CODEWITHSUNDEEP
c#.netperformancemultidimensional-array
Don
Don

Reputation: 11

C# computationally expensive , how to make it faster

I know its a dumb question to ask about , why this code minX is computationally expensive, but i thought, someone might inform me of my mistake. Thanks

// getMap is a 2 dimentional array of type short I need to find maxX,minX,maxY,minY 
//Can't use Math.Min , as it will get the lower bound i.e 0, i want values after filtering
for (int X = 0; X < getMap.GetLength(0); X++)
{       
    for (int Y = 0; Y < getMap.GetLength(1); Y++)
    {           
        if((short)getMap.GetValue(X,Y) !=  0)
        {
           //if i take it out, it works fine ,I need to 
            if (minX > X )
                minX = X;
            else
                X = minX;
        // Prints some stuff and does other computation 
        }
    }
}
// Draws image

Upvotes: 0

Views: 246

Answers (2)

Henk Holterman
Henk Holterman

Reputation: 273244

I don't know how (short)getMap.GetValue(X,Y) compares to just getmap[X,Y] but is seems over-complicated.

What you can do is to replace short[,] getMap with short[][] getMap.

Array-of-array (jagged arrays) are ususally faster in these nested loop scenarios because the Jitter can optimize range checking better.

Upvotes: 1

CodesInChaos
CodesInChaos

Reputation: 108790

the else X = minX; part doesn't make much sense. It can cause an endless loop because you're setting back the loop variable X to a lower value.

Your code will only terminate if at most 1 column contains a non zero value(assuming you initialized minX to a large value).

For example assume that both the X=0 and the X=1 column contain a non zero value somewhere. Then when it hits the non zero value in the 0 column minX is set to 0. Then later it hits the non zero value with X=1 notices that minX>X is false and sets X back to 0. And repeat forever.

Upvotes: 4

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