commit 82e5883: [Feature] Neural: Allow to balance FP/FN for the network

[Vsevolod Stakhov]

Author: Vsevolod Stakhov
Date: 2021-04-29 19:41:03 +0100
URL: https://github.com/rspamd/rspamd/commit/82e588390a7f0dc000e74497cfb84e25dcbfafe5 (HEAD -> master)

[Feature] Neural: Allow to balance FP/FN for the network

---
 lualib/plugins/neural.lua  |  3 +++
 src/plugins/lua/neural.lua | 18 ++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lualib/plugins/neural.lua b/lualib/plugins/neural.lua
index c35fc0eeb..f0d5cf582 100644
--- a/lualib/plugins/neural.lua
+++ b/lualib/plugins/neural.lua
@@ -54,6 +54,9 @@ local default_options = {
   learning_spawned = false,
   ann_expire = 60 * 60 * 24 * 2, -- 2 days
   hidden_layer_mult = 1.5, -- number of neurons in the hidden layer
+  -- Check ROC curve and AUC in the ML literature
+  spam_score_threshold = nil, -- neural score threshold for spam (must be 0..1 or nil to disable)
+  ham_score_threshold = nil, -- neural score threshold for ham (must be 0..1 or nil to disable)
   symbol_spam = 'NEURAL_SPAM',
   symbol_ham = 'NEURAL_HAM',
   max_inputs = nil, -- when PCA is used
diff --git a/src/plugins/lua/neural.lua b/src/plugins/lua/neural.lua
index 894d42e30..ca11d9e66 100644
--- a/src/plugins/lua/neural.lua
+++ b/src/plugins/lua/neural.lua
@@ -119,10 +119,24 @@ local function ann_scores_filter(task)
 
       if score > 0 then
         local result = score
-        task:insert_result(rule.symbol_spam, result, symscore)
+
+        if not rule.spam_score_threshold or result >= rule.spam_score_threshold then
+          task:insert_result(rule.symbol_spam, result, symscore)
+        else
+          lua_util.debugm(N, task, '%s:%s:%s ann score: %s < %s (spam_score_threshold)',
+              rule.prefix, set.name, set.ann.version, symscore,
+              rule.spam_score_threshold)
+        end
       else
         local result = -(score)
-        task:insert_result(rule.symbol_ham, result, symscore)
+
+        if not rule.ham_score_threshold or result >= rule.ham_score_threshold then
+          task:insert_result(rule.symbol_ham, result, symscore)
+        else
+          lua_util.debugm(N, task, '%s:%s:%s ann score: %s < %s (ham_score_threshold)',
+              rule.prefix, set.name, set.ann.version, result,
+              rule.ham_score_threshold)
+        end
       end
     end
   end