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

To Vinnie, The Visual Studio have a problem with and or , xor, and need to include the file ciso646. In others compilers, this file exist but is empty, because the compiler accept them. The code is correct, because I compiled and run benchmarks in Windows and Linux, without problem. The only problem are in the test files. They need to include ciso646. I included in all the programs, and run with b2, and in my machine, they run correctly without errors. I compiled again with GCC 5.2 , and as expected, compile and run. The files corrected are uploaded to the repository. To Marc, about pthread, it’s only a library. If you do a static compilation , don’t need pthread for run the programs. In all the parallel algorithms, you have a parameter with the number of threads to use, by default is std::thread::hardware_concurrency ( ), and depend of the HW where execute the program. If the value passed is 0, the algorithm uses 1 thread. This parameter is not fixed in the compilation time, it’s a variable. The algorithm check when begin the execution, and configure and adapt the algorithm to the number of threads. If you want to check easily in Windows and Linux, in a separate repository (because it uses license-restricted software like TBB and Microsoft parallel sort, and can’t be included in the Boost library), you can find all the code needed to run the benchmarks, the library code, the benchmark programs, and shell scripts to compile and run For the Linux benchmarks you will need to have installed TBB. (https://github.com/fjtapia/ https://github.com/fjtapia/sort_parallel_benchmark) (https://github.com/fjtapia/sort_parallel_benchmark) https://github.com/fjtapia/sort_parallel_benchmark Thanks by your interest Francisco 2016-11-11 16:13 GMT+01:00 Marc Glisse :

On Fri, 11 Nov 2016, Steven Ross wrote:

Dear Boost community,

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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

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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:

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

GCC parallel_sort

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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:

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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

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