add target andsteady state iters

sho/iters.py

@@ -1,16 +1,50 @@
 import sys
+from collections import deque
 
 ########################################################################
 # Stopping criterions
 ########################################################################
 
 def max(i, val, sol, nb_it):
+    """Stop after reaching nb_it iterations."""
     if i < nb_it:
         return True
     else:
         return False
 
 
+def target(i, val, sol, target):
+    """Stop after reaching target value."""
+    if val < target:
+        return True
+    else:
+        return False
+
+
+class steady:
+    """Stop if improvement is lesser than epsilon, in the last delta iterations."""
+
+    def __init__(self, delta, epsilon = 0):
+        self.epsilon = epsilon
+        self.delta = delta
+        self.delta_vals = deque()
+
+    def __call__(self, i, val, sol):
+        if i < self.delta: # Always wait the first delta iterations.
+            self.delta_vals.append(val)
+            return True
+
+        else:
+            #FILO stack.
+            self.delta_vals.popleft()
+            self.delta_vals.append(val)
+
+            if val - self.delta_vals[0] <= self.epsilon:
+                return False # Stop here.
+            else:
+                return True
+
+
 # Stopping criterions that are actually just checkpoints.
 
 def several(i, val, sol, agains):