Re: Timing of functions in C#
- From: "Floyd Burger" <floyd@xxxxxxxxxxxx>
- Date: Sat, 2 Apr 2005 08:55:35 -0700
The first time a method is called it is JIT'd. The Just In Time compiler
will compile the IDL, then will use the compiled version for subsequent
calls.
--
Floyd
"DrOrbit" <nlsa@xxxxxxxx> wrote in message
news:1112456865.214794.71490@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>I am working on a rather large program that hits several methods
> multiple times. In looking for ways to speed it up, I have discovered
> something odd. The first time I call a method, it's about 30 times
> slower than any subsequent call. This is true for all the methods that
> I have tested. For example, the first call might take 30 milliseconds
> whereas all subsequent calls take less than 1 ms. I would like to
> understand why this is happening.
>
> An example method looks like this:
>
> public void computeVecP () // Escobal 5.3
> {
> VecP.X = (SatObs.Sat.KepElements.CosArgPerigee *
> SatObs.Sat.KepElements.CosLongAsc) -
> (SatObs.Sat.KepElements.SinArgPerigee *
> SatObs.Sat.KepElements.SinLongAsc * SatObs.Sat.KepElements.CosInc);
>
> VecP.Y = (SatObs.Sat.KepElements.CosArgPerigee *
> SatObs.Sat.KepElements.SinLongAsc) +
> (SatObs.Sat.KepElements.SinArgPerigee *
> SatObs.Sat.KepElements.CosLongAsc * SatObs.Sat.KepElements.CosInc);
>
> VecP.Z = SatObs.Sat.KepElements.SinArgPerigee *
> SatObs.Sat.KepElements.SinInc;
> }
>
> Each term is "a property of a property of a property" and all values
> have been pre-computed. In other words,
> "SatObs.Sat.KepElements.CosArgPerigee" is declared as
> public double CosArgPerigee{get{return cosArgPerigee;}
> set{cosArgPerigee=value;}}
>
> If I substitute simple variables (i.e. "X" for
> "SatObs.Sat.KepElements.CosArgPerigee") then the time difference
> disappears. Therefore I conclude that C# is spending a long time
> locating the first property look-up but somehow doesn't need to do it
> again for subsequent calls. I hope that I'm making sense here. Is
> there a better or more complete explanation?
>
.
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