From bbdb3cd485b829b6236258cef8e0b3cb1a3c4ecf Mon Sep 17 00:00:00 2001
From: Chris Dyer <cdyer@cs.cmu.edu>
Date: Tue, 8 Mar 2011 14:40:38 -0500
Subject: support multiple LMs with different feature names

---
 decoder/ff_klm.cc | 70 ++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 57 insertions(+), 13 deletions(-)

diff --git a/decoder/ff_klm.cc b/decoder/ff_klm.cc
index 203bced5..854653c3 100644
--- a/decoder/ff_klm.cc
+++ b/decoder/ff_klm.cc
@@ -2,6 +2,7 @@
 
 #include <cstring>
 
+#include "stringlib.h"
 #include "hg.h"
 #include "tdict.h"
 #include "lm/enumerate_vocab.hh"
@@ -12,6 +13,49 @@ static const unsigned char HAS_FULL_CONTEXT = 1;
 static const unsigned char HAS_EOS_ON_RIGHT = 2;
 static const unsigned char MASK             = 7;
 
+// -x : rules include <s> and </s>
+// -n NAME : feature id is NAME
+bool ParseLMArgs(string const& in, string* filename, bool* explicit_markers, string* featname) {
+  vector<string> const& argv=SplitOnWhitespace(in);
+  *explicit_markers = true;
+  *featname="LanguageModel";
+#define LMSPEC_NEXTARG if (i==argv.end()) {            \
+    cerr << "Missing argument for "<<*last<<". "; goto usage; \
+    } else { ++i; }
+
+  for (vector<string>::const_iterator last,i=argv.begin(),e=argv.end();i!=e;++i) {
+    string const& s=*i;
+    if (s[0]=='-') {
+      if (s.size()>2) goto fail;
+      switch (s[1]) {
+      case 'x':
+        *explicit_markers = true;
+        break;
+      case 'n':
+        LMSPEC_NEXTARG; *featname=*i;
+        break;
+#undef LMSPEC_NEXTARG
+      default:
+      fail:
+        cerr<<"Unknown KLanguageModel option "<<s<<" ; ";
+        goto usage;
+      }
+    } else {
+      if (filename->empty())
+        *filename=s;
+      else {
+        cerr<<"More than one filename provided. ";
+        goto usage;
+      }
+    }
+  }
+  if (!filename->empty())
+    return true;
+usage:
+  cerr << "KLanguageModel is incorrect!\n";
+  return false;
+}
+
 template <class Model>
 string KLanguageModel<Model>::usage(bool /*param*/,bool /*verbose*/) {
   return "KLanguageModel";
@@ -212,19 +256,14 @@ class KLanguageModelImpl {
   }
 
  public:
-  KLanguageModelImpl(const std::string& param) {
-    add_sos_eos_ = true;
-    string fname = param;
-    if (param.find("-x ") == 0) {
-       add_sos_eos_ = false;
-       fname = param.substr(3);
-    }
+  KLanguageModelImpl(const string& filename, bool explicit_markers) :
+      add_sos_eos_(!explicit_markers) {
     lm::ngram::Config conf;
     VMapper vm(&map_);
     conf.enumerate_vocab = &vm; 
-    ngram_ = new Model(fname.c_str(), conf);
+    ngram_ = new Model(filename.c_str(), conf);
     order_ = ngram_->Order();
-    cerr << "Loaded " << order_ << "-gram KLM from " << fname << " (MapSize=" << map_.size() << ")\n";
+    cerr << "Loaded " << order_ << "-gram KLM from " << filename << " (MapSize=" << map_.size() << ")\n";
     state_size_ = ngram_->StateSize() + 2 + (order_ - 1) * sizeof(lm::WordIndex);
     unscored_size_offset_ = ngram_->StateSize();
     is_complete_offset_ = unscored_size_offset_ + 1;
@@ -252,7 +291,7 @@ class KLanguageModelImpl {
   lm::WordIndex kSOS_;  // <s> - requires special handling.
   lm::WordIndex kEOS_;  // </s>
   Model* ngram_;
-  bool add_sos_eos_; // flag indicating whether the hypergraph produces <s> and </s>
+  const bool add_sos_eos_; // flag indicating whether the hypergraph produces <s> and </s>
                      // if this is true, FinalTransitionFeatures will "add" <s> and </s>
                      // if false, FinalTransitionFeatures will score anything with the
                      // markers in the right place (i.e., the beginning and end of
@@ -271,9 +310,14 @@ class KLanguageModelImpl {
 
 template <class Model>
 KLanguageModel<Model>::KLanguageModel(const string& param) {
-  pimpl_ = new KLanguageModelImpl<Model>(param);
-  fid_ = FD::Convert("LanguageModