[Haskell-cafe] Data.Array.Accelerate initialization timings

[Manuel M T Chakravarty]

Martin Dybdal:
> On 20 February 2012 16:39, Paul Sujkov <psujkov at gmail.com> wrote:
>> Ah, it seems that I see now what's going wrong way. I'm not using the 'run'
>> function from the CUDA backend, and so by default I guess the code is
>> interpreted (the test backend used for semantics check). However, it's not
>> perfectly clear how to use CUDA backend explicitly.
> 
> Neither the interpreter or the CUDA code are used in your example.
> Everything in Data.Array.Accelerate are front-end stuff, your arrays
> are allocated on the host, so it is here there is an inefficiency.
> 
> The "use" method inserts a statement in the syntax tree generated by
> the front-end, which the back-end can use as a hint to transfer that
> array to the GPU, while compiling the rest of the program into CUDA
> code. The Data.Array.Accelerate.CUDA.run function is the one that
> actually moves the arrays to the GPU.
> 
> I haven't tried executing your code and I'm not sure why the front-end
> is that slow.

The 'fromList' function is mostly meant for testing or to initialise small arrays.  It is not particularly optimised.  (Going via a vanilla list is just a bad idea if you want performance.)

For efficient data marshalling have a look at the modules under Data.Array.Accelerate.IO.

Manuel