From ab3534c45f463e541f3baf05006a50b64e3bbe31 Mon Sep 17 00:00:00 2001
From: "trevor.cohn" <trevor.cohn@ec762483-ff6d-05da-a07a-a48fb63a330f>
Date: Mon, 28 Jun 2010 19:34:58 +0000
Subject: First bits of code for PR training

git-svn-id: https://ws10smt.googlecode.com/svn/trunk@44 ec762483-ff6d-05da-a07a-a48fb63a330f
---
 gi/posterior-regularisation/train_pr_global.py | 272 +++++++++++++++++++++++++
 1 file changed, 272 insertions(+)
 create mode 100644 gi/posterior-regularisation/train_pr_global.py

(limited to 'gi/posterior-regularisation/train_pr_global.py')

diff --git a/gi/posterior-regularisation/train_pr_global.py b/gi/posterior-regularisation/train_pr_global.py
new file mode 100644
index 00000000..467069ef
--- /dev/null
+++ b/gi/posterior-regularisation/train_pr_global.py
@@ -0,0 +1,272 @@
+import sys
+import scipy.optimize
+from numpy import *
+from numpy.random import random
+
+#
+# Step 1: load the concordance counts
+# 
+
+edges_phrase_to_context = {}
+edges_context_to_phrase = {}
+types = {}
+num_edges = 0
+
+for line in sys.stdin:
+    phrase, rest = line.strip().split('\t')
+    parts = rest.split('|||')
+    for i in range(0, len(parts), 2):
+        context, count = parts[i:i+2]
+
+        ctx = tuple(filter(lambda x: x != '<PHRASE>', context.split()))
+        cnt = int(count.strip()[2:])
+        ccs = edges_phrase_to_context.setdefault(phrase, {})
+        ccs[ctx] = cnt
+        pcs = edges_context_to_phrase.setdefault(ctx, {})
+        pcs[phrase] = cnt
+
+        for token in ctx:
+            types.setdefault(token, len(types))
+        for token in phrase.split():
+            types.setdefault(token, len(types))
+
+        num_edges += 1
+
+print 'Read in', num_edges, 'edges and', len(types), 'word types'
+
+#
+# Step 2: initialise the model parameters
+#
+
+num_tags = 5
+num_types = len(types)
+delta = int(sys.argv[1])
+gamma = int(sys.argv[2])
+
+def normalise(a):
+    return a / sum(a)
+
+# Pr(tag)
+tagDist = normalise(random(num_tags)+1)
+# Pr(context at pos i = w | tag) indexed by i, tag, word
+contextWordDist = [[normalise(random(num_types)+1) for t in range(num_tags)] for i in range(4)]
+# PR langrange multipliers
+lamba = zeros(num_edges * num_tags)
+lamba_index = {}
+next = 0
+for phrase, ccs in edges_phrase_to_context.items():
+    for context in ccs.keys():
+        lamba_index[phrase,context] = next
+        next += num_tags
+
+#
+# Step 3: expectation maximisation
+#
+
+for iteration in range(20):
+    tagCounts = zeros(num_tags)
+    contextWordCounts = [[zeros(num_types) for t in range(num_tags)] for i in range(4)]
+
+    #print 'tagDist', tagDist
+    #print 'contextWordCounts[0][0]', contextWordCounts[0][0]
+
+    # Tune lambda
+    # dual: min log Z(lamba) s.t. lamba >= 0;
+    # sum_c lamba_pct <= delta; sum_p lamba_pct <= gamma
+    def dual(ls):
+        logz = 0
+        for phrase, ccs in edges_phrase_to_context.items():
+            for context, count in ccs.items():
+                conditionals = zeros(num_tags)
+                for t in range(num_tags):
+                    prob = tagDist[t]
+                    for i in range(4):
+                        prob *= contextWordDist[i][t][types[context[i]]]
+                    conditionals[t] = prob
+                cz = sum(conditionals)
+                conditionals /= cz
+
+                local_z = 0
+                for t in range(num_tags):
+                    local_z += conditionals[t] * exp(-ls[lamba_index[phrase,context] + t])
+                logz += log(local_z) * count
+
+        #print 'ls', ls
+        #print 'lambda', list(ls)
+        #print 'dual', logz
+        return logz
+
+    def primal(ls):
+        # FIXME: returns negative values for KL (impossible)
+        logz = dual(ls)
+        kl = -logz
+
+        expectations = zeros(lamba.shape)
+        for phrase, ccs in edges_phrase_to_context.items():
+            for context, count in ccs.items():
+                conditionals = zeros(num_tags)
+                for t in range(num_tags):
+                    prob = tagDist[t]
+                    for i in range(4):
+                        prob *= contextWordDist[i][t][types[context[i]]]
+                    conditionals[t] = prob
+                cz = sum(conditionals)
+                conditionals /= cz
+
+                scores = zeros(num_tags)
+                for t in range(num_tags):
+                    scores[t] = conditionals[t] * exp(-ls[lamba_index[phrase,context] + t])
+                local_z = sum(scores)
+
+                for t in range(num_tags):
+                    li = lamba_index[phrase,context] + t
+                    expectations[li] = scores[t] / local_z * count
+                    kl -= expectations[li] * ls[li]
+
+        pt_l1linf = 0
+        for phrase, ccs in edges_phrase_to_context.items():
+            for t in range(num_tags):
+                best = -1e500
+                for context, count in ccs.items():
+                    li = lamba_index[phrase,context] + t
+                    s = expectations[li]
+                    if s > best: best = s
+                pt_l1linf += best
+
+        ct_l1linf = 0
+        for context, pcs in edges_context_to_phrase.items():
+            for t in range(num_tags):
