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fo4-gc-test
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fo4-gc-test
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#!/usr/bin/perl
# Basic testing script for Bethesda's busted Papyrus VM iterative GC.
#
# Per Nukem, `struct_cleanup_v0` is the method used by the vanilla game. It
# unfortunately has a critical flaw where if the first index is to be GC'ed it
# will process that index and that index only and then return. This is due to
# its over-reliance on index positions being consistent even though the same
# function modifies the array it's operating on (and does not increment the
# working index in that case). A better approach is to guard against processing
# no more than n elements of the array (v1) rather than worrying if the current
# array index == starting index.
#
# To see an example of how the vanilla approach is problematic, run:
#
# $ fo4-gc-test --dead-chance=99 --max-cycles=100
#
# Then watch the algorithm return after the first GC-able element multiple
# times in a row until it finally finds a live element which it can skip. This
# results in the working index being advanced past the tracking index, hence
# making the while condition true and allowing it to GC multiple elements
# until either wrap-around to the tracking index or time runs out.
package fo4_gc_test;
use Getopt::Long qw(:config no_ignore_case no_auto_abbrev bundling);
use Carp qw(confess);
use Data::Dumper;
use Pod::Usage;
use strict;
use warnings FATAL => qw(all);
local $SIG{__DIE__} = \&confess;
local $Data::Dumper::Sortkeys = 1;
local $Data::Dumper::Useqq = 1;
our $VERSION = '$Id$';
my $verbose = 0;
my $method = 'struct_cleanup_v0';
my $method_tab = {
'struct_cleanup_v0' => \&struct_cleanup_v0,
'struct_cleanup_v1' => \&struct_cleanup_v1,
'struct_cleanup_v2' => \&struct_cleanup_v2,
};
sub new {
my ($class, $rc) = @_;
return bless { id => int(rand(2**32)), ref_count => $rc || 1 }, $class;
}
use Class::XSAccessor (
accessors => { map +($_, $_), qw(ref_count) }
);
# bool CleanupStructs(float TimeBudget, BSTArray<BSTSmartPointer<BSScript::Struct>>& Elements, uint32_t& NextIndexToClean)
# {
# bool didGC = false;
#
# float startTime = BSPrecisionTimer::GetTimer();
# float budget = BSPrecisionTimer::fFrequencyMS * TimeBudget;
#
# // NextIndexToClean stores the last checked entry for iterative GC purposes.
# if (NextIndexToClean >= Elements.QSize())
# NextIndexToClean = Elements.QSize() - 1;
#
# uint32_t index = NextIndexToClean;
#
# if (!Elements.QEmpty())
# {
# do
# {
# auto& element = Elements[index];
#
# if (element->RefCount == 1)
# {
# didGC = true;
# Elements.RemoveIndex(index);
#
# if (!Elements.QEmpty() && NextIndexToClean >= Elements.QSize())
# NextIndexToClean = Elements.QSize() - 1;
#
# // Note that 'index' isn't incremented when an entry is deleted. There's a chance that 'NextIndexToClean' == 'index' on the first loop.
# }
# else
# {
# index++;
# }
#
# if (index >= Elements.QSize())
# index = 0;
#
# } while (
# index != NextIndexToClean && // Break when 'index' == 'NextIndexToClean'. Refer to the previous note. This CAN exit after a single object is collected.
# !Elements.QEmpty() &&
# BSPrecisionTimer::GetTimer() - startTime <= budget);
# }
#
# NextIndexToClean = index;
# return didGC;
# }
sub struct_cleanup_v0 {
my ($elements, $index_next, %opts) = @_;
my $min_proc = $opts{'min_proc'} // 8;
my $max_proc = $opts{'max_proc'} // 32;
my $gc = 0;
if ($$index_next >= scalar @$elements) {
$$index_next = scalar @$elements - 1;
}
my $index = $$index_next;
return $gc unless (scalar @$elements);
# simulate variable time-cost within budget with a random amount of cycles
my $time_max = ($min_proc < $max_proc ? $min_proc : $max_proc)
+ ($max_proc > $min_proc ? int(rand($max_proc - $min_proc)) : 0);
do {
if ($verbose) {
printf STDERR ("size == %2d, index == %2d, index_next == %2d, time_max == %2d, will_gc == %d\n",
scalar @$elements, $index, $$index_next, $time_max, $elements->[$index]->ref_count <= 1);
}
my $elem = $elements->[$index];
if ($elem->ref_count == 1) {
splice(@$elements, $index, 1);
$elem->{'ref_count'}--;
$gc++;
if (scalar @$elements && $$index_next >= scalar @$elements) {
$$index_next = scalar @$elements - 1;
}
# do not advance index here as the array has shrunk
# and index now points to the previously next index
} else {
$index++;
}
# wrap around if necessary
if ($index >= scalar @$elements) {
$index = 0;
}
} while ($index != $$index_next && scalar @$elements && --$time_max > 0);
$$index_next = $index;
return $gc;
}
# bool CleanupStructs(float TimeBudget, BSTArray<BSTSmartPointer<BSScript::Struct>>& Elements, uint32_t& NextIndexToClean)
