[pypy-svn] r32899 - pypy/dist/pypy/lib/constraint

[auc at codespeak.net]

Author: auc
Date: Thu Oct  5 10:04:59 2006
New Revision: 32899

Added:
   pypy/dist/pypy/lib/constraint/
   pypy/dist/pypy/lib/constraint/__init__.py   (contents, props changed)
   pypy/dist/pypy/lib/constraint/solver.py   (contents, props changed)
Log:
solver belongs to lib


Added: pypy/dist/pypy/lib/constraint/__init__.py
==============================================================================

Added: pypy/dist/pypy/lib/constraint/solver.py
==============================================================================
--- (empty file)
+++ pypy/dist/pypy/lib/constraint/solver.py	Thu Oct  5 10:04:59 2006
@@ -0,0 +1,87 @@
+
+class StrategyDistributionMismatch(Exception):
+    pass
+
+
+from collections import deque
+
+class Depth: pass
+class Breadth: pass
+
+#-- pythonic lazy solve_all (takes space)
+
+def lazily_iter_solve_all(space, direction=Depth):
+
+    sp_stack = deque([])
+    sp_stack.append(space)
+
+    if direction == Depth:
+        def collect(space):
+            sp_stack.append(space)
+    else:
+        def collect(space):
+            sp_stack.appendleft(space)
+
+    print "ready to find solution ..."
+    while sp_stack:
+        space = sp_stack.pop()
+        print ' '*len(sp_stack), "ask [depth = %s]" % len(sp_stack)
+        status = space.ask()
+        if status == 1:
+            print ' '*len(sp_stack), "solution !"
+            yield space.merge()
+        elif status > 1:
+            print ' '*len(sp_stack), "%s branches ..." % status
+            for i in xrange(status):
+                clone = space.clone()
+                clone.commit(status-i)
+                collect(clone)
+        elif status == 0:
+            print ' '*len(sp_stack), "dead-end"
+
+solve = lazily_iter_solve_all
+
+
+#-- dfs with recomputations
+
+
+def recompute(space, branches_list):
+    # branches_list contains the recomputation path,
+    # bottom-up
+    if branches_list == None:
+        return space.clone()
+    else:
+        head, tail = branches_list
+        C = recompute(space, tail)
+        C.ask()
+        C.commit(head)
+        return C
+
+def dfre(S, R, branches_list, distance, max_dist, solutions):
+    status = S.ask()
+    if status == 0:
+        return
+    elif status == 1:
+        solutions.append(S.merge())
+        return
+    else:
+        assert status == 2
+        if distance == max_dist:
+            C = S.clone()
+            S.commit(1)
+            dfre(S, C, (1,None), 1, max_dist, solutions)
+            C.commit(2)
+            dfre(C, C, None, max_dist, max_dist, solutions)
+        else:
+            S.commit(1)
+            dfre(S, R, (1, branches_list), distance+1, max_dist, solutions)
+            C = recompute(R, branches_list)
+            C.ask()
+            C.commit(2)
+            dfre(C, R, (2, branches_list), distance+1, max_dist, solutions)
+
+def solve_recomputing(space, recomputation_distance=5):
+    solutions = []
+    dfre(space, space, None, recomputation_distance, recomputation_distance, solutions)
+    return solutions
+