From: Vsevolod Stakhov <vsevolod@highsecure.ru>
Date: Sat, 15 Oct 2016 12:20:29 +0000 (+0100)
Subject: [Feature] Try to improve normalization function for bayes
X-Git-Tag: 1.4.0~259
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a903f7be21746c3a803d0a47dad4c0716584eaa7;p=thirdparty%2Frspamd.git

[Feature] Try to improve normalization function for bayes
---

diff --git a/src/libutil/util.c b/src/libutil/util.c
index 5380d8c944..d1332d5047 100644
--- a/src/libutil/util.c
+++ b/src/libutil/util.c
@@ -2549,17 +2549,16 @@ rspamd_shmem_xmap (const char *fname, guint mode,
  * C = -7
  * D = 3
  * y = 32(x - 0.5)^4 - 6(x - 0.5)^3 - 7(x - 0.5)^2 + 3(x - 0.5)
+ *
+ * New approach:
+ * y = ((x - bias)*2)^8
  */
 gdouble
 rspamd_normalize_probability (gdouble x, gdouble bias)
 {
-	const gdouble a = 32, b = -6, c = -7, d = 3;
-	gdouble xx, x2, x3, x4;
+	gdouble xx;
 
-	xx = x - bias;
-	x2 = xx * xx;
-	x3 = x2 * xx;
-	x4 = x3 * xx;
+	xx = (x - bias) * 2.0;
 
-	return a*x4 + b*x3 + c*x2 + d*xx;
+	return pow (xx, 8);
 }
diff --git a/src/lua/lua_util.c b/src/lua/lua_util.c
index cb24cb983b..8aec3a88d8 100644
--- a/src/lua/lua_util.c
+++ b/src/lua/lua_util.c
@@ -352,6 +352,16 @@ LUA_FUNCTION_DEF (util, zstd_compress);
  */
 LUA_FUNCTION_DEF (util, zstd_decompress);
 
+/***
+ * @function util.normalize_prob(prob, [bias = 0.5])
+ * Normalize probabilities using polynom
+ *
+ * @param {number} prob probability param
+ * @param {number} bias number to subtract for making the final sollution
+ * @return {number} normalized number
+ */
+LUA_FUNCTION_DEF (util, normalize_prob);
+
 /***
  * @function util.pack(fmt, ...)
  *
@@ -463,6 +473,7 @@ static const struct luaL_reg utillib_f[] = {
 	LUA_INTERFACE_DEF (util, random_hex),
 	LUA_INTERFACE_DEF (util, zstd_compress),
 	LUA_INTERFACE_DEF (util, zstd_decompress),
+	LUA_INTERFACE_DEF (util, normalize_prob),
 	LUA_INTERFACE_DEF (util, pack),
 	LUA_INTERFACE_DEF (util, unpack),
 	LUA_INTERFACE_DEF (util, packsize),
@@ -1724,6 +1735,23 @@ lua_util_zstd_decompress (lua_State *L)
 	return 2;
 }
 
+static gint
+lua_util_normalize_prob (lua_State *L)
+{
+	gdouble x, bias = 0.5;
+
+	x = lua_tonumber (L, 1);
+
+	if (lua_type (L, 2) == LUA_TNUMBER) {
+		bias = lua_tonumber (L, 2);
+	}
+
+	lua_pushnumber (L, rspamd_normalize_probability (x, bias));
+
+	return 1;
+}
+
+
 /* Backport from Lua 5.3 */
 
 /******************************************************************************