BufferedArrays

Arrays written completely with native Julia code.

This package is an attempt to demonstrate how an array backed by a native Julia memory buffer can be implemented in a performant manner. Attempts have been made to follow similar cache-coherent storage of the array dimensions as Base.Array.

Quick start

BArray is a subtype of DenseArray and therefore much of the functionality of Base is inherited (including access to BLAS and LAPACK). Currently only very simple constructors are implemented.

v = BVector{Int}(10)
m = BMatrix{Float64}(4,4)
a = BArray{Complex{Float64}}((2,2,2,2))

Like Base.Array, these constructors return arrays with unintialized storage. However, the BArray cannot be resized after construction.

Future work may add support for Generators in constructors and convenience function similar to zeros, ones and fill.

Discussion

The main caveats seem to be:

• Only works for isbits element types. I have no idea how to register that a region of memory contains pointers that the GC should care about, or how to unregister that upon finalization.

• Double inderiction resulting from the fact that the Buffer is a type containing a pointer. Future work on the Julia compiler which would inline the pointer in the Buffer to the stack would remove the double indirection. (note: due the the fact that Base.Array is resizeable, it is the author's understanding that a similar double-indirection problem exists there too).

• I should remove run-time overhead of 1-based indexing (similarly possible for any indexing offset).

• The garbage collector will believe the size of BArray is that of a pointer, and may not prioritize deallocation of large arrays. A method to guide the GC on the "real" number of bytes deallocated would be useful both here and for interoperability outside of Julia.

• Performance needs to be measured carefully. At least for a subset of functions, performance is similar to Base.Array.

• Aliasing issues have not been addressed to the extent of Base.Array.

• It is assumed that the pointer in the buffer will never change - it would be nice if that field could be set constant.