Added test for 2 vs 2. It fails... need to figure out why.

src/lib.rs

@@ -174,19 +174,22 @@ where
         })
         .collect::<Vec<_>>();
 
-    let epsilon = draw_margin(DRAW_PROBABILITY, BETA, 2.0);
-
     let trunc_layer = team_diff_vars
         .iter()
         .enumerate()
         .map(|(i, variable)| {
             factor_id += 1;
 
+            let player_count = perf_vars
+                .iter()
+                .filter(|(_, team)| *team as usize == i || *team as usize == i + 1)
+                .count();
+
             TruncateFactor::new(
                 &mut variable_arena,
                 factor_id,
                 *variable,
-                epsilon,
+                draw_margin(DRAW_PROBABILITY, BETA, player_count as f64),
                 ranks[i] == ranks[i + 1],
             )
 
@@ -350,7 +353,7 @@ mod tests {
     }
 
     #[test]
-    fn test_rate_4vs4() {
+    fn test_rate_4_free_for_all() {
         let alice = Rating::new(MU, SIGMA);
         let bob = Rating::new(MU, SIGMA);
         let chris = Rating::new(MU, SIGMA);
@@ -387,4 +390,26 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_rate_2vs2() {
+        let alice = Rating::new(MU, SIGMA);
+        let bob = Rating::new(MU, SIGMA);
+        let chris = Rating::new(MU, SIGMA);
+        let darren = Rating::new(MU, SIGMA);
+
+        let expected_ratings = vec![
+            Rating::new(28.108322399069035, 7.77436345109384),
+            Rating::new(28.108322399069035, 7.77436345109384),
+            Rating::new(21.891677600930958, 7.77436345109384),
+            Rating::new(21.891677600930958, 7.77436345109384),
+        ];
+
+        let ratings = rate(&[(alice, 0), (bob, 0), (chris, 1), (darren, 1)], &[0, 1]);
+
+        for (rating, expected) in ratings.iter().zip(expected_ratings.iter()) {
+            assert_relative_eq!(rating, expected, epsilon = EPSILON);
+        }
+    }
+
+
 }