enforce fail at CPUAllocator.cpp:56 about tch-rs

[LaurentMazare]

I think this just means that you ran out of memory. Below is your stack-trace with more formatting.
Looking at the man page of posix_memalign, it can return the error code ENOMEM which value is 12 and corresponds to your error.
As of why you ran out of memory, it's hard to tell without more context. The only thing that the stack-trace tells us is that it happens on the backward pass of some matrix multiplication.

thread 'main' panicked at 'called `Result::unwrap()` on an `Err`
 value: TorchError { c_error: "[enforce fail at CPUAllocator.cpp:56] posix_memalign(&data, gAlignment,
nbytes) == 0. 12 vs 0
frame #0: std::function<std::string ()>::operator()() const + 0x11 (0x7ffbfd74c441
inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libc10.so)
frame #1:
c10::ThrowEnforceNotMet(char const*, int, char const*, std::string const&, void const*) + 0x49
(0x7ffbfd74c259 inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libc10.so)
frame #2: c10::alloc_cpu(unsigned long) + 0x65e (0x7ffbfd73546e inn/target/debug
/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libc10.so)
frame #3: <unknown function> +
0x13dca (0x7ffbfd736dca inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libc10.so)
frame #4: THStorage_resize + 0x76 (0x7ffbf40aa8b6 inn/target/debug/build/torch-
sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libcaffe2.so)
frame #5:
at::native::resize_cpu_(at::Tensor&, c10::ArrayRef<long>) + 0x38f (0x7ffbf3d014df inn/target/debug
/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libcaffe2.so)
frame #6: <unknown function>
+ 0xb2cb6e (0x7ffbf3e5ab6e inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libcaffe2.so)
frame #7: at::Tensor::resize_(c10::ArrayRef<long>) + 0x4d (0x55777ea3df2b in
target/debug/pytorch-image-classification)
frame #8: <unknown function> + 0xb3d18c
(0x7ffbf3e6b18c inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libcaffe2.so)
frame #9: at::native::mm(at::Tensor const&, at::Tensor const&) + 0x65
(0x7ffbf3c7a485 inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libcaffe2.so)
frame #10: at::TypeDefault::mm(at::Tensor const&, at::Tensor const&) const + 0x5d
(0x7ffbf4013a8d inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libcaffe2.so)
frame #11: torch::autograd::VariableType::mm(at::Tensor const&, at::Tensor const&)
const + 0x6ea (0x7ffbf27059fa inn/target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libtorch.so.1)
frame #12: <unknown function> + 0x3238ea (0x7ffbf22488ea in target/debug/build
/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libtorch.so.1)
frame #13:
torch::autograd::generated::MmBackward::apply(std::vector<torch::autograd::Variable,
std::allocator<torch::autograd::Variable> >&&) + 0x170 (0x7ffbf227b750 in target/debug/build/torch-
sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libtorch.so.1)
frame #14: <unknown function> +
0x30cd5a (0x7ffbf2231d5a in target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch
/lib/libtorch.so.1)
frame #15:
torch::autograd::Engine::evaluate_function(torch::autograd::FunctionTask&) + 0x385 (0x7ffbf222ae25
in /target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libtorch.so.1)
frame #16:
torch::autograd::Engine::thread_main(torch::autograd::GraphTask*) + 0xc0 (0x7ffbf222ce20 in
target/debug/build/torch-sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libtorch.so.1)
frame #17:
torch::autograd::Engine::thread_init(int) + 0x136 (0x7ffbf222a1f6 inn/target/debug/build/torch-
sys-8ab344225acfe8de/out/libtorch/libtorch/lib/libtorch.so.1)
frame #18: <unknown function> +
0xbd9e0 (0x7ffbfda229e0 in /usr/lib/x86_64-linux-gnu/libstdc++.so.6)
frame #19: <unknown function>
+ 0x76db (0x7ffbf19016db in /lib/x86_64-linux-gnu/libpthread.so.0)
frame #20: clone + 0x3f
(0x7ffbf141288f in /lib/x86_64-linux-gnu/libc.so.6)
" }', src/libcore/result.rs:997:5

[infinite-Joy]

So this error means that the process ran out of memory. Thanks for the clarification.