Optimizer Questions

[Knobi der Rechnerschrat]

Hallo,

  I've got some questions about the optimizer levels for the C (and F77)
compiler on a 70GT.

  - compared to the -g flag that we use for pgm developement, using -O2
    results in a much greater speed increase than the step from -O2 to -O3.
    Taking the much greater compile/link times for -O3 into account, the
    question arises whether it is worth using -O3 or not. Especially, are
    there cases where -O3 is REALLY advantegous over -O2?

  - what is the difference between -O3 and -O4? -O4 seems not to be documented
    and it results in the same speedups than -O3.

Regards
Martin Knoblauch

TH-Darmstadt
Physical Chemistry 1 (soon: Center for Molecular Modelling)
Petersenstrasse 20
D-6100 Darmstadt, FRG

BITNET: <XBR2D96D at DDATHD21>