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gator 1 Introduction Mercury provides a large number of compile-time options that enable or disable optimisations to the code being generated. It can be difficult to determine which ones to apply, especially since different options may work better with different programs or different inputs. This program attempts to find the optimal set of optimisation flags to be passed to the compiler. It works using a genetic algorithm; see the following URLs for details on how genetic algorithms work: <http://en.wikipedia.org/wiki/Genetic_algorithm> <http://www.cs.cmu.edu/Groups/AI/html/faqs/ai/genetic/top.html> The program is invoked using the gator script. It may be useful (if something goes wrong) to turn on the verbose flag and pipe the output to a file: ./gator -v 2>&1 | tee gator.out The program stores its output in the directory generations. Each generation has its own subdirectory within generations. For example, information about the first generation is stored in generations/1. There are a number of files in each of these directories. The most useful one is the file "ladder". This file contains a table listing all of the individuals in a generation. Each individual is given a number, between 1 and the size of its generation, in the first column of the table. The second column contains the "fitness" of an individual. The third column contains the "genotype" of an individual, which is the list of compiler options that are passed to the compiler. By default, gator is configured to optimise a simple "hello world" program written in Mercury. The following sections describe how to configure gator to test different programs, including those using different programming languages and compilers. 2 Configuring for your network gator has been written to utilise multiple hosts on a network. In order to configure gator for your network, the gator.conf file needs to contain information about all the hosts to be used. Configuring gator.conf involves defining a set of variables and assigning them values. The syntax is the same as defining shell variables in /bin/sh. The following variable must be defined: num_hosts: the number of hosts available for benchmarking. This may include the host from which gator is being run, if it is also being used to run the benchmarks. For each host, the following variables need to be defined, where $i is an integer between 1 and $num_hosts. host$i: the name of the host we are connecting to. This is passed as a command-line argument to ssh(1). Make sure you have a copy of the host's SSH public key in your cache before you run gator. workspace$i: the path to a directory containing gator. Note that nothing is written to this directory, it is just used to access the dotime and evaluate.conf files from a remote host. It can be the same on all hosts, as long as this directory is also mounted on all of the remote machines. benchmarks$i: similar to workspace$i, except it contains the benchmarks directory from CVS. Note that each host must have its own benchmarks directory. path$i: the path to the directory containing the compiler. This is pre-pended to $PATH in the evaluate script. The hosts in gator.conf are accessed using ssh(1) and ssh-agent(1). It is necessary to have SSH keys set up on each of these hosts. See the following URL for details on how to use ssh-agent(1): <http://mah.everybody.org/docs/ssh> As an example, suppose we are setting up gator to run on a network containing two hosts named "jupiter" and "saturn". num_hosts=2 host1=jupiter workspace1=$HOME/mercury/extras/gator benchmarks1=/home/jupiter/samrith/mercury/samples path1=/home/jupiter/public/mercury-latest/i686-pc-linux-gnu/bin host2=saturn workspace2=$HOME/mercury/extras/gator benchmarks2=/home/saturn/samrith/mercury/samples path2=/home/saturn/public/mercury-latest/i686-pc-linux-gnu/bin In this example, $workspace1 and $workspace2 are both the same path, and are on the same NFS-mounted filesystem. All of the workspaces may be on the same filesystem, although they don't have to be. However, the benchmark directories must be separate directories, so that separate builds can be done on each host. In this example, $benchmarks1 and $benchmarks2 are located on their host's local filesystems. 3 Configuring for your software The evaluate.conf file allows the user to change the benchmarking information gathered by gator. This is useful if gator is being used to test different compilers, and/or different programs. The syntax is identical to that of gator.conf (see section 2). The following variable must be defined: num_progs: the number of programs used for benchmarking. Note that if the number of programs is changed, the way that "fitness" is evaluated will need to be changed. This should be done by defining a new set of "Weightings" in evolve.conf (see section 4). For each program, the following variables need to be defined, where $i is an integer between 1 and $num_progs. prog$i: the full path to the executable for the program (which may not yet be built). This