# {
# bool didGC = false;
#
# float startTime = BSPrecisionTimer::GetTimer();
# float budget = BSPrecisionTimer::fFrequencyMS * TimeBudget;
#
# // NextIndexToClean stores the last checked entry for iterative GC purposes. If
# // it's beyond the size of the array, reset it to the start and go from there.
# uint32_t index = (NextIndexToClean < Elements.QSize() ? NextIndexToClean : 0);
#
# // Examine no more elements than the array currently holds, regardless of position.
# // If no elements are cleaned this will not be more than a full wrap-around.
# uint32_t elem_max = Elements.QSize();
#
# while (elem_max-- && !Elements.QEmpty() && BSPrecisionTimer::GetTimer() - startTime <= budget)
# {
# auto& element = Elements[index];
#
# if (element->RefCount == 1)
# {
# Elements.RemoveIndex(index);
# didGC = true;
#
# // do not advance index here as the array has shrunk
# // and index now points to the previously next index
# }
# else
# {
# index++;
# }
#
# // wrap around if necessary
# if (index >= Elements.QSize())
# index = 0;
# }
#
# NextIndexToClean = index;
#
# return didGC;
# }
sub struct_cleanup_v1 {
my ($elements, $index_next, %opts) = @_;
my $min_proc = $opts{'min_proc'} // 8;
my $max_proc = $opts{'max_proc'} // 32;
my $gc = 0;
# if index-next is past the end of the array, reset to the start
my $index = $$index_next < scalar @$elements ? $$index_next : 0;
# simulate variable time-cost within budget with a random amount of cycles
my $time_max = ($min_proc < $max_proc ? $min_proc : $max_proc)
+ ($max_proc > $min_proc ? int(rand($max_proc - $min_proc)) : 0);
# do not process more than these many elements, regardless of index position
my $elem_max = scalar @$elements;
while ($elem_max-- && scalar @$elements && $time_max--) {
if ($verbose) {
printf STDERR ("size == %2d, index == %2d, elem_max == %2d, time_max == %2d, will_gc == %d\n",
scalar @$elements, $index, $elem_max, $time_max, $elements->[$index]->ref_count <= 1);
}
my $elem = $elements->[$index];
if ($elem->ref_count == 1) {
splice(@$elements, $index, 1);
$elem->{'ref_count'}--;
$gc++;
# do not advance index here as the array has shrunk
# and index now points to the previously next index
} else {
$index++;
}
# wrap around if necessary
if ($index >= scalar @$elements) {
$index = 0;
}
}
$$index_next = $index;
return $gc;
}
# bool CleanupStructs(float TimeBudget, BSTArray<BSTSmartPointer<BSScript::Struct>>& Elements, uint32_t& NextIndexToClean)
