Goal

Make a common GPU ndarray(n dimensions array) that can be reused by all projects that is as future proof as possible, while keeping it easy to use for simple need/quick test.

Motivation

  • Currently there are at least 6 different GPU arrays in python
    • CudaNdarray(Theano), GPUArray(pycuda), CUDAMatrix(cudamat), GPUArray(pyopencl), Clyther, Copperhead, ...
    • There are even more if we include other languages.
  • They are incompatible
    • None have the same properties and interface
  • All of them are a subset of NumPy.ndarray on the GPU!

Design Goals

  • Have a n dimensional array.
    • Otherwise, not all project can reuse it. And you never know when you will need more dimensions.
  • Support many data types (int, float, double).
    • Otherwise, we are limited in what we can do with it.
  • Support strided view, c and f memory layout
    • This lowers memory usage and memory copies. A scarce resource on GPU.
    • You never know which memory layout is the best for your future need.
  • Be compatible with CUDA and OpenCL
    • You never know the future. Also, this make it possible to support other future language.
  • Make it easy to support just a subset of the feature.
    • If you just want to test something that support only CUDA and c contiguous matrices, it will stay easy as without libgpuarray.
    • There is functionality to make the same code work and compile with both CUDA and OpenCL. You don’t need to use them.
  • Have the base object in C to allow collaboration with more projects.
    • We want people from C, C++, ruby, R, ... all use the same base GPU ndarray.
  • Have a python binding separate from the c code.

  • Support mixed back-end OpenCL/CUDA in the same binary.
    • But still keep it easy to use only one.
    • This would allow an easier transition to a new platform if the need come.
  • Support dynamic compilation
    • This allow optimization at run time based on the shapes for example.
    • You don’t need to use this.

In the end, we need a NumPy ndarray on the GPU! There is a restriction that does not allow us to reuse that object directly, but you will find it very similar.