FreeBSD 5.2 v/s FreeBSD 4.9 MFLOPS performance (gcc3.3.3 v/s gcc2.9.5)

[Juan Tumani]

Hi,

I have an Intel D845GE m/b w/ a P4 1.7 CPU and I have the box setup to dual 
boot
to either 4.9 or 5.2.  Both OS are right off the latest posted iso CD image, 
i.e., no updates,
no kernel tweaks, everything vanilla right out of the box.  I compiled 
flops.c on both 4.9
and 5.2 and the 5.2 performance is less than half that of 4.9: 760 MFLOPS on 
4.9 v/s
340 MFLOPS on 5.2.

I tried turning off the SMP and other kernel tweaks and no improvement in 
5.2.  I then
downloaded and installed gcc295 on the 5.2 machine and that fixed the 
problem.  So
now all I have to do is figure out the gcc 3.3.3 switches to make it run 
like gcc 2.9.5 or
figure out how to rebuild 5.2 w/ gcc 2.9.5 :-).

Anyone know what's going on w/ gcc 3.3.3 ?

%gcc295 flops.c -o flops
%./flops

   FLOPS C Program (Double Precision)
       Version 1.2, 29 Feb 1992

   PI: Program     =  3.14159265358999429
   PI: Reference   =  3.14159265358979312
   PI: Error       =   2.0117e-13

   Area: Program   =  0.50000000000008060
   Area: Reference =  0.50000000000000000
   Area: Error     =   8.0602e-14

   Iterations      =  20000000
   BenchTime(usec) =    0.0013
   Scalar MFLOPS   =  760.2353

%gcc flops.c -o flops
%./flops

   FLOPS C Program (Double Precision)
       Version 1.2, 29 Feb 1992

   PI: Program     =  3.14159265358999429
   PI: Reference   =  3.14159265358979312
   PI: Error       =   2.0117e-13

   Area: Program   =  0.50000000000008060
   Area: Reference =  0.50000000000000000
   Area: Error     =   8.0602e-14

   Iterations      =  20000000
   BenchTime(usec) =    0.0029
   Scalar MFLOPS   =  339.4571

%

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