From f051e98fb35c4ce69e489ef6550840bd6cd617fd Mon Sep 17 00:00:00 2001
From: Patrick Simianer <simianer@cl.uni-heidelberg.de>
Date: Mon, 11 Feb 2013 17:10:29 +0100
Subject: fixed l1 regularization iteration silliness

---
 training/dtrain/dtrain.cc | 39 ++++++++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 17 deletions(-)

diff --git a/training/dtrain/dtrain.cc b/training/dtrain/dtrain.cc
index 18286668..b317c365 100644
--- a/training/dtrain/dtrain.cc
+++ b/training/dtrain/dtrain.cc
@@ -246,7 +246,7 @@ main(int argc, char** argv)
     cerr << setw(25) << "k " << k << endl;
     cerr << setw(25) << "N " << N << endl;
     cerr << setw(25) << "T " << T << endl;
-    cerr << setw(25) << "scorer '" << scorer_str << "'" << endl;
+    cerr << setw(26) << "scorer '" << scorer_str << "'" << endl;
     if (scorer_str == "approx_bleu")
       cerr << setw(25) << "approx. B discount " << approx_bleu_d << endl;
     cerr << setw(25) << "sample from " << "'" << sample_from << "'" << endl;
@@ -459,35 +459,40 @@ main(int argc, char** argv)
       }
 
       // l1 regularization
+      // please note that this penalizes _all_ weights
+      // (contrary to only the ones changed by the last update)
+      // after a _sentence_ (not after each example/pair)
       if (l1naive) {
-        for (unsigned d = 0; d < lambdas.size(); d++) {
-          weight_t v = lambdas.get(d);
-          lambdas.set_value(d, v - sign(v) * l1_reg);
+        FastSparseVector<weight_t>::iterator it = lambdas.begin();
+        for (; it != lambdas.end(); ++it) {
+          it->second -= sign(it->second) * l1_reg;
         }
       } else if (l1clip) {
-        for (unsigned d = 0; d < lambdas.size(); d++) {
-          if (lambdas.nonzero(d)) {
-            weight_t v = lambdas.get(d);
+        FastSparseVector<weight_t>::iterator it = lambdas.begin();
+        for (; it != lambdas.end(); ++it) {
+          if (it->second != 0) {
+            weight_t v = it->second;
             if (v > 0) {
-              lambdas.set_value(d, max(0., v - l1_reg));
+              it->second = max(0., v - l1_reg);
             } else {
-              lambdas.set_value(d, min(0., v + l1_reg));
+              it->second = min(0., v + l1_reg);
             }
           }
         }
       } else if (l1cumul) {
         weight_t acc_penalty = (ii+1) * l1_reg; // ii is the index of the current input
-        for (unsigned d = 0; d < lambdas.size(); d++) {
-          if (lambdas.nonzero(d)) {
-            weight_t v = lambdas.get(d);
-            weight_t penalty = 0;
+        FastSparseVector<weight_t>::iterator it = lambdas.begin();
+        for (; it != lambdas.end(); ++it) {
+          if (it->second != 0) {
+            weight_t v = it->second;
+            weight_t penalized = 0.;
             if (v > 0) {
-              penalty = max(0., v-(acc_penalty + cumulative_penalties.get(d)));
+              penalized = max(0., v-(acc_penalty + cumulative_penalties.get(it->first)));
             } else {
-              penalty = min(0., v+(acc_penalty - cumulative_penalties.get(d)));
+              penalized = min(0., v+(acc_penalty - cumulative_penalties.get(it->first)));
             }
-            lambdas.set_value(d, penalty);
-            cumulative_penalties.set_value(d, cumulative_penalties.get(d)+penalty);
+            it->second = penalized;
+            cumulative_penalties.set_value(it->first, cumulative_penalties.get(it->first)+penalized);
           }
         }
       }
-- 
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