How to optimize complex if statement

Programming Questions

paul.stro..

How to optimize complex if statement

in Programming Questions • 2 years ago

I have this beast in my code:

if(pixel[0][5] < 800 || pixel[0][6] < 800 || pixel[0][4] < 800 ||
pixel[1][4] < 800 || pixel[1][5] < 800 || pixel[1][6] < 800 || pixel[1][7] < 800 || pixel[1][3] < 800 ||
pixel[2][4] < 800 || pixel[2][5] < 800 || pixel[2][6] < 800 || pixel[2][7] < 800 || pixel[2][3] < 900||
pixel[3][4] < 800 || pixel[3][5] < 800 || pixel[3][6] < 800 || pixel[3][7] < 800 || pixel[3][3] < 800 ||
pixel[4][5] < 800 || pixel[4][6] < 800 || pixel[4][7] < 800)
{ do something }

any suggestions on how to simplify this?

context: I have a large array of data, and need to trigger certain actions when one value of a specific group reaches a certain number.

If someone could suggest a better way of 'asking' this, that would be amazing. (or point me to a tutorial)

Thanks

p.

Replies(2)

allonestr..

Re: How to optimize complex if statement

2 years ago

Two methods come to mind, assuming that this dataset is representative.

//middle rows
for(int i = 0; i < 5; i++)
{
for(int j = 3; j < 8; j++)
{
    if(pixel[i][j] < 800)
    {
      doSomething;
    }
}
}
//top and bottom rows
for(int i = 0; i < 5; i++)
{
for(int j = 4; j < 7; j+=3)
{
    if(pixel[i][j] < 800)
    {
      doSomething;
    }
}
}

If this set is representative, then I'd stick this into a function, passing it the centre pixel, say. And then looking at this centre pixel, you could derive the set by testing for distance from this centre pixel.

//centre of circle pixel[ci][cjy];
for(int i = 0; i < boundx; i++)
{
for(int j = 0; j < boundy; j++)
{
    dx = pixel[ci][cj].x - pixel[i][j].x;
    dy = pixel[ci][cj].y - pixel[i][j].y;
    distance = sqrt(dx*dx + dy*dy);
    if(distance < 3)
    {
      doSomething;
    }
}
}

add to this some test for the centre pixel < 800. Again, stick this into a function.

If the 900 is intentional rather than a typo, then you need just add a single test for that.

PhiLho

Re: How to optimize complex if statement

2 years ago

One way to do this:

int[][] coords =
{
{ 4, 5, 6 },
{ 3, 4, 5, 6, 7 },
{ 3, 4, 5, 6, 7 },
{ 3, 4, 5, 6, 7 },
{ 5, 6, 7 },
};
// Test
int[][] pixel =
{
{ 100, 200, 300, 100, 200, 300, 100, 200 },
{ 100, 200, 300, 100, 200, 300, 100, 200 },
{ 100, 200, 300, 100, 200, 300, 100, 200 },
{ 100, 200, 300, 900, 200, 300, 100, 200 },
{ 100, 200, 300, 100, 200, 300, 100, 200 },
{ 100, 200, 300, 100, 200, 300, 100, 200 },
};
boolean bOK = true;
fails:
for (int x = 0; x < 5; x++)
{
int[] ys = coords[x];
for (int y : ys)
{
if (pixel[x][y] >= 800)
{
bOK = false;
break fails; // No need for further tests
}
}
}
if (bOK)
{
// Do something
println("All indicators are green!");
}