- * Usually GiNaC tries heuristic GCD algorithm before PRS.
- * Some people don't like this, so here's a flag to disable it.
+ * Usually GiNaC tries heuristic GCD first, because typically
+ * it's much faster than anything else. Even if heuristic
+ * algorithm fails, the overhead is negligible w.r.t. cost
+ * of computing the GCD by some other method. However, some
+ * people dislike it, so here's a flag which tells GiNaC
+ * to NOT use the heuristic algorithm.