Re: [gnugo-devel] Patch: improve separation of similarly-valued moves

[Evan Daniel]

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Paul Pogonyshev wrote:
| Here we are.
|
| - new function compute_move_probabilities() in `value_moves.c'
| - new GTP command `move_probabilities'
|
| It would be nice if anyone made use of this in a test suite.  You
| will likely have to implement more GTP commands (or change the one
| I added).

- - new GTP command 'move_uncertainty'

This patch adds the command move_uncertainty, which returns the
uncertainty of the move, in bits.  This has the convenient property that
the uncertainty across many moves can be calculated individually per
move, and then added together to get a meaningful result.

Note that for both Paul's move_probabilities command and
move_uncertainty, you must execute some form of genmove command
immediately prior in order to set up the move values.  Should this be
changed?

Now, a question about my patch...  I included math.h in play_gtp.c, to
get the log2 function.  Are there any objections to this?
Unfortunately, it doesn't seem to work on my system.  I get:

play_gtp.c: In function `gtp_move_uncertainty':
play_gtp.c:3782: warning: implicit declaration of function `log2f'

Am I doing something wrong, or is my system messed up in some strange
manner?

Thanks

Evan Daniel

(Thunderbird seems to want to wrap lines, so I've attached the patch.
I'll look into it, but let me know if that causes a problem for now.)
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diff -u interface/play_gtp.c interface/play_gtp.c
--- interface/play_gtp.c        20 Apr 2004 15:34:30 -0000
+++ interface/play_gtp.c        20 Apr 2004 16:26:24 -0000
@@ -26,6 +26,7 @@
 #include <assert.h>
 #include <ctype.h>
 #include <string.h>
+#include <math.h>
 
 #include "interface.h"
 #include "liberty.h"
@@ -136,6 +137,7 @@
 DECLARE(gtp_move_influence);
 DECLARE(gtp_move_probabilities);
 DECLARE(gtp_move_reasons);
+DECLARE(gtp_move_uncertainty);
 DECLARE(gtp_name);
 DECLARE(gtp_owl_attack);
 DECLARE(gtp_owl_connection_defends);
@@ -275,6 +277,7 @@
   {"move_influence",          gtp_move_influence},
   {"move_probabilities",      gtp_move_probabilities},
   {"move_reasons",            gtp_move_reasons},
+  {"move_uncertainty",        gtp_move_uncertainty},
   {"name",                    gtp_name},
   {"new_score",               gtp_estimate_score},
   {"orientation",            gtp_set_orientation},
@@ -3764,2 +3767,25 @@
 
+static int
+gtp_move_uncertainty(char *s)
+{
+  float probabilities[BOARDMAX];
+  int pos;
+  float uncertainty = 0.0;
+
+  UNUSED(s);
+
+  compute_move_probabilities(probabilities);
+
+  gtp_start_response(GTP_SUCCESS);
+  for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
+    if (ON_BOARD(pos) && probabilities[pos] > 0.0) {
+      uncertainty += -1 * probabilities[pos] * log2f(probabilities[pos]);
+    }
+  }
+
+  gtp_printf("%.4f\n\n", uncertainty);
+
+  return GTP_OK;
+}
+