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Subject: [boost] [Heaps] benchmarks
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2011-06-07 17:32:20

Dear All,

I have done some quick benchmarks; the code can be found here:

This is a "work queue", i.e. it's a queue of
boost::function<void(void)> "work items" with float priorities. It's
similar to a real application with fast (burst) fill and gradual drain;
the pattern here is 10 pushes and 1 pop, repeated until all the work
has been added, and then all of the work is popped in sequence. The
priorities are essentially random, and there are 100 000 items in total.

Currently my real application uses a std::multimap. I've compared that
with a std::vector using std::push|pop_heap, std::priority_queue using
std::vector and std::deque, and the proposed heap::priority_queue and heap::b_heap.

The columns below are median-of-3 runtimes in seconds for:

1. 50 runs on a 32-bit 3 GHz AMD Athlon II Linux system, using g++
4.4.4 -O4.
2. 10 runs on a 32-bit 1.2 GHz VIA C7-M Linux syste, using g++4.4.2 -O4.
3. 5 runs on a 1.2 GHz ARMv5 Linux system, using g++ 4.4.2 -O4.

std::multimap 3.20 3.69 3.37
std::vector + std::push|pop_heap 2.35 3.36 2.71
std::priority_queue<vector> 2.58 3.48 2.84
std::priority_queue<deque> 4.27 5.77 3.72
heap::priority_queue 2.49 3.37 2.74
heap::b_heap 5.14 7.62 5.82

I was unable to try the proposed d_ary_heap because I couldn't find a
working syntax for the arity template parameter - any ideas anyone?

The 3 implementations based on std::vector perform similarly, as
expected. I'm a bit surprised that my one is fastest, but the
difference is small. Also as expected the version using multimap is
slower, though maybe not by as much as I had expected.

I was expecting the b_heap to be faster, but it is not; it is
substantially slower. What is going on there? Does it all come down
to size of data, cache size, etc? Ideally, an "improved"
implementation like this would be able to fall back to the naive
implementation in cases where it does not function any better. Or
maybe I'm using it wrongly.

My understanding is that the fibonacci, binomial and other heaps only
improve things when other operations e.g. merging are needed - is that correct?

Regards, Phil.

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