may or may not be contained under "$benchmarks" (see section 2). clean$i: the command used to completely clean up the source directory (e.g., "make realclean"). compile$i: the command used to compile the program. Note that you may assume there is a $flags shell variable which gives the optimization flags passed to the compiler. run$i: the command used to run the program. For example, suppose we want to change the program being optimised. The new program is in "benchmarks/progs/ray/proj.m", rather than "mercury/samples/hello.m". The first thing that needs to be done is to copy the program's source code to any one of the hosts. gator will then find it and copy it to the other hosts. Then, the gator.conf file needs to be modified. The new file is similar to the example given above, except that the $benchmarks1 and $benchmarks2 directories are different: benchmarks1=/home/jupiter/samrith/benchmarks benchmarks2=/home/saturn/samrith/benchmarks The evaluate.conf file would look like this: num_progs=1 prog1="$benchmarks"/progs/ray/proj clean1="mmc --make proj.realclean; rm -rf Mercury" compile1="mmc --make -O0 $flags proj" run1="./proj -f 100 -S -s 0.4 2 -a 0.1 dh.scene 140 140 0 0 0 >dh.ppm" The example above gives just one Mercury program. The default evolve.conf file is set up for just one Mercury program, so if more programs or different compilers are used, it is necessary to modify evolve.conf (see section 4 for details). 4 Configuring parameters for the genetic operators If the intention is to, for example, optimise for space instead of time, then it may be necessary to modify certain parameters of the genetic operators. This can be achieved by modifying the evolve.conf file, which allows the user to tweak the parameters of certain genetic operators including the fitness operator and the mutation operator. The syntax of evolve.conf is a bit different to that of gator.conf and evaluate.conf. Currently, evolve.conf must contain two terms that can be read by io.read/3. The first term contains the "Weightings" used by phenotype.fitness/2. This parameter is coupled with the number of programs being tested (see section 3 on evaluate.conf). For each program, there are three measurements taken by the software: the compile time, the executable size and the time taken to run the executable. Because of this, the list must be of length $num_progs * 3. These next examples cause gator to search for a set of flags that will minimize the compilation time for five programs, [ 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]. weight compile times and run times equally, [ 0.5, 0.5, 0.5, 0.5, 0.5, 0.0, 0.0, 0.0, 0.0, 0.0, 0.5, 0.5, 0.5, 0.5, 0.5 ]. or optimise for space, while ignoring the second program in the set. [ 0.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0 ]. The second term contains a complete list of flags that can be passed to the compiler. This is used by genotype.mutation/5, which toggles a random flag in an individual's genotype. Suppose the evaluate.conf file (see section 3 for details) specifies two programs, both of which are compiled with gcc(1). In this case, the first term would need to be a list of length $num_progs * 3 = 2 * 3 = 6. The second term would need to contain a list of gcc optimisation options, rather than mmc options. The following example works for gcc 3.3.5. [ 0.5, 0.5, 0.0, 0.0, 1.0, 1.0 ]. [ "-fbranch-probabilities", "-fcaller-saves", "-fcprop-registers", "-fcse-follow-jumps", "-fcse-skip-blocks", "-fdata-sections", "-fdelayed-branch", "-fdelete-null-pointer-checks", "-fexpensive-optimizations", "-ffast-math", "-ffloat-store", "-fforce-addr", "-fforce-mem", "-ffunction-sections", "-fgcse", "-fgcse-lm", "-fgcse-sm", "-floop-optimize", "-fcrossjumping", "-fif-conversion", "-fif-conversion2", "-finline-functions", "-fkeep-inline-functions", "-fkeep-static-consts", "-fmerge-constants", "-fmerge-all-constants", "-fmove-all-movables", "-fnew-ra", "-fno-branch-count-reg", "-fno-default-inline", "-fno-defer-pop", "-fno-function-cse", "-fno-guess-branch-probability", "-fno-inline", "-fno-math-errno", "-fno-peephole", "-fno-peephole2", "-funsafe-math-optimizations", "-ffinite-math-only", "-fno-trapping-math", "-fno-zero-initialized-in-bss", "-fomit-frame-pointer", "-foptimize-register-move", "-foptimize-sibling-calls", "-fprefetch-loop-arrays", "-freduce-all-givs", "-fregmove", "-frename-registers", "-freorder-blocks", "-freorder-functions", "-frerun-cse-after-loop", "-frerun-loop-opt", "-fschedule-insns", "-fschedule-insns2", "-fno-sched-interblock", "-fno-sched-spec", "-fsched-spec-load", "-fsched-spec-load-dangerous", "-fsignaling-nans", "-fsingle-precision-constant", "-fssa", "-fssa-ccp", "-fssa-dce", "-fstrength-reduce", "-fstrict-aliasing", "-ftracer", "-fthread-jumps", "-funroll-all-loops", "-funroll-loops" ]. 5 Further modifying the genetic operators The genetic operators themselves can be modified directly. They are implemented in the following functions/predicates: phenotype.fitness/2 phenotype.selection/6 genotype.crossover/6 genotype.mutation/5