Re: [boost] Synchronization (RE: [compute] review)

Subject: Re: [boost] Synchronization (RE: [compute] review)
From: Kyle Lutz (kyle.r.lutz_at_[hidden])
Date: 2014-12-29 11:56:14

On Mon, Dec 29, 2014 at 1:21 AM, Thomas M <firespot71_at_[hidden]> wrote:
> On 29/12/2014 03:23, Kyle Lutz wrote:
>>
>> On Sun, Dec 28, 2014 at 6:16 PM, Gruenke,Matt <mgruenke_at_[hidden]>
>> wrote:
>>>
>>> -----Original Message-----
>>> From: Boost [mailto:boost-bounces_at_[hidden]] On Behalf Of Kyle Lutz
>>> Sent: Sunday, December 28, 2014 20:36
>>> To: boost_at_[hidden] List
>>> Subject: Re: [boost] Synchronization (RE: [compute] review)
>>>
>>>> On Sun, Dec 28, 2014 at 4:46 PM, Gruenke,Matt wrote:
>>>
>>>
>>>>> My understanding, based on comments you've made to other reviewers, is
>>>>> that functions like boost::compute::transform() are asynchronous when
>>>>> the result is on the device, but block when the result is on the host.
>>>>> This is what I'm concerned about.  Is it true?
>>>
>>>
>>>> Yes this is correct. In general, algorithms like transform() are
>>>> asynchronous
>>>> when the input/output ranges are both on the device and synchronous when
>>>> one
>>>> of the ranges is on the host. I'll work on better ways to allow
>>>> asynchrony in
>>>> the latter case. One of my current ideas is add asynchronous
>>>> memory-mapping
>>>> support to the mapped_view class [1] which can then be used with any of
>>>> the
>>>> algorithms in an asynchronous fashion.
>
>
> When you speak of input/output ranges on the host, to what kinds of
> iterators do you refer to? Any input/output iterator kind (e.g. iterators
> from a std:: container -> just tried a std::vector on
> boost::compute::transform, didn't compile if provided as input range), or
> iterators that are part of your library?

In general, all of the algorithms operate on Boost.Compute iterators
rather than STL iterators. The main exception to this rule is the
boost::compute::copy() algorithm which copies between ranges of STL
iterators on the host and Boost.Compute iterators on the device.
Anther exception is the boost::compute::sort() algorithm which can
directly sort ranges of random-access iterators on the host (as long
as the data is contiguous, e.g. std::vector<T>). I am working to add
more direct support for host ranges to the other algorithms. Currently
the best way to use the Boost.Compute algorithms together with host
memory is with the mapped_view [1] class.

-kyle

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