# {
# bool didGC = false;
#
# float startTime = BSPrecisionTimer::GetTimer();
# float budget = BSPrecisionTimer::fFrequencyMS * TimeBudget;
#
# // NextIndexToClean stores the last checked entry for iterative GC purposes. If
# // it's beyond the size of the array, reset it to the end and go backwards from there.
# uint32_t index = (NextIndexToClean < Elements.QSize() ? NextIndexToClean : Elements.QSize() - 1);
#
# // Examine no more elements than the array currently holds, regardless of position.
# // If no elements are cleaned this will not be more than a full wrap-around.
# uint32_t elem_max = Elements.QSize();
#
# while (elem_max-- && !Elements.QEmpty() && BSPrecisionTimer::GetTimer() - startTime <= budget)
# {
# auto& element = Elements[index];
#
# if (element->RefCount == 1)
# {
# Elements.RemoveIndex(index);
# didGC = true;
# }
#
# // wrap around if necessary
# if (!index--)
# index = Elements.QSize() - 1;
# }
#
# NextIndexToClean = index;
#
# return didGC;
# }
sub struct_cleanup_v2 {
my ($elements, $index_next, %opts) = @_;
my $min_proc = $opts{'min_proc'} // 8;
my $max_proc = $opts{'max_proc'} // 32;
my $gc = 0;
# if index-next is past the end of the array, reset to the end
my $index = $$index_next < scalar @$elements ? $$index_next : scalar @$elements - 1;
# simulate variable time-cost within budget with a random amount of cycles
my $time_max = ($min_proc < $max_proc ? $min_proc : $max_proc)
+ ($max_proc > $min_proc ? int(rand($max_proc - $min_proc)) : 0);
# do not process more than these many elements, regardless of index position
my $elem_max = scalar @$elements;
while ($elem_max-- && scalar @$elements && $time_max--) {
if ($verbose) {
printf STDERR ("size == %2d, index == %2d, elem_max == %2d, time_max == %2d, will_gc == %d\n",
scalar @$elements, $index, $elem_max, $time_max, $elements->[$index]->ref_count <= 1);
}
my $elem = $elements->[$index];
if ($elem->ref_count == 1) {
splice(@$elements, $index, 1);
$elem->{'ref_count'}--;
$gc++;
}
# wrap around if necessary
if (!$index--) {
$index = scalar @$elements - 1;
}
}
$$index_next = $index;
return $gc;
}
sub elements_dump {
my ($elements, $max_size, $pre, $pst, $gc) = @_;
my $element_count = scalar @$elements;
my @lout;
my $live_count = 0;
for (my $i = 0; $i < $element_count; $i++) {
push @lout, $elements->[$i]->ref_count == 1 ? '.' : '*';
$live_count++ if ($elements->[$i]->ref_count > 1);
}
my @iout = split('', ' ' x $max_size);
$iout[$pre] = '^' if (defined $pre);
$iout[$pst] = ($pst == $pre ? '>' : '$') if (defined $pst);
my @xout = split('', '0123456789' x ($max_size / 10));
printf STDERR ("%2s |%*.*s|\n", ' ', $max_size, $element_count, join('', @xout));
printf STDERR ("%2d :: |%*.*s| live: %d, dead: %d\n", $element_count, $max_size, $max_size, join('', @lout), $live_count, $element_count - $live_count);
printf STDERR ("%2d :: |%*.*s| idx: %d -> %d\n", $gc // 0, $max_size, $element_count, join('', @iout), $pre, $pst);
printf STDERR "\n";
}
sub elements_gen {
my ($max, $dead_chance) = @_;
my @tmp;
while ($max--) {
my $live = rand(1) > $dead_chance / 100 ? 1 : 0;
my $elem = __PACKAGE__->new(1 + $live);
push @tmp, $elem;
}
return @tmp;
}
sub main {
my $ret;
my $help = 0;
my $max_size = 80;
my $max_cycles = 20;
my $index_init = 0;
my $constant_fill = 0;
my $alter_scanned = 0;
my $alter_scanned_chance = 10;
my $dead_chance = 50;
my $min_proc = 8;
my $max_proc = 32;
local @ARGV = @_;
GetOptions(
'h|help' => \$help,
'verbose|v+' => \$verbose,
'max-size=i' => \$max_size,
'max-cycles=i' => \$max_cycles,
'init-index=i' => \$index_init,
'constant-fill+' => \$constant_fill,
'alter-scanned+' => \$alter_scanned,
'alter-scanned-chance=i' => \$alter_scanned_chance,
'dead-chance=i' => \$dead_chance,
'min-proc=i' => \$min_proc,
'max-proc=i' => \$max_proc,
'method=s' => \$method,
) && (!$help && ($ret = 1));
$ret || pod2usage(-verbose => 2, -noperldoc => 1, -exitval => -1);
# gc method to use
my $cb = $method_tab->{$method} || die "Unknown method";
my %cb_opts = (
min_proc => $min_proc,
max_proc => $max_proc,
);
# initial index
my $index_next = $index_init;
# initial propagation
my $elements = [ elements_gen($max_size, $dead_chance) ];
# dump initial layout
elements_dump($elements, $max_size, $index_next, $index_next, 0);
while ($max_cycles-- && grep +($_->ref_count <= 1), @$elements) {
my $index_next_pre = $index_next;
my $gc = $cb->($elements, \$index_next, %cb_opts);
if ($constant_fill) {
# fill in new objects to keep array a constant length
push @$elements, elements_gen($max_size - scalar @$elements, $dead_chance);
}
elements_dump($elements, $max_size, $index_next_pre, $index_next, $gc);
if ($alter_scanned) {
# randomly set some already scanned live objects to cleanable
for (my $i = $index_next_pre; $i < $index_next && $i < scalar @$elements; $i++) {
next if ($elements->[$i]->ref_count <= 1);
next if (rand(1) > $alter_scanned_chance / 100);
$elements->[$i]{'ref_count'}--;
}
}
}
return 1;
}
exit !main(@ARGV) unless (caller);
__END__