Fix logical flaws in AuthorDiversityScorer and WeightedScorer

home-mixer/demonstrate_fixes.rs

@@ -0,0 +1,69 @@
+fn main() {
+    println!("=== Demonstration of Fixes for Ranking Algorithms ===\n");
+
+    demonstrate_diversity_fix();
+    println!("\n-----------------------------------------------------\n");
+    demonstrate_weighted_scorer_fix();
+}
+
+fn demonstrate_diversity_fix() {
+    println!("1. Author Diversity Scorer Fix");
+    println!("Scenario: A candidate has a negative score (e.g., -100.0) due to negative signals.");
+    println!("          It is the 2nd post from the same author, so a decay factor (0.5) applies.");
+
+    let score = -100.0;
+    let multiplier = 0.5;
+
+    // Old Logic
+    let old_score = score * multiplier;
+
+    // New Logic
+    let new_score = if score > 0.0 {
+        score * multiplier
+    } else {
+        score
+    };
+
+    println!("\nInput Score: {}", score);
+    println!("Diversity Multiplier: {}", multiplier);
+    println!("Before Fix (Old Logic): {} (BOOSTED! -50 is better than -100)", old_score);
+    println!("After Fix (New Logic):  {} (CORRECT - score remains low)", new_score);
+}
+
+fn demonstrate_weighted_scorer_fix() {
+    println!("2. Weighted Scorer Fix");
+    println!("Scenario: Comparing scores just above and below zero to check for continuity.");
+    println!("          Constants: WEIGHTS_SUM=200, NEGATIVE_SCORES_OFFSET=50, NEGATIVE_WEIGHTS_SUM=-100");
+
+    let score_neg = -0.001;
+    let score_pos = 0.001;
+
+    // Constants mocking the params module
+    let weights_sum = 200.0;
+    let negative_weights_sum = -100.0;
+    let negative_scores_offset = 50.0;
+
+    // Old Logic Function
+    let old_logic = |s: f64| -> f64 {
+        if s < 0.0 {
+            (s + negative_weights_sum) / weights_sum * negative_scores_offset
+        } else {
+            s + negative_scores_offset
+        }
+    };
+
+    // New Logic Function
+    let new_logic = |s: f64| -> f64 {
+        s + negative_scores_offset
+    };
+
+    println!("\n-- Before Fix (Discontinuity) --");
+    println!("Score -0.001 -> {:.4}", old_logic(score_neg));
+    println!("Score +0.001 -> {:.4}", old_logic(score_pos));
+    println!("Gap: {:.4} (Huge jump at zero!)", (old_logic(score_pos) - old_logic(score_neg)).abs());
+
+    println!("\n-- After Fix (Continuous) --");
+    println!("Score -0.001 -> {:.4}", new_logic(score_neg));
+    println!("Score +0.001 -> {:.4}", new_logic(score_pos));
+    println!("Gap: {:.4} (Smooth transition)", (new_logic(score_pos) - new_logic(score_neg)).abs());
+}

home-mixer/scorers/author_diversity_scorer.rs

@@ -55,7 +55,13 @@ impl Scorer<ScoredPostsQuery, PostCandidate> for AuthorDiversityScorer {
             *entry += 1;
 
             let multiplier = self.multiplier(position);
-            let adjusted_score = candidate.weighted_score.map(|score| score * multiplier);
+            let adjusted_score = candidate.weighted_score.map(|score| {
+                if score > 0.0 {
+                    score * multiplier
+                } else {
+                    score
+                }
+            });
 
             let updated = PostCandidate {
                 score: adjusted_score,

home-mixer/scorers/weighted_scorer.rs

@@ -83,8 +83,6 @@ impl WeightedScorer {
     fn offset_score(combined_score: f64) -> f64 {
         if p::WEIGHTS_SUM == 0.0 {
             combined_score.max(0.0)
-        } else if combined_score < 0.0 {
-            (combined_score + p::NEGATIVE_WEIGHTS_SUM) / p::WEIGHTS_SUM * p::NEGATIVE_SCORES_OFFSET
         } else {
             combined_score + p::NEGATIVE_SCORES_OFFSET
         }