+                best = -1e500
+                for phrase, count in pcs.items():
+                    li = lamba_index[phrase,context] + t
+                    s = expectations[li]
+                    if s > best: best = s
+                ct_l1linf += best
+
+        return kl, pt_l1linf, ct_l1linf, kl + delta * pt_l1linf + gamma * ct_l1linf
+
+    def dual_deriv(ls):
+        # d/dl log(z) = E_q[phi]
+        deriv = zeros(num_edges * num_tags)
+        for phrase, ccs in edges_phrase_to_context.items():
+            for context, count in ccs.items():
+                conditionals = zeros(num_tags)
+                for t in range(num_tags):
+                    prob = tagDist[t]
+                    for i in range(4):
+                        prob *= contextWordDist[i][t][types[context[i]]]
+                    conditionals[t] = prob
+                cz = sum(conditionals)
+                conditionals /= cz
+
+                scores = zeros(num_tags)
+                for t in range(num_tags):
+                    scores[t] = conditionals[t] * exp(-ls[lamba_index[phrase,context] + t])
+                local_z = sum(scores)
+
+                for t in range(num_tags):
+                    deriv[lamba_index[phrase,context] + t] -= count * scores[t] / local_z
+
+        #print 'ddual', deriv
+        return deriv
+
+    def constraints(ls):
+        cons = []
+        if delta > 0:
+            for phrase, ccs in edges_phrase_to_context.items():
+                for t in range(num_tags):
+                    total = delta
+                    for cprime in ccs.keys():
+                        total -= ls[lamba_index[phrase, cprime] + t]
+                    cons.append(total)
+
+        if gamma > 0:
+            for context, pcs in edges_context_to_phrase.items():
+                for t in range(num_tags):
+                    total = gamma
+                    for pprime in pcs.keys():
+                        total -= ls[lamba_index[pprime, context] + t]
+                    cons.append(total)
+        #print 'cons', cons
+        return cons
+
+    def constraints_deriv(ls):
+        cons = []
+        if delta > 0:
+            for phrase, ccs in edges_phrase_to_context.items():
+                for t in range(num_tags):
+                    d = zeros(num_edges * num_tags)
+                    for cprime in ccs.keys():
+                        d[lamba_index[phrase, cprime] + t] = -1
+                    cons.append(d)
+
+        if gamma > 0:
+            for context, pcs in edges_context_to_phrase.items():
+                for t in range(num_tags):
+                    d = zeros(num_edges * num_tags)
+                    for pprime in pcs.keys():
+                        d[lamba_index[pprime, context] + t] = -1
+                    cons.append(d)
+        #print 'dcons', cons
+        return cons
+
+    print 'Pre lambda optimisation dual', dual(lamba), 'primal', primal(lamba)
+    lamba = scipy.optimize.fmin_slsqp(dual, lamba,
+                            bounds=[(0, delta)] * (num_edges * num_tags),
+                            f_ieqcons=constraints,
+                            fprime=dual_deriv,
+                            fprime_ieqcons=constraints_deriv,
+                            iprint=0)
+    print 'Post lambda optimisation dual', dual(lamba), 'primal', primal(lamba)
+
+    # E-step
+    llh = z = 0
+    for phrase, ccs in edges_phrase_to_context.items():
+        for context, count in ccs.items():
+            conditionals = zeros(num_tags)
+            for t in range(num_tags):
+                prob = tagDist[t]
+                for i in range(4):
+                    prob *= contextWordDist[i][t][types[context[i]]]
+                conditionals[t] = prob
+            cz = sum(conditionals)
+            conditionals /= cz
+            llh += log(cz) * count
+
+            scores = zeros(num_tags)
+            li = lamba_index[phrase, context]
+            for t in range(num_tags):
+                scores[t] = conditionals[t] * exp(-lamba[li + t])
+            z += count * sum(scores)
+
+            tagCounts += count * scores
+            for i in range(4):
+                for t in range(num_tags):
+                    contextWordCounts[i][t][types[context[i]]] += count * scores[t]
+
+    print 'iteration', iteration, 'llh', llh, 'logz', log(z)
+
+    # M-step
+    tagDist = normalise(tagCounts)
+    for i in range(4):
+        for t in range(num_tags):
+            contextWordDist[i][t] = normalise(contextWordCounts[i][t])
+
+
+for phrase, ccs in edges_phrase_to_context.items():
+    for context, count in ccs.items():
+        conditionals = zeros(num_tags)
+        for t in range(num_tags):
+            prob = tagDist[t]
+            for i in range(4):
+                prob *= contextWordDist[i][t][types[context[i]]]
+            conditionals[t] = prob
+        cz = sum(conditionals)
+        conditionals /= cz
+
+        scores = zeros(num_tags)
+        li = lamba_index[phrase, context]
+        for t in range(num_tags):
+            scores[t] = conditionals[t] * exp(-lamba[li + t])
+
+        print '%s\t%s ||| C=%d ||| %d |||' % (phrase, context, count, argmax(scores)), scores / sum(scores)
-- 
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