Re: [boost] [sort] Parallel sorting sub-library mini-review starts tomorrow, 11 November

On Fri, 11 Nov 2016, Steven Ross wrote:

Dear Boost community,

The mini-review of Francisco Tapia's Parallel sorting library begins tomorrow November 11, and ends November 20th. The purpose of this review is to assess whether the sub-library is useful and up to Boost software standards. If the Boost community agrees on both, Francisco and I will integrate it into the existing Boost.sort library as a separate sub-library from Spreadsort. In doing so we'll integrate the documentation with the existing documentation for Boost.Sort, making it more consistent.

If you review Francisco's library, please make sure you're using a compiler that supports C++11, and answer each of these questions:

1. Were you able to run it and see accurate and fast results? Please specify your compiler, OS, and processor type, and any problems (or slowdowns) encountered. 2. Would you use this library if accepted? Why or why not? 3. What is your evaluation of the design? 4. What is your evaluation of the implementation? 5. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study?

Sorry, I won't have time to do a full review. I only quickly tested it in my application with g++-6 on x86_64-linux and it just worked :-) I believe I would use it, as an alternative to TBB (I would keep both code paths). Both because of the performance, and because of the lack of dependency: we already depend on C++11 and boost (I don't remember if adding -pthread is still necessary to use std::thread, that might complicate things a bit).

*This library is *include only, only requiring* the files in the boost/sort/parallel folder, with no external dependencies.*

This is an advantage for simplicity, but also a disadvantage in that you cannot easily benefit from sharing a thread pool with other parallel constructs, from a supervisor that adapts the number of threads to whatever else is going on, from any other convenient tool from a framework (omp would let you limit the number of threads with an environment variable, etc).

Results from running on an I7 5820 with 12 threads:

I did a quick test on a dual-core laptop, and this was noticably faster than TBB :-)

GCC parallel_sort

Note that gcc's parallel sort has an extra parameter to chose between several algorithms, it would be nice to mention that you tested the non-default ones as well. On Fri, 11 Nov 2016, Vinnie Falco wrote:

On Thu, Nov 10, 2016 at 8:25 PM, Steven Ross wrote:

...

The library is here: https://github.com/fjtapia/sort_parallel

I was unable to build using Visual Studio 2015 with Update 3. First I cloned the repository into the root of my boost 1.62.0 directory. Then from a mSysGit bash prompt I `cd` to "test/" and invoke `b2`. Here is some of the output:

test_insertion_sort.cpp(97): error C2146: syntax error: missing ')' before identifier 'and' test_insertion_sort.cpp(114): error C2146: syntax error: missing ')' before identifier 'and'

Is "and" standard C++? Most of the errors revolve around that keyword.

Yes, 'and' is standard in C++, but MS only has it in some compilation modes or if you include <ciso646> first. I think boost should not use those alternative tokens. -- Marc Glisse