Re: [Starpu-devel] Data interfaces in StarPU

[Cyril Roelandt <cyril.roelandt@inria.fr>]

Hello !

On 08/28/2012 06:48 AM, Albert Sidelnik wrote:
> I was hoping that somebody could explain how/where the routines that are
> part of the data interface system work. I am implementing my own interface
> that is based on the "variable interface" but instead of allocating new
> data or copying data, I only pass pointers around (somewhat similar to the
> cl_arg argument). Maybe I am missing something, but the allocate and copy
> routines never seem to be invoked. If what I am  trying to do is impossible
> or makes no sense, are there any better alternative options of using the
> data management system but without having to allocate data internally?

I am not sure that diving into the internals of StarPU will really help 
you figure out what's going on in your interface.

In order to trigger a a call to your copy function, you could do 
something like this:

1) Register a piece of data on a CPU using your interface
2) Submit a task that must be executed on an OpenCL device (or a CUDA 
device, but not a CPU)
3) StarPU will then try to copy the piece of data you registered to the 
OpenCL device, and will do this by calling the 
"copy_ram_to_opencl_async" function of your interface.

What do you mean by "pass pointers around" ? If you modify the piece of 
data you registered on the CPU, the OpenCL/CUDA pointer is no longer 
pointing to a valid piece of data, so you probably have to make a copy.

Maybe showing us some code could help :)


WBR,
Cyril Roelandt.