Re: quation about automake with additional optimization

From: Christian Holm Christensen (cholm@hehi03.nbi.dk)
Date: Thu Jul 24 2003 - 11:07:12 EDT

  • Next message: Hironori Ito: "Re: quation about automake with additional optimization"
    Hi Hiro, 
    
    Hironori Ito <hito@rcf.rhic.bnl.gov> wrote concerning
      Re: quation about automake with additional optimization [Thu, 24 Jul 2003 10:29:34 -0400] 
    ----------------------------------------------------------------------
    > Hello. 
    > 
    > I knew CXXFLAGS option can be used, but this will replace any
    > default option in brat.  On the other hand, I just want to
    > _*append*_ my option (not replacing it).  For example, I can easily
    > add my option in ROOT by editing config/Makefile.linux.  Are there
    > any easy ways for BRAT/BRAG?
    
    Yes, just do 
    
         CXXFLAGS="-march=pentium4 -msse2 -O2 -g" ./configure 
    
    The "-O2 -g" is the only thing set per default by `./configure.'.  Iff
    we needed special flags for building BRAT, then we'd put that in the
    `AM_CXXFLAGS' variable in some `Makefile.am'.  
    
    For the record: the ROOT build system sucks!  I should know - I helped
    write some of the stuff.  Also, the best way to do custom stuff in the
    ROOT build, is to make the file `root/MyConf.mk' (I think), and define
    additional stuff there, say: 
    
      #
      CXXFLAGS	:= $(CXXFLAGS) -some-crazy-option
    
      #
      # EOF
    
    For the problem at hand, check if one of the optimisation levels
    `-O<x>' includes the stuff you need, and if so, pass `./configure' the
    option  `--enable-optimization=<x>'.  Also, you should really disable
    debugging symbols too `--disable-debug' if you care about speed (takes
    up memory).   
    
    Please note, that there was (and probably still is) a problem with
    optimisation on SMP machines and ROOT code and ROOT client code.  I
    believe the symptom is sporadic SIGSEGVs. 
    
    Hope that helps. 
    
    Yours, 
    
     ___  |  Christian Holm Christensen 
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