automatic-differentiation

Why don’t C++ compilers do better constant folding?

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This is because Eigen explicitly vectorize your code as 3 vmulpd, 2 vaddpd and 1 horizontal reduction within the remaining 4 component registers (this assumes AVX, with SSE only you’ll get 6 mulpd and 5 addpd). With -ffast-math GCC and clang are allowed to remove the last 2 vmulpd and vaddpd (and this is what … Read more

What does the parameter retain_graph mean in the Variable’s backward() method?

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@cleros is pretty on the point about the use of retain_graph=True. In essence, it will retain any necessary information to calculate a certain variable, so that we can do backward pass on it. An illustrative example Suppose that we have a computation graph shown above. The variable d and e is the output, and a … Read more