COPTFLAGS is meant for optimization flags but CFLAGS should also work. However since each of them have their own defaults - you would use the correct one to override the defaults.
If the option you specify is not picked up - mostlikely petsc configure attempted to use it - and configure rejected it. You'll have to send us configure.log to figureout why they were rejected. Satish On Wed, 7 Mar 2018, Lucas Clemente Vella wrote: > Despite documentation and output from "./configure --help", PETSC > disregards completely all of the below: > > --CFLAGS=<string> > --CXXFLAGS=<string> > --FFLAGS=<string> > --COPTFLAGS=<string> > --FOPTFLAGS=<string> > --CXXOPTFLAGS=<string> > > And also the customary environment variables CFLAGS and CXXFLAGS. > > How can I set special optimization flags, like enabling of SIMD > instructions? > >