Unlike the other GPU linear algebra kernels that I've ported so far, this one isn't straightforward to implement as a single kernel, and while it does support lowering without access to a GPU (no more descriptor!), it only supports dynamics shapes in the batch dimensions. There are two main technical challenges:
1. The main `gesvd` kernels in cuSolver/hipSolver only support matrices with shape `(m, n)` with `m >= n`. This means that we need to transpose the inputs and outputs as part of the lowering rule when `m < n`. (Note: we actually just use C layouts instead of Fortran layouts to implement this case.) While this could be handled in the kernel, this seemed like a lot of work for somewhat limited benefit, and it would probably have performance implications.
2. The `gesvd` and `gesvdj` kernels return `V^H` and `V` respectively, and the batched version of `gesvdj` doesn't support `full_matrices=False`. This means that we need logic in the lowering rule to handle transposition and slicing. This makes it hard to have the algorithm selection be a parameter to the kernel.
Another note: cuSolver has a 64-bit implementation of the SVD, and we always use that implementation on the CUDA backend. The 32-bit interface is included for ROCM support, and I have tested it manually. This was a feature request from https://github.com/jax-ml/jax/issues/23413.
PiperOrigin-RevId: 676839182
There is a lot of boilerplate required for each new custom call to cuSolver / cuBLAS, and having both the FFI logic and the framework wrappers in the same library was getting unwieldy. This change adds a new "interface" target which just includes the shims to wrap cuSolver/BLAS functions, and then these are used from `solver_kernels_ffi` where the FFI logic lives.
PiperOrigin-RevId: 673832309
