I am trying to figure out why "Choice A" performs better that "Choice B". My test shows something like 228 vs 830 or there about, it's like a 4 x difference. Looking at the IL, the untrained eye doesn't pick-out the subtly between the 2 calls.
Thank you, Stephen
const int SIZE = 10000;
void Main()
{
var sw = Stopwatch.StartNew();
int[,]A = new int[SIZE, SIZE];
int total, x, y;
// Choice A
total = 0;
for (x = 0; x < SIZE; x++)
{
for (y = 0; y < SIZE; y++)
{
total += A[x, y];
}
}
Console.WriteLine(sw.ElapsedMilliseconds);
sw.Reset();
sw.Start();
// Choice B
total = 0;
for (y = 0; y < SIZE; y++)
{
for (x = 0; x < SIZE; x++)
{
total += A[x, y];
}
}
Console.WriteLine(sw.ElapsedMilliseconds);
}
// Define other methods and classes here
Ok, I broke this out so that they would run independently of each other and mitigate any caching and or diagnostics... and B is ALWAYS coming in behind A
namespace ConsoleApplication1
{
class ProgramA
{
const int SIZE = 10000;
static void Main(string[] args)
{
var sw = Stopwatch.StartNew();
int[,] A = new int[SIZE, SIZE];
int total, x, y;
// Choice A
total = 0;
for (x = 0; x < SIZE; x++)
{
for (y = 0; y < SIZE; y++)
{
total += A[x, y];
}
}
Console.WriteLine(sw.ElapsedMilliseconds);
Console.ReadLine();
}
}
class ProgramB
{
const int SIZE = 10000;
static void Main(string[] args)
{
var sw = Stopwatch.StartNew();
int[,] A = new int[SIZE, SIZE];
int total, x, y;
// Choice B
total = 0;
for (y = 0; y < SIZE; y++)
{
for (x = 0; x < SIZE; x++)
{
total += A[x, y];
}
}
Console.WriteLine(sw.ElapsedMilliseconds);
Console.ReadLine();
}
}
}
