Contains and contains_subrange parallel algorithm implementation GSOC 2024

[Zak-K-Abdi]

Implementing parallel algorithms for contains and contains_subrange. GSOC 2024 proposal.
Will attempt to fix hpx::search so hpx::contains_subrange can make a call to hpx::search.

[jenkins-cscs]

Can one of the admins verify this patch?

[Pansysk75]

This is probably work-in-progress, but I just want to mention that util::loop_pred doesn't actually use the execution policy to run in parallel, so this will not run in multiple threads. You'll have to use a partitioner, which splits the work and launches it on multiple (the equal algorithm is a a nice example).

[Zak-K-Abdi]

Ah I was unaware at the time I wrote that, I should have been more mindful of what I was using. I checked out equal algorithm and I made some changes that now use the partitioner in the parallel overload. Also, I was hesitant to do this but I created a file in the parallel/algorithms/detail called contains.hpp, holding the implementation details for the algorithm.

[codacy-production]

Coverage summary from Codacy

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Coverage variation	Diff coverage
✅ -0.10%	✅ 90.96%

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	Coverable lines	Covered lines	Coverage
Common ancestor commit (f4ff6e8)	232431	198777	85.52%
Head commit (1b22fae)	205360 (-27071)	175429 (-23348)	85.43% (-0.10%)

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	Coverable lines	Covered lines	Diff coverage
Pull request (#6497)	509	463	90.96%

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[hkaiser]

@Zak-K-Abdi: Please take a look at the clang-format problems (https://gist.github.com/hkaiser/26bced03497017f481dbb9ee7d0df67c) and the cmake issues:

Missing hpx/parallel/algorithms/detail/contains.hpp in libs/core/algorithms/CMakeLists.txt

Also here is the list of inspect issues reported:

/libs/core/algorithms/include/hpx/parallel/algorithms/contains.hpp: END file doesn't end with a newline, Endline Whitespace: 74, C, Lic, SPDX-Lic
/libs/core/algorithms/include/hpx/parallel/algorithms/detail/contains.hpp: END file doesn't end with a newline, C, Lic, SPDX-Lic

[Zak-K-Abdi]

@Pansysk75 Hi Panos, I'm not sure if this is correct, could you check this line of code I changed? I changed the helper function to return hpx::future, a continuation to the previous future, by using .then().

[Pansysk75]

That looks right, i think you might want to capture last by value and not by reference, as it is a local variable of the parallel function. Otherwise looks good!

[Pansysk75]

I think returning contains_subrange_helper<ExPolicy, FwdIter1>().get(itr, last1) would suffice here.
The return types of your helper function already match with algorithm_result_t. Calling that additional ::get will call .get() on your future before returning it, which undermines your latest change on your helper.