Created
August 3, 2018 19:32
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define backward pass
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def backward_grads(self, y, dy, training=True): | |
dy1, dy2 = dy | |
y1, y2 = y | |
with tf.GradientTape() as gtape: | |
gtape.watch(y1) | |
gy1 = self.g(y1, training=training) | |
grads_combined = gtape.gradient( | |
gy1, [y1] + self.g.trainable_variables, output_gradients=dy2) | |
dg = grads_combined[1:] | |
dx1 = dy1 + grads_combined[0] | |
x2 = y2 - gy1 | |
with tf.GradientTape() as ftape: | |
ftape.watch(x2) | |
fx2 = self.f(x2, training=training) | |
grads_combined = ftape.gradient( | |
fx2, [x2] + self.f.trainable_variables, output_gradients=dx1) | |
df = grads_combined[1:] | |
dx2 = dy2 + grads_combined[0] | |
x1 = y1 - fx2 | |
x = x1, x2 | |
dx = dx1, dx2 | |
grads = df + dg | |
return x, dx, grads |
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