nouiz/Theano — comment on commit 6174405c6b1ed988e66ea07c788f12d9e0432a4c
File:  line 0
By jaberg:

Interesting - did this actually come up in usage? How are negative strides handled on CPU?

Anyway, this brings to mind a special case that if *both* x.stride < 0 and A.stride[0] < 0 then no copy is needed because you can do the whole dot-product backward. Same thing for y.stride and A.stride[1]. This same thinking goes for the CPU implementation as well. But it's a tricky thing to write and test (would take an hour or two at least) so how about adding this text as a comment, or making a ticket for it. Someone trying to optimize his backward GER / GEMM may some day implement it.