add PolyLearner: polynomial learning scheduler

onn.py

@@ -766,6 +766,18 @@ class NoisyRitual(Ritual):
 
 # Learners {{{1
 
+class PolyLearner(Learner):
+    per_batch = True
+
+    def __init__(self, optim, epochs=400, coeffs=(1,)):
+        self.coeffs = tuple(coeffs)
+        super().__init__(optim, epochs, np.polyval(self.coeffs, 0))
+
+    def rate_at(self, epoch):
+        progress = (epoch - 1) / (self.epochs)
+        ret = np.polyval(self.coeffs, progress)
+        return np.abs(ret)
+
 class DumbLearner(AnnealingLearner):
     # this is my own awful contraption. it's not really "SGD with restarts".
     def __init__(self, optim, epochs=100, rate=None, halve_every=10,