Re: Profiling puzzle

"mcek" <>
2 May 2006 09:35:00 -0700
Oliver Wong wrote:

"mcek" <> wrote in message

Hi All!

I was profiling my app using TPTP in Eclipse and I found one thing I
don't understand. The following method takes almost the whole time of
the execution and what concerns me is that the Base Time is 96% of the
Cumulative Time.

from help:
Base Time:
For any invocation, the base time is the time taken to execute the
invocation, excluding the time spent in other methods that were called
during the invocation.

Cumulative Time:
For any invocation, the cumulative time is the time taken to execute
all methods called from an invocation. If an invocation has no
additional method calls, then the cumulative time will be equal to the
base time.

But when I look at the method:

       public evacuationSimulator2005.Point3D getPoint3D( String name
               String strX = getProperty( name + "X" );
               String strY = getProperty( name + "Y" );
               String strZ = getProperty( name + "Z" );

               return( new evacuationSimulator2005.Point3D(
                       Double.parseDouble( strX ),
                       Double.parseDouble( strY ),
                       Double.parseDouble( strZ ) ) );

I cannot see what is it doing apart from calling other methods, so what
is happening all this time?

    String concatenation. (e.g. name + "X").

    An old profiling story I like to tell is my buddy wrote some math
processing program which took less than 1 second to run, but my buddy wanted
to optimize it anyway. So he took out his book on numerical processing and
thought up ways to improve the speed of the arithmetic expression he was
working with. I told him to profile, and when he did, he found out that
string concatenation was taking up almost all of the time within the method.
That is to say, the slowest part of his code was this:

System.out.println("The answer is " + answer);

    Java is really fast a math, not so fast at String manipulation.

The '+' operator is converted to the append() method, so it doesn't
count to the Base Time either.

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