Re: [boost] [compute] Review comments

Subject: Re: [boost] [compute] Review comments
From: Asbjørn (lordcrc_at_[hidden])
Date: 2014-12-30 07:12:57

On 29.12.2014 01:42, Kyle Lutz wrote:
> On Sun, Dec 28, 2014 at 1:40 PM, Asbjørn <lordcrc_at_[hidden]> wrote:
>> 2) I did miss async versions of the algorithms, so it's possible to chain
>> together multiple calls. Even though all the data sits on the compute
>> device, the overhead of waiting for each operation to finish before queuing
>> the next can make the compute gains completely irrelevant.
>
> Can you let me know what chain of functions you're calling? Many
> algorithms should already execute asynchronously and provide the
> behavior you expect.

Seems I had missed this crucial part. Given that copy() is sync and there's a 
special async version of it, if you forget the details it's easy to forget that 
other operations are enqueued non-blocking. For example, on the reference page 
of transform()[1] there's no mention of it being asynchronous. It makes sense 
assuming the default in-order command queue execution, but I think it should be 
more explicit to make it harder to forget late at night :)

>> 3) I think relevant calls should have a non-throwing form returning an error
>> code, ala Boost.ASIO.
>
> This could be implemented, but would be a large amount of work
> (essentially doubling the size of the public API). Can you let me know
> more about your use-case and why the current exception-based API is
> not suitable?

Fair enough. From experience, the main errors which one can handle sensibly 
would be insufficient memory for a buffer (one can try using smaller 
buffers/reduce dataset/alternate algorithm) and kernels failing to compile/run 
due to lack of registers or similar resources (one can try an alternate 
algorithm/kernel).

For example, using a single large buffer may be significantly faster, but if the 
max buffer size is small, one can switch to a ping-pong algorithm.

[1]: http://kylelutz.github.io/compute/boost/compute/transform.html

Cheers
- Asbjørn