Hello Eugene, I have attached a minimum example using the exact typedefs I use in my project.
I am compiling on MacOS with an up-to-date system clang, if that makes any difference. Best wishes, Toby From: Eugene Zhulenev <[email protected]> Reply to: "[email protected]" <[email protected]> Date: Tuesday, 17 December 2019 at 19:31 To: "[email protected]" <[email protected]> Subject: Re: [eigen] Returning Tensor Expressions On Tue, Dec 17, 2019 at 4:15 AM Wood, Tobias <[email protected]<mailto:[email protected]>> wrote: Hello, I am trying to write a finite difference function for Eigen::Tensors. Currently I am using a lambda: auto diff = [](Eigen::Tensor<std::complex<float>, 3> const &a, Eigen::Index const d) { Dims3 const sz{a.dimension(0) - 2, a.dimension(1) - 2, a.dimension(2) - 2}; Dims3 const st1{1, 1, 1}; Dims3 fwd{1, 1, 1}; Dims3 bck{1, 1, 1}; fwd[d] = 2; bck[d] = 0; return (a.slice(fwd, sz) - a.slice(bck, sz)) / a.slice(st1, sz).constant(2.f); }; This works okay. However, I would like to do two things: 1 – Change this from a lambda into a free function. What should the return type of the function be, so that it returns the expression/operation and does not evaluate the tensor into a temporary? 2 – I would prefer to pass in a TensorRef, so I can pass in a .chip() from a 4D tensor without a temporary. When I try to do this with the current lambda, and I am assigning to a slice, e.g. b.chip<3>(0).slice(st1, sz) = diff(a, 0); I get the following error: TensorRef.h:413:51: error: cannot initialize return object of type 'Eigen::TensorEvaluator<const Eigen::TensorRef<Eigen::Tensor<std::__1::complex<float>, 3, 0, long> >, Eigen::ThreadPoolDevice>::Scalar *' (aka 'std::__1::complex<float> *') with an rvalue of type 'const Eigen::TensorRef<Eigen::Tensor<std::__1::complex<float>, 3, 0, long> >::Scalar *' (aka 'const std::__1::complex<float> *') This appears to be complaining that I can’t assign a `const std::complex<float> *` to a `std::complex<float> *`? Can you create a minimal repro for this, can't quite figure out how you try to use TensorRef, and what is the source of `const` in the expression. Looks like a bug somewhere in typedefs. Thanks in advance, Toby
testing.cpp
Description: testing.cpp
