Re: JAVA LINPAC

[johnhazel@xxxxxxxxxxxxx]

On Sun, 10 June 2001, bob@acm.org wrote:

> 
> 
> >...the test results were 27MFLOPS on Windows ME and onlt 2.7MFLOPS on LINUX
> >Mandrake 7.2 (installed using defaults).......... 
> Such a large difference ought to be clearly visible as a response time issue;

It certianly was. Half a minut execution vs <4 seconds. All the Linux flavors I have experimented with were noticably slower than an equivalent task run on Windows. This is particularily true of screen/window redraws. Could the problem be there in the screen redraw? This can be a big killer for Excel worksheets if you don't disable screen refreshes during calculations. There are no redraws needed in running this JAVA LINPAC but that doesn't mean the machine isn't doing them anyway.


http://www.netlib.org/benchmark/linpackjava/Linpack.java

(BTW I'm looking for a reasonable Excel substitution, all candidates so far have been terribly slow and lacking features.StarOffice, Gnumeric etc. That led me to look at JAVA)


> I wonder about the timing tools in use here,

This is the timing methodl I found in the source: http://www.netlib.org/benchmark/linpackjava/Linpack.java

 time = second();
    /* Factor a.  */
    info = dgefa(a,lda,n,ipvt);
    /* Solve ax=b. */
    dgesl(a,lda,n,ipvt,b,0);
 total = second() - time;

> and I'd cross check it (sometimes
> tough results can be crosschecked by simple means) using a stop watch in both
> cases. You're not looking for perfect accuracy here, but broad verification
> that things are as bad as is claimed.

As I mentioned above, the time is <4 sec for Windows and >30sec for Linux.

> 
> >Why the pathetic Linux JAVA performance? There must be some key OS issue.
> Could be... could also be a process-accounting issue, and perhaps a JVM or 
> application coding issue.

The same code is used for either Win or Lin. However the suggestion of the problem being in the JVM sure sounds reasonable. How could I check this? I don't feel qualified to dig it out of the JVM source myself.

John Hazel

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