Return a function instead of calling it (in safe_eval)

[vloncar]

If quantizer is a function (like binary_tanh or hard_sigmoid, used as activations), safe_eval would try to make an instance of it and fail. This was due to the change introduced in #12. We should check if quantizer is class to be instantiated before being called or a function ready to be called.

[zhuangh]

Have you tried

x = QConv2D(64, (3, 3), strides=(2,2), kernel_quantizer=binary_tanh, bias_quantizer=quantized_bits(4,0,1), name="conv2d_1_m", activation="hard_sigmoid")(x)
x = QActivation("hard_sigmoid")(x)

Does it work?

[zhuangh]

please add comment here, something like "check the quantizer is a class"

[vloncar]

x = QConv2D(64, (3, 3), strides=(2,2), kernel_quantizer=binary_tanh, bias_quantizer=quantized_bits(4,0,1), name="conv2d_1_m", activation="hard_sigmoid")(x)
x = QActivation("hard_sigmoid")(x)

I tried, but if i understand correctly, this is not how quantizers are intended to be used. The first hard_sigmoid is Keras's one, and the second one is QKeras's one and we never use this combination in our models. It would be useful to be able to use QKeras activations without using QActivation layer, but that is a separate issue (which we can look into).

[zhuangh]

Since the PR is for "If quantizer is a function (like binary_tanh or hard_sigmoid, used as activations), ...", I just want to try whether it can be used in activation inside a qkeras layers and QActivation layer directly.

[vloncar]

Using QConv2d(..., activation='some_qkeras_activation'...) won't work (but we are interested in having that). Using QActivation('some_qkeras_activation'..) works for all quantizers. Combining the two doesn't make sense, i.e., anything before QAactivation should be activation=None or activation='linear'.

[zhuangh]

put this PR into internal system review.

[vloncar]

Is there anything else I should do for this PR?

[zhuangh]

sorry about the late. no for now. I am waiting for feedback from another googler (required by the internal flow).