VERY ODD Function calling time

[Jonathan Rea]

I did the following little test and was surprised by the results, why is the
"Initial : " time so slow ??? surely it should be faster than either of the
other two calls as it lacks a function call. I really dont get this...

i get the following output ....
Initial : 00:00:05.2031250
NonRef : 00:00:03.4062500
Ref : 00:00:04.1562500
Initial : 00:00:05.1406250
NonRef : 00:00:03.1875000
Ref : 00:00:03.9843750

Many thanks
Jon Rea

private void main()
{
int[] bob = new int[100000];
int repCount = 10000;
// initialise the bob array
for( int i = 0; i < length; i++ )
{
bob = 2;
}
DateTime T1;
DateTime T2;
TimeSpan TS1;
// now loop many times trying different calls
while(true)
{

T1 = DateTime.Now; // record the time
for( int j = 0; j < repCount; j++ )
{
for( int i = 0; i < bob.Length; i++ )
{
bob = 2;
}
}
T2 = DateTime.Now;
TS1 = T2 - T1;
Debug.WriteLine( "Initial : " + TS1.ToString() ); // for some reason this is
much slower than the two below ...


T1 = DateTime.Now;
for( int j = 0; j < repCount; j++ )
{
play( bob );
}
T2 = DateTime.Now;
TS1 = T2 - T1;
Debug.WriteLine( "NonRef : " + TS1.ToString() ); // why is this the fastes
method, surely the above is just an inline version of this ???


T1 = DateTime.Now;
for( int j = 0; j < repCount; j++ )
{
play( ref bob );
}
T2 = DateTime.Now;
TS1 = T2 - T1;
Debug.WriteLine( "Ref : " + TS1.ToString() );
}
}

// the following two function calls for interaction with the bob array, bob
is passed in one by ref in one and normally in the other

private void play( int[] b )
{
for( int i = 0; i < b.Length; i++ )
{
b = 2;
}


}
private void play( ref int[] b )
{
for( int i = 0; i < b.Length; i++ )
{
b = 2;
}
}

 

[Niki Estner]

I've disassemled the respective parts, and it seems to me like the non-Ref
version could enregister the counter variable i, while it's on the stack in
the other two versions.

Niki