Correct updating of forward probabilities at first site

Author: szhan

python/tests/beagle_numba.py

@@ -357,11 +357,9 @@ def compute_forward_matrix(ref_h, query_h, trans_probs, mismatch_probs):
             if query_a == ref_a:
                 em_prob = 1.0 - mismatch_probs[i]
             fwd_mat[i, j] = em_prob
-            if i == 0:
-                fwd_mat[i, j] *= 1.0 / h  # Prior probabilities.
-            else:
-                fwd_mat[i, j] *= scale * fwd_mat[i - 1, j] + shift
+            fwd_mat[i, j] *= scale * fwd_mat[i - 1, j] + shift
         site_sum = np.sum(fwd_mat[i, :])
+        # Prior probabilities are multiplied when i = 0.
         last_sum = site_sum / h if i == 0 else site_sum
     return fwd_mat