JornAggror Blog

I have another little optimization for you.

Always use pre incrementing values where possible, like ++i instead of i++.

So simple, yet, I have never come accross it before.

 

If you think about its very logical. You called each for iteration a function compared to call it once and save the result temporarly.

 

Another good optimization is for two dimensional array, take care of your traversing order e,g.

// creation
unsigned char** myarray = new unsigned char*[1024];
for (int i = 0; i < 1024; ++i)
{
   myarray[i] = new unsigned char;
}

// update
for(int y = 0; y < 1024; ++y)
{
for(int x = 0; x < 1024; ++x)
{
 myarray[y][x] = 0;  // swapping x and y results in decrease/increase of nearly 50% on my system .... its because cache misses and miss prediction of cpu.
}
}

Neat. Didn't know you could do that.

@Dadonik: What is the gain when using a pre-incremented value?

@Furbolg: Thanks for sharing

i have a hard enough time keeping track of a single iterator...

 

 

--Mike

The i++ version creates a temporary copy of i, increases i by one and returns the copy.

The ++i version just increases the value of i by one and returns it.

for( int i=veryLongArray.length(); i>0;)
{
       DoSomething(--i);
}