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hypersearch
executable file
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hypersearch
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#! /usr/bin/env perl
use warnings;
use strict;
# two parameters:
# cmd - a command or reference to an array of command + arguments
# timeout - number of seconds to wait (0 = forever)
# returns:
# cmd exit status (-1 if timed out)
# cmd results (STDERR and STDOUT merged into an array ref)
sub ExecCmd {
my $cmd = shift || return(0, []);
my $timeout = shift || 0;
# opening a pipe creates a forked process
my $pid = open(my $pipe, '-|');
return(-1, "Can't fork: $!") unless defined $pid;
if ($pid) {
# this code is running in the parent process
my @result = ();
if ($timeout) {
my $failed = 1;
eval {
# set a signal to die if the timeout is reached
local $SIG{ALRM} = sub { die "alarm\n" };
alarm $timeout;
@result = <$pipe>;
alarm 0;
$failed = 0;
};
return(-1, ['command timeout', @result]) if $failed;
}
else {
while (<$pipe>)
{
push @result, $_;
print STDERR ".";
}
}
close($pipe);
# return exit status, command output
return ($? >> 8), \@result;
}
# this code is running in the forked child process
{ # skip warnings in this block
no warnings;
# redirect STDERR to STDOUT
open(STDERR, '>&STDOUT');
# exec transfers control of the process
# to the command
ref($cmd) eq 'ARRAY' ? exec(@$cmd) : exec($cmd);
}
# this code will not execute unless exec fails!
print "Can't exec @$cmd: $!";
exit 1;
}
sub evaluate ($)
{
my ($rate) = @_;
my $nicerate = sprintf ("%.5g", $rate);
print STDERR "trying $nicerate ";
my @command = @ARGV;
foreach my $c (@command) { $c =~ s/\%/$rate/g; };
my ($status, $rv) = ExecCmd \@command;
die "subprocess invocation failed: $!" if $status;
my $loss;
foreach my $line (@$rv)
{
next unless $line =~ m%average loss = ([0-9\.]+)%;
$loss = $1;
}
die "failed to parse average loss from vw output: ", join "", @$rv
unless defined ($loss);
warn " $loss\n";
return $loss;
}
sub argmin3 ($$$$$$)
{
my ($a, $fa, $b, $fb, $c, $fc) = @_;
if ($fa < $fb)
{
return $fa < $fc ? ($a, $fa) : ($c, $fc);
}
else
{
return $fb < $fc ? ($b, $fb) : ($c, $fc);
}
}
my $lb = shift @ARGV;
my $ub = shift @ARGV;
my $flb = evaluate ($lb);
my $fub = evaluate ($ub);
my $tol = 1e-2;
my $phi = (1.0 + sqrt (5.0)) / 2.0;
my $resphi = 2.0 - $phi;
my $mid = $lb + $resphi * ($ub - $lb);
my $fmid = evaluate ($mid);
while (abs ($ub - $lb) > $tol * abs ($ub + $lb))
{
my $x = ($ub - $mid > $mid - $lb) ? $mid + $resphi * ($ub - $mid)
: $mid - $resphi * ($mid - $lb);
my $fx = evaluate ($x);
if ($fx < $fmid)
{
if ($ub - $mid > $mid - $lb)
{
$lb = $mid; $mid = $x;
$flb = $fmid; $fmid = $fx;
}
else
{
$ub = $mid; $mid = $x;
$fub = $fmid; $fmid = $fx;
}
}
else
{
if ($ub - $mid > $mid - $lb)
{
$ub = $x;
$fub = $fx;
}
else
{
$lb = $x;
$flb = $fx;
}
}
}
my ($best, $fbest) = argmin3 ($lb, $flb, $mid, $fmid, $ub, $fub);
print "$best\t$fbest\n";