Hi This could be useful for optimising sorting and search, since GAP is very slow.
Can it deal with lists of GAP objects, like groups and tuples? Sandeep Murthy s.mur...@mykolab.com > On 1 Apr 2015, at 12:20, Christopher Jefferson <ca...@st-andrews.ac.uk> wrote: > > Ever wish you could just write C and C++ code in GAP? Well now you can, > with the gapcpp package from: https://github.com/ChrisJefferson/gapcpp > > After running './configure' in the packages directory and loading it, you > will find one method, 'CompileMethod', which accepts C++ (or C) code, the > name of your function and it's number of arguments. The function is then > automatically linked into GAP, and GAP types turned into C++ types (and > vice versa). > > Here's an easy example: > > gap> fun := CompileMethod("int f(int X) { return X; }", "f", 1);; > gap> fun(3); > 3 > > That's fairly boring however. Let's consider something more interesting! > > Perhaps we want to sort a list of integers by their last digit: > > gap> SortBy([1..1000000], x -> x mod 10);; > gap> time; > 548 > > Hmm.. Lets give that 'mod' function some C++ power! > > gap> m := CompileMethod("int f(int X) { return X % 10; }", "f", 1);; > gap> SortBy([1..1000000], m);; > gap> time > 487 > > Hmm, a little speedup, but not as much as we would like. Let's push the > whole thing into C++, using new 'triple quotes' to make the code easier > to write (in the master branch of GAP, not package specific!) > > gap> x := CompileMethod(""" > bool comp(int i, int j) > { return i%10 < j%10; } > std::vector<int> sb(std::vector<int> i) > { std::sort(i.begin(), i.end(),comp); return i; }""", "sb", 1); > gap> x([1..1000000]);; > gap> time; > 48 > > Wow, 10x speedup! > > Of course, C++ lets us do new things. Perhaps we really wish we had a > stable sort? No problem! > > gap> x := CompileMethod(""" > bool comp(int i, int j) > { return i%10 < j%10; } > std::vector<int> sb(std::vector<int> i) > { std::stable_sort(i.begin(), i.end(),comp); return i; }""", "sb", 1); > gap> x([1..1000000]);; > gap> time; > 124 > > A little slower, but with the bonus of being stable! > > Let's try some more things: > > gap> PartialSums([1..50000]);; > gap> time; > 26021 > > gap> x := CompileMethod(""" > #include <numeric> > std::vector<int> sums(std::vector<int> v) > { > std::vector<int> out(v.size()); > // r means 'reverse', we do this to agree with GAP's order > std::partial_sum(v.rbegin(), v.rend(), out.rbegin()); > return out; > }""", "sums", 1);; > gap> PartialSums([1..50000]);; > gap> time; > 1 > > The following C++ types are currently supported (recursively). More types > can be added on request! > > std::vector > std::list > std::deque > std::pair > std::string > int > Bool > vec1 (a custom vector type which is 1-indexed, for each GAP<->C++ > integration) > > optional (a way of marking missing values, so std::vector<optional<int> > > supports lists with missing values, unlike std::vector<int>) > > If you understand GAP, You can also use Obj and all the normal GAP method > to access objects. There is also initial support for gap records (see the > tests for examples). > > > I am interested in any requests for improvements, or usage of this package > (or wished usages of this package). > > > Chris > > > _______________________________________________ > Forum mailing list > Forum@mail.gap-system.org > http://mail.gap-system.org/mailman/listinfo/forum
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