Pluto

OVERVIEW

Please see http://pluto-compiler.sourceforge.net.

This package includes both the tool pluto and libpluto. The pluto tool is a source-to-source transformer meant to be run via the polycc script, libpluto provides a thread-safe library interface.

LICENSE

Pluto and libpluto are available under the MIT LICENSE. Please see the file LICENSE in the top-level directory for more details.

INSTALLING PLUTO

PREREQUISITES

A Linux distribution. Pluto has been tested on x86 and x86-64 machines running Fedora, Ubuntu, and CentOS.

• In order to use the development version from Pluto's git repository, automatic build system tools, including autoconf, automake, and libtool are needed.

• LLVM/Clang 2.9 or higher until 14.x (14.x recommended, 11.x, 12.x tested to work as well), along with its development/header files, is needed for the pet submodule. These packages are available in standard distribution repositories or could be installed by building LLVM and Clang from sources. See pet/README for additional detail. On most modern distributions, these can be installed from the repositories.

  Example:

  # On an Ubuntu.
  sudo apt install -y llvm-14-dev libclang-14-dev
  # On a Fedora.
  sudo dnf -y install llvm14-devel clang14-devel

• LLVM FileCheck is used for Pluto's test suite. (On a Fedora, this is part of the 'llvm' package.)

• GMP (GNU multi precision arithmetic library) is needed by ISL (one of the included libraries). If it's not already on your system, it can be installed easily with, for eg., sudo yum -y install gmp gmp-devel on a Fedora (sudo apt-get install libgmp3-dev or something similar on an Ubuntu).

Pluto includes all polyhedral libraries that it depends on. See pet/README for pet's pre-requisites.

BUILDING PLUTO

Stable release:

$ tar zxvf pluto-0.11.4.tar.gz
$ cd pluto-0.11.4/
$ ./configure [--with-clang-prefix=<clang install location>]
$ make
$ make test

configure can be provided --with-isl-prefix=<isl install location> to build with another isl, otherwise the bundled isl is used.

Development version from Git:

git clone [email protected]:bondhugula/pluto.git
cd pluto/
git submodule init
git submodule update
./autogen.sh
./configure [--enable-debug] [--with-clang-prefix=<clang headers/libs location>]
# Example: on an Ubuntu: --with-clang-prefix=/usr/lib/llvm-14, on a Fedora, 
# typically, it's /usr/lib64/llvm14.
make
make check-pluto

• Use --with-clang-prefix=<location> to point to the specific clang to build with.

• Use --with-isl-prefix=<isl install location> to compile and link with an already installed isl. By default, the version of isl bundled with Pluto will be used.

polycc is the wrapper script around src/pluto (core transformer) and all other components. polycc runs all of these in sequence on an input C program (with the section to parallelize/optimize marked) and is what a user should use on input. Output generated is OpenMP parallel C code that can be readily compiled and run on shared-memory parallel machines like general-purpose multicores. libpluto.{so,a} is also built and can be found in src/.libs/. make install will install it.

TRYING A NEW EXAMPLE

• Use #pragma scop and #pragma endscop around the section of code you want to parallelize/optimize.

• Then, just run ./polycc <C source file>.

  The transformation is also printed out, and test.par.c will have the parallelized code. If you want to see intermediate files, like the .cloog file generated (.opt.cloog, .tiled.cloog, or .par.cloog depending on command-line options provided), use --debug on command line.

• Tile sizes can be specified in a file tile.sizes, otherwise default sizes will be set. See doc/DOC.txt on how to specify the sizes.

To run a good number of experiments on a code, it is best to use the setup created for example codes in the examples/ directory. If you do not have ICC (Intel C compiler), uncomment line 9 and comment line 8 of examples/common.mk to use GCC.

• Just copy one of the sample directories in examples/, edit Makefile (SRC = ).

• do a make (this will build all executables; orig is the original code compiled with the native compiler, tiled is the tiled code, par is the OpenMP parallelized + locality optimized code. One could do make <target> where target can be orig, orig_par, opt, tiled, par, pipepar, etc (see examples/common.mk for full list).

• make check-pluto to test for correctness, make perf to compare performance.

COMMAND-LINE OPTIONS

Run

./polycc -h

or see documentation (doc/DOC.txt) for details.

TRYING ANY INCLUDED EXAMPLE CODE

Let's say we are trying the 2-d gauss seidel kernel. In examples/seidel, do make par; this will generate seidel.par.c from seidel.c and also compile it to generate par. Likewise, make tiled for tiled and make orig for orig.

cd examples/seidel

seidel.c: This is the original code (the kernel in this code is extracted). orig is the corresponding executable when compiled with the native compiler (gcc or icc for eg.) with optimization flags, orig_par with the native compiler's auto-parallelization enabled.

seidel.opt.c: This is the transformed code without tiling (this is of not much use, except for seeing benefits of fusion in some cases). opt is the corresponding executable.

seidel.tiled.c: This is Pluto generated code optimized for locality with tiling and other transformations, but not not parallelized - this should be used for sequential execution. tiled is the corresponding executable.

seidel.par.c: This is Pluto parallelized code optimized for locality and parallelism with tiling and other transformations. This code has OpenMP pragmas. par is the corresponding executable.

• To change any of the flags used for an example, edit the top section of examples/common.mk or the Makefile in the example directory

• To manually specify tile sizes, create tile.sizes; see examples/matmul/ for example or doc/DOC.txt for more information on setting tile sizes.

The executables already have timers; you just have to run them and that will print execution time for the core part of the computation as well.

To run the Pluto parallelized version:

OMP_NUM_THREADS=4 ./par

To run native compiler optimized/auto-parallelized version:

OMP_NUM_THREADS=4 ./orig_par

To run the original unparallelized code:

./orig

To run the locality optimized version generated by Pluto:

./tiled

make clean in the particular example's directory removes all executables as well as generated codes.

To launch a complete verification that compares output of tiled, par with orig for all examples, in examples/, run make check-pluto.

[examples/ ]$ make check-pluto

MORE INFORMATION

• See doc/DOC.txt for an overview of the system and details on all command-line options.

• For specifying custom tile sizes through tile.sizes file, see doc/DOC.txt.

• For specifying custom fusion structure through .fst file, see doc/DOC.txt.

BUGS AND ISSUES

Please report bugs and issues at https://github.com/bondhugula/pluto/issues.

For questions and general discussion, please email [email protected] after joining the group: https://groups.google.com/g/pluto-development.