Re: GMAKE speed ups.

[Paul D. Smith]

%% Bijal Shah <address@hidden> writes:

  bs> Part1:
  bs> ======
  bs> Add the following rule to the makefile.

  bs>   .SUFFIXES:

  bs> This resulted improvement to 2.6 seconds for the same GMAKE invokation.

  bs> Part2:
  bs> ======

  bs> Explicitly disable the built-in rules - there isn't an easy way to
  bs> do this, but its worth it. These can be found with "gmake -p", but
  bs> here is the full list anyway:

  bs> %: %.c

  bs> (%): %

  bs> %.out: %

  bs> %.c: %.w %.ch

  bs> %.tex: %.w %.ch

  bs> %:: %,v

  bs> %:: RCS/%,v

  bs> %:: RCS/%

  bs> %:: s.%

  bs> %:: SCCS/s.%

None of these below should be in your makefile.  The .SUFFIXES: will
turn all of these off.

  bs> .c:
  bs> .texinfo.info:
  bs> .mod.o:
  bs> .c.o:
  bs> .s:
  bs> .txinfo.dvi:
  bs> .y.c:
  bs> .web.tex:
  bs> .s.o:
  bs> .F.f:
  bs> .web.p:
  bs> .F:
  bs> .cc.o:
  bs> .S.s:
  bs> .def.sym:
  bs> .F.o:
  bs> .f:
  bs> .y.ln:
  bs> .texi.dvi:
  bs> .texinfo.dvi:
  bs> .p.o:
  bs> .r.f:
  bs> .w.tex:
  bs> .txinfo.info:
  bs> .o:
  bs> .c.ln:
  bs> .l.r:
  bs> .r.o:
  bs> .C.o:
  bs> .p:
  bs> .l.c:
  bs> .sh:
  bs> .cc:
  bs> .f.o:
  bs> .texi.info:
  bs> .cpp.o:
  bs> .l.ln:
  bs> .S.o:
  bs> .tex.dvi:
  bs> .r:
  bs> .mod:
  bs> .C:
  bs> .S:
  bs> .w.c:
  bs> .cpp:

  bs> This improved the performance further to .6 seconds. I did some
  bs> basic analysis to figure out what was taking the most time out of
  bs> all these rules and it has proven to be the :: rules for RCS and
  bs> SCCS updating. Even with a few files, the checks that these rules
  bs> invoked added significantly to overall processing time.

That's because those rules are "match anything" rules; that is, the left
hand pattern is "%" with no suffix, etc.  That means that make will
_always_ consider that rule when looking for an implicit way to build
targets, no matter what the filename is.

The other pattern rules, like 

-- 
-------------------------------------------------------------------------------
 Paul D. Smith <address@hidden>          Find some GNU make tips at:
 http://www.gnu.org                      http://make.paulandlesley.org
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist