Add vanilla MCTS/UCT algorithm for options

Generate options using UCT algorithm.
Useful for benchmarking.

Author: Jules Pondard

python/experimental/options_search/mcts.py

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+import tensor_comprehensions as tc
+import torch
+import my_utils
+import numpy as np
+#from tqdm import tqdm
+from visdom import Visdom
+
+viz = Visdom()
+
+class Node:
+    def __init__(self, father=None, new_act=0):
+        self.value = 0
+        self.values = []
+        self.nbVisits=0
+        self.nbChildrenSeen = 0
+        self.pos=0
+        #self.hasSeen = {} #todo
+        self.children=[]
+        self.parent = father
+        self.stateVector = [0] * my_utils.NB_HYPERPARAMS
+        if(father != None):
+            self.pos = father.pos+1
+            #self.hasSeen = {} #todo
+            self.stateVector = father.stateVector[:]
+            self.stateVector[self.pos-1] = new_act
+
+    def getRoot(self):
+        return self
+
+    def getParent(self):
+        return self.parent
+
+    def notRoot(self):
+        return (self.parent != None)
+
+class MCTS:
+    def __init__(self):
+        self.C = 1 #to tune
+
+        (tc_code, tc_name, inp, _) = my_utils.get_convolution_example(size_type="input", inp_sz_list=[8,2,28,28,8,1,1])
+
+        my_utils.computeCat(inp)
+        my_utils.set_tc(tc_code, tc_name)
+
+        self.nbActions = my_utils.cat_sz
+        self.tree = Node()
+
+        self.best_rewards = []
+        self.rws = []
+
+        self.curIter=0
+        self.curr_best=0
+        self.running_reward=0
+        self.win0 = viz.line(X=np.arange(5), Y=np.random.rand(5))
+
+    def main_search(self, starting_pos): #, init_inp):
+        node = starting_pos
+        #node.nbVisits+=1
+        ttNbIters = 10 #2*self.nbActions[node.pos]
+        for _ in range(max(ttNbIters, self.nbActions[node.pos])):
+            leaf = self.getLeaf(node)
+            val = self.evaluate(leaf)
+            self.backup(leaf, val)
+            #print(node.value / node.nbVisits)
+        _, action = self.getBestChild2(node)
+        return action
+
+    def take_action(self, node, act):
+        if(node.nbChildrenSeen > act):
+            return node.children[act]
+        new_child = Node(father=node, new_act=act)
+        node.children.append(new_child)
+        #node.hasSeen[act]=1
+        node.nbChildrenSeen += 1
+        return node.children[-1]
+
+    def getLeaf(self, node):
+        first=True
+        while(node.pos < my_utils.NB_HYPERPARAMS and (first or node.nbVisits != 0)):
+            first=False
+            pos = node.pos
+            if(node.nbChildrenSeen == self.nbActions[pos]):
+                node, _ = self.getBestChild(node)
+            else:
+                act=node.nbChildrenSeen
+                self.take_action(node, act)
+                return node.children[-1]
+        return node
+
+    def getBestChild2(self, node):
+        bestIndic = 0.
+        bestAction = 0
+        first=True
+        pos = node.pos
+        for act in range(self.nbActions[pos]):
+            child = node.children[act]
+            #indic = np.percentile(child.values, 20)
+            indic = child.value / child.nbVisits
+            if(first or indic > bestIndic):
+                bestIndic = indic
+                bestAction = act
+                first=False
+        return node.children[bestAction], bestAction
+
+    def getBestChild(self, node):
+        bestIndic = 0.
+        bestAction = 0
+        first=True
+        pos = node.pos
+        for act in range(self.nbActions[pos]):
+            child = node.children[act]
+            #indic = np.percentile(child.values, 20) + self.C * np.sqrt(2*np.log(node.nbVisits) / child.nbVisits)
+            indic = child.value / child.nbVisits + self.C * np.sqrt(2*np.log(node.nbVisits) / child.nbVisits)
+            if(first or indic > bestIndic):
+                bestIndic = indic
+                bestAction = act
+                first=False
+        return node.children[bestAction], bestAction
+
+    def saveReward(self, reward, opts):
+        INTER_DISP = 20
+        #print(-reward)
+        if(self.curIter == 0):
+            self.running_reward = reward
+            self.curr_best = reward
+        if(self.curIter == 0 or reward > self.curr_best):
+            print(-reward)
+            print(opts)
+        self.curIter += 1
+        self.running_reward = self.running_reward * 0.99 + reward * 0.01
+        self.curr_best = max(self.curr_best, reward)
+        #self.rewards.append(-reward)
+        self.best_rewards.append(-self.curr_best)
+        self.rws.append(-self.running_reward)
+        if self.curIter % INTER_DISP == 0:
+            viz.line(X=np.column_stack((np.arange(self.curIter), np.arange(self.curIter))), \
+            Y=np.column_stack((np.array(self.rws), np.array(self.best_rewards))), \
+            win=self.win0, opts=dict(legend=["Geometric run", "Best time"]))
+
+    def randomSampleScoreFrom(self, node):
+        pos = node.pos
+        optsVector = node.stateVector
+        for i in range(my_utils.NB_HYPERPARAMS - (pos)):
+            a = np.random.randint(self.nbActions[i+pos])
+            optsVector[i+(pos)] = a
+        #print(optsVector)
+        reward = -np.log(my_utils.evalTime(optsVector))
+        self.saveReward(reward, optsVector)
+        return reward
+
+    def evaluate(self, leaf):
+        score = 0
+        nb_iters=5
+        for _ in range(nb_iters):
+            score += self.randomSampleScoreFrom(leaf)
+        return score / nb_iters
+
+    def backup(self, leaf, val):
+        #if(val > 10.): #infty
+        #    return
+        node = leaf
+        while(node.notRoot()):
+            node.nbVisits += 1
+            #node.values.append(val)
+            node.value += val
+            node = node.getParent()
+        node.nbVisits += 1
+        node.value += val
+        node.values.append(val)
+
+mcts = MCTS()
+
+opts = []
+curr_node = mcts.tree
+for i in range(my_utils.NB_HYPERPARAMS):
+    opts.append(mcts.main_search(curr_node))
+    curr_node = mcts.take_action(curr_node, opts[-1])
+    print(opts)
+opts = np.array(opts).astype(int)
+print(my_utils.evalTime(opts.tolist()))
+my_utils.print_opt(opts)