What's new?

April 29th 2009: Irregular extensions of the Polyhedral Model including the irCLooG prototype are available here.

April 21st 2009: GCC 4.4.0 has been published today with the GRAPHITE polyhedral framework! It uses a CLooG version, CLooG/PPL, by Sebastian Pop that relies on the PPL instead of the PolyLib (because of licensing problems).

October 28th 2008: New mailing lists for CLooG are now open, decoupled from PolyLib. See the Docs Section.

September 2nd 2008: The polyhedral framework of GCC, GRAPHITE, has been merged to GCC 4.4 trunk! It uses a CLooG version, CLooG/PPL, by Sebastian Pop that relies on the PPL instead of the PolyLib (because of licensing problems).

June 9th 2008: TWO research works using CLooG are presented today at the most prestigeous conference on compilation, ACM PLDI. Bondhugula et al. presents a practical automatic parallelization and locality optimization system. Pouchet et al. presents iterative compilation based on multidimensional schedules.

What's CLooG?

CLooG is a free software and library to generate code for scanning Z-polyhedra. That is, it finds a code (e.g. in C, FORTRAN...) that reaches each integral point of one or more parameterized polyhedra. CLooG has been originally written to solve the code generation problem for optimizing compilers based on the polytope model. Nevertheless it is used now in various area e.g. to build control automata for high-level synthesis or to find the best polynomial approximation of a function. CLooG may help in any situation where scanning polyhedra matters. While the user has full control on generated code quality, CLooG is designed to avoid control overhead and to produce a very effective code.
Polyhedral Domains to Scan Scanning Code Optimized for Size Scanning Code Optimized for Control
  for (i=1;i<=8;i++) {
    for (j=i-1;j<=7;j++) {
      S1(i,j);
    }
    if ((i>=2)&&(i<=6)) {
      for (j=0;j<=4;j++) {
        S2(i,j);
      }
    }
  }
  for (j=0;j<=7;j++) {
    S1(1,j);
  }
  for (i=2;i<=5;i++) {
    for (j=0;j<=i-2;j++) {
      S2(i,j) ;
    }
    for (j=i-1;j<=4;j++) {
      S1(i,j);
      S2(i,j) ;
    }
    for (j=5;j<=7;j++) {
      S1(i,j);
    }
  }
  for (j=0;j<=4;j++) {
    S2(6,j) ;
  }
  for (j=5;j<=7;j++) {
    S1(6,j);
  }
  for (i=7;i<=8;i++) {
    for (j=i-1;j<=7;j++) {
      S1(i,j);
    }
  }
CLooG stands for Chunky Loop Generator: it is a part of the Chunky project, a research tool for data locality improvement. It is designed to be also the back-end of automatic parallelizers like LooPo. Thus it is very 'compilable code oriented' and provides powerful program transformation facilities. Mainly, it allows the user to specify very general schedules, e.g. where unimodularity or invertibility doesn't matter.

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