I have made a function which calculates the index of a point to which an arbitrary point on a polygon made of XY points belong.This is a visual representation:And this is the function I made:stock GetNodeIndexFromPolygonIndex(polygonid,Polygon_Size){    new polid = (polygonid - (polygonid % 2));    new mid = Polygon_Size/2;    if(polid > mid)    {        polid /= 2;        return (mid - (++polid));    }    else    {        polid /= 2;        if(polid == 0)        {            return 0;          }        return --polid;    }}Is there anything I can optimize here?  This function is going to be called ~2000 times in the worst case in one run on a single threaded application. I would like this to be as optimal as possible.  Is it already?
Optimizing mathematical index calculation function
optimization;computational geometry;pawn
First, I do not know anything about PAWN.Does it have a profiler? Can any profiler be used? If yes, probably use it.If no, write at least some test units to measure execution time.I will assume typical language elements. I will assume polygonid > 0 and Polygon_Size > 0, because I do not know (and did not find in short time) the behavior of / and % for negative numbers.As far as I understood, there is a virtual machine between compiler and execution. This makes things a little bit more complex, but well, we will assume that nothing special happens there.Some of the optimizations could change nothing, because the compiler already does it. I can not predict or test it.That said, I will choose line after line. I do not know if you can change the algorithm, because like Cygal I do not understand the exact purpose.new polid = (polygonid - (polygonid % 2));This makes polid the next smallest even number? % is rather costly, you could either do a polygonid & 1 instead of polygonid % 2 or new polid = polygonid & (max_value - 1) which will set all bits, but the last one to zero. max_value - 1 should be precalculated.new mid = Polygon_Size/2;Change to: new mid = Polygon_Size >> 1 This will be done most probably by the compiler anyway, but we do not know, so lets try it.polid /= 2;This is calculated in both branches. It could help to do it before the branching:new polid_half = polid >> 1;...return (mid - (++polid));This depends on the language details. It could be that ++polid as preincrement operator will load polid, update it by one, and store polid back. We do not plan to use the modified polid, so we could try return (mid - polid + 1) assuming that ++polid is not some magic fast special instruction compared to the normal +.    if(polid == 0)    {        return 0;    }This does only happen if polygonid is 0 or 1. If this happens a lot, you should return immediately at the beginning, saving all the rest:if (polygonid < 2 )  //assuming polygonid > 0    return 0;And remove the check inside the else branch.    return --polid;Same as before, it could be better to return polid - 1Depending on the branch prediction handling, it could be better to have only one return point, not one in every branch. You could introduce a return value and set it according to the current logic.I would try one change after the next and profile every step. All together, it could be:stock GetNodeIndexFromPolygonIndex(polygonid,Polygon_Size){    if (polygonid < 2 )  //assuming polygonid > 0        return 0;    new result = 0;    new polid = polygonid & (max_value - 1); //polid is a bad name    new polid_half = polid >> 1;    new mid = Polygon_Size >> 1;    if(polid > mid)        result = mid - polid_half + 1;    else        result = polid_half - 1;    return result;}