Add method to find the best scoring position from a `StripedScores`

lightmotif/src/abc.rs

@@ -13,6 +13,11 @@ pub trait Symbol: Default + Sized + Copy + TryFrom<char> {
 pub trait Alphabet: Debug + Copy + Default + 'static {
     type Symbol: Symbol;
     const K: usize;
+
+    /// Get the default symbol for this alphabet.
+    fn default_symbol() -> Self::Symbol {
+        Default::default()
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Debug)]

lightmotif/src/pli.rs

@@ -257,6 +257,7 @@ impl<V: Vector, const C: usize> StripedScores<V, C> {
 }
 
 impl<const C: usize> StripedScores<f32, C> {
+    /// Convert the striped scores to a vector of scores.
     pub fn to_vec(&self) -> Vec<f32> {
         let mut vec = Vec::with_capacity(self.length);
         for i in 0..self.length {
@@ -266,18 +267,37 @@ impl<const C: usize> StripedScores<f32, C> {
         }
         vec
     }
+
+    /// Get the index of the highest scoring position.
+    ///
+    /// ## Panic
+    /// Panics if the data buffer is empty.
+    pub fn argmax(&self) -> usize {
+        let mut best_pos = 0;
+        let mut best_score = self.data[0][0];
+        for i in 0..self.length {
+            let col = i / self.data.rows();
+            let row = i % self.data.rows();
+            if self.data[row][col] > best_score {
+                best_pos = i;
+                best_score = self.data[row][col];
+            }
+        }
+        best_pos
+    }
 }
 
 #[cfg(target_feature = "avx2")]
 impl<const C: usize> StripedScores<__m256, C> {
+    /// Convert the striped scores to a vector of scores.
     pub fn to_vec(&self) -> Vec<f32> {
         // NOTE(@althonos): Because in AVX2 the __m256 vector is actually
         //                  two independent __m128, the shuffling creates
         //                  intrication in the results.
         #[rustfmt::skip]
         const COLS: &[usize] = &[
-             0,  1,  2,  3,  8,  9, 10, 11, 16, 17, 18, 19, 24, 25, 26, 27,
-             4,  5,  6,  7, 12, 13, 14, 15, 20, 21, 22, 23, 28, 29, 30, 31,
+            0,  1,  2,  3,  8,  9, 10, 11, 16, 17, 18, 19, 24, 25, 26, 27,
+            4,  5,  6,  7, 12, 13, 14, 15, 20, 21, 22, 23, 28, 29, 30, 31,
         ];
 
         let mut col = 0;
@@ -293,4 +313,27 @@ impl<const C: usize> StripedScores<__m256, C> {
         }
         vec
     }
+
+    /// Get the index of the highest scoring position.
+    ///
+    /// ## Panic
+    /// Panics if the data buffer is empty.
+    pub fn argmax(&self) -> usize {
+        let mut best_pos = 0;
+        let mut best_score = self.data[0][0];
+        let mut col = 0;
+        let mut row = 0;
+        for i in 0..self.length {
+            if self.data[row][col] > best_score {
+                best_pos = i;
+                best_score = self.data[row][col];
+            }
+            row += 1;
+            if row == self.data.rows() {
+                row = 0;
+                col += 1;
+            }
+        }
+        best_pos
+    }
 }

lightmotif/src/pwm.rs

@@ -162,11 +162,10 @@ pub struct Background<A: Alphabet, const K: usize> {
 
 impl<A: Alphabet, const K: usize> Background<A, K> {
     pub fn uniform() -> Self {
-
         let mut frequencies = [0.0; K];
         for i in 0..K {
             if i != A::default_symbol().as_index() {
-                frequencies[i] = 1.0 / ((K-1) as f32);
+                frequencies[i] = 1.0 / ((K - 1) as f32);
             }
         }