commit ceed6130e8904712d012ce865956fcd32105c322
parent 3b6a4d8fc5abcb95190fb0208dacb0f96b6c44cb
Author: Ryan Wolf <rwolf@borderstylo.com>
Date: Wed, 3 Mar 2010 02:21:02 -0800
fixed merge conflicts
Diffstat:
| M | resera.pl | | | 143 | +++++++++++++++++++++++++++++++++++++++++-------------------------------------- |
1 file changed, 75 insertions(+), 68 deletions(-)
diff --git a/resera.pl b/resera.pl
@@ -7,82 +7,89 @@
use strict;
use warnings;
-# default taken from http://en.wikipedia.org/wiki/Prisoner%27s_dilemma
-my $grid = [
- [[3, 3], [0, 5]],
- [[5, 0], [1, 1]]
-];
-if (scalar @ARGV == 8) {
- $grid = [
- [[$ARGV[0], $ARGV[1]], [$ARGV[2], $ARGV[3]]],
- [[$ARGV[4], $ARGV[5]], [$ARGV[6], $ARGV[7]]]
- ];
-}
-
-my $pm = " Choice 1 | Choice 2\n" .
- " --------------------\n" .
- "Choice 1 | %3d, %3d | %3d, %3d\n" .
- "Choice 2 | %3d, %3d | %3d, %3d\n\n";
-printf(
- $pm,
- $grid->[0][0][0],
- $grid->[0][0][1],
- $grid->[0][1][0],
- $grid->[0][1][1],
- $grid->[1][0][0],
- $grid->[1][0][1],
- $grid->[1][1][0],
- $grid->[1][1][1]
-);
+my $iterations = 100000;
-my $m = [
- $grid->[0][0][0] - $grid->[0][1][0] - $grid->[1][0][0] + $grid->[1][1][0],
- $grid->[0][0][1] - $grid->[0][1][1] - $grid->[1][0][1] + $grid->[1][1][1]
+my $frequencies = [
+ [0, 0],
+ [0, 0]
];
-my $b = [
- $grid->[1][0][0] - $grid->[1][1][0],
- $grid->[1][0][1] - $grid->[1][1][1]
+# default taken from http://en.wikipedia.org/wiki/Prisoner%27s_dilemma
+my $payoff_matrices = [
+ [
+ [3, 0],
+ [5, 1]
+ ],
+ [
+ [3, 0],
+ [5, 1]
+ ]
];
-my $choices = [[0,0], [0,0]];
-
-my $iterations = 100000;
-
-for (my $n = 0; $n < $iterations; $n++) {
- my $this_choice = choice($choices, $m, $b);
- $choices->[0][$this_choice->[0]]++;
- $choices->[1][$this_choice->[1]]++;
+# also takes command line arguments
+if (scalar @ARGV == 8) {
+ $payoff_matrices->[0] = [
+ [$ARGV[0], $ARGV[2]],
+ [$ARGV[4], $ARGV[6]]
+ ];
+ $payoff_matrices->[1] = [
+ [$ARGV[1], $ARGV[5]],
+ [$ARGV[3], $ARGV[7]]
+ ];
}
-printf("Player Column:\t(%.0f%%, %.0f%%)\n",
- ($choices->[0][0] / $iterations) * 100,
- ($choices->[0][1] / $iterations) * 100);
-printf("Player Row:\t(%.0f%%, %.0f%%)\n",
- ($choices->[1][0] / $iterations) * 100,
- ($choices->[1][1] / $iterations) * 100);
-
-sub p_of_first_choice {
- my ($n_chose_first, $n_chose_second) = @_;
- my $total_choices = $n_chose_first + $n_chose_second;
- if ($total_choices == 0) {
- return .5;
+for (my $i = 0; $i < $iterations; $i++) {
+ # players must choose simultaneously--don't update the frequencies in loop
+ my $choices = [undef, undef];
+ foreach my $player (0, 1) {
+ # find the probability the other player will choose the first option
+ my $other_player = ($player + 1) % 2;
+ my $frequency = $frequencies->[$other_player];
+ my $chose_first = $frequency->[0];
+ my $total_choices = $chose_first + $frequency->[1];
+ my $p = .5;
+ unless ($total_choices == 0) {
+ $p = $chose_first / $total_choices;
+ }
+ # find the expected value of each option
+ # we'll skip the /2, since we're comparing them
+ my $pm = $payoff_matrices->[$player];
+ my $first_choice_ev = $p * $pm->[0][0] + (1 - $p) * $pm->[0][1];
+ my $second_choice_ev = $p * $pm->[1][0] + (1 - $p) * $pm->[1][1];
+ # pick the choice with the highest ev, or choose at random if they tie
+ if ($first_choice_ev != $second_choice_ev) {
+ $choices->[$player] = ($first_choice_ev > $second_choice_ev) ? 0 : 1;
+ }
+ else {
+ $choices->[$player] = int(rand() + .5);
+ }
+ }
+ # update frequencies to reflect this round
+ foreach my $player (0, 1) {
+ $frequencies->[$player][$choices->[$player]]++;
}
- return $n_chose_first / $total_choices;
}
-sub choice {
- my ($choices, $b, $m) = @_;
- my $this_choice = [undef,undef];
- foreach my $player (0,1) {
- my $o = ($player + 1) % 2;
- my $other_p = p_of_first_choice($choices->[$o][0], $choices->[$o][1]);
- my $slope = $m->[$player]*$other_p + $b->[$player];
- if ($slope == 0) {
- $this_choice->[$player] = int(rand() + .5);
- next;
- }
- $this_choice->[$player] = ($slope > 0) ? 0 : 1;
- }
- return $this_choice;
+my $pm = " Column 1 | Column 2\n" .
+ " ---------------------\n" .
+ "Row 1 | %3d, %3d | %3d, %3d\n" .
+ "Row 2 | %3d, %3d | %3d, %3d\n\n";
+printf(
+ $pm,
+ $payoff_matrices->[0][0][0],
+ $payoff_matrices->[1][0][0],
+ $payoff_matrices->[0][0][1],
+ $payoff_matrices->[1][1][0],
+ $payoff_matrices->[0][1][0],
+ $payoff_matrices->[1][0][1],
+ $payoff_matrices->[0][1][1],
+ $payoff_matrices->[1][1][1],
+);
+foreach my $player (0, 1) {
+ printf(
+ "Player %d: (%.3f%%, %.3f%%)\n",
+ $player,
+ ($frequencies->[$player][0] / $iterations) * 100,
+ ($frequencies->[$player][1] / $iterations) * 100
+ );
}
