Re: gcj Linpack performance

["Tim Prince" <tprince at computer dot org>]

Did you investigate which compiler flags for gcj gave the best
performance?  I would have
thought -Os -march=pentiumpro -ffast-math -funroll-loops a likely first
guess.
----- Original Message -----
From: "Florian Schintke" <schintke@zib.de>
To: <gcc@gcc.gnu.org>
Sent: Tuesday, July 10, 2001 3:35 AM
Subject: gcj Linpack performance


> Hi all,
>
> I just tested the performace of gcj 3.0 with the Linpack
> benchmark
> http://www.netlib.org/benchmark/linpackjava/Linpack.java
> and got the following results:
>
> The used system
> > uname -a
> Linux host 2.2.18 #1 Fri Jan 19 22:10:35 GMT 2001 i686 unknown
> > cat /proc/cpuinfo
> processor       : 0
> vendor_id       : GenuineIntel
> cpu family      : 6
> model           : 8
> model name      : Pentium III (Coppermine)
> stepping        : 3
> cpu MHz         : 797.559
> cache size      : 256 KB
> fdiv_bug        : no
> hlt_bug         : no
> sep_bug         : no
> f00f_bug        : no
> coma_bug        : no
> fpu             : yes
> fpu_exception   : yes
> cpuid level     : 2
> wp              : yes
> flags           : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca
> cmov pat pse36 mmx fxsr xmm
> bogomips        : 1592.52
>
>
> 256MB main memory
>
> ###### gcj
> > gcc -v
> Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0/specs
> Configured with: ./configure
> Thread model: single
> gcc version 3.0
> > gcj --version
> 3.0
> > gcj -O3 --main=Linpack -funroll-all-loops Linpack.java
> > ./a.out
>
> Mflops/s: 24.833  Time: 1.73 secs  Norm Res: 4.7
> Precision: 2.220446049250313E-16
>
> ###### java 1.1.8
> > /usr/lib/java/bin/java -version
> java version "1.1.8"
> > /usr/lib/java/bin/javac Linpack.java
> > /usr/lib/java/bin/java Linpack
>
> Mflops/s: 4.812  Time: 8.93 secs  Norm Res: 6.34
> Precision: 2.220446049250313E-16
>
> ###### IBM java JDK 1.3.0
> > /usr/lib/jdk1.3/bin/java -version
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
> Classic VM (build 1.3.0, J2RE 1.3.0 IBM build cx130-20001025 (JIT
> enabled: jitc))
> > /usr/lib/jdk1.3/bin/javac Linpack.java
> > /usr/lib/jdk1.3/bin/java Linpack
> Mflops/s: 46.877  Time: 0.92 secs  Norm Res: 6.54
> Precision: 2.220446049250313E-16
>
> ###### Compiled with java 1.1.8, executed with IBM JIT
> > /usr/lib/java/bin/java -version
> java version "1.1.8"
> > /usr/lib/java/bin/javac Linpack.java
> > /usr/lib/jdk1.3/bin/java -version
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
> Classic VM (build 1.3.0, J2RE 1.3.0 IBM build cx130-20001025 (JIT
> enabled: jitc))
> > /usr/lib/jdk1.3/bin/java Linpack
> Mflops/s: 44.778  Time: 0.96 secs  Norm Res: 6.54
> Precision: 2.220446049250313E-16
>
>
> Why is gcj not as fast as IBMs JIT compiler?
> Maybe this info helps you to look how to improve the performance.
>
>
> Florian Schintke
> --
> Florian Schintke <schintke@zib.de>, http://www.zib.de/schintke/
>