main problem with this operator is that you can't set the axis (it's always 0). So, if we run this code:
model = ModelHelper(name="test")
s = np.arange(20).reshape(4, 5)
y = np.asarray([0, 1, 2])
workspace.FeedBlob('s', s.astype(np.float32))
workspace.FeedBlob('y', y.astype(np.int32))
model.net.Gather(['s', 'y'], ['out'])
workspace.RunNetOnce(model.net)
out = workspace.FetchBlob('out')
print(out)
We will get:
[[ 0. 1. 2. 3. 4.]
[ 5. 6. 7. 8. 9.]
[ 10. 11. 12. 13. 14.]]
One solution could be to reshape s to a 1D array and transform y in the same way. First of all, we have to implement an operator to transform y. In this case, we will use a numpy function called ravel_multi_index:
class RavelMultiIndexOp(object):
def forward(self, inputs, outputs):
blob_out = outputs[0]
index = np.ravel_multi_index(inputs[0].data, inputs[1].shape)
blob_out.reshape(index.shape)
blob_out.data[...] = index
Now, we can reimplement our original code:
model = ModelHelper(name="test")
s = np.arange(20).reshape(4, 5)
y = np.asarray([[0, 1, 2],[0, 1, 2]])
workspace.FeedBlob('s', s.astype(np.float32))
workspace.FeedBlob('y', y.astype(np.int32))
model.net.Python(RavelMultiIndexOp().forward)(
['y', 's'], ['y'], name='RavelMultiIndex'
)
model.net.Reshape('s', ['s_reshaped', 's_old'], shape=(-1, 1))
model.net.Gather(['s_reshaped', 'y'], ['out'])
workspace.RunNetOnce(model.net)
out = workspace.FetchBlob('out')
print(out)
Output:
[[ 0.]
[ 6.]
[ 12.]]
You may want to reshape it to (1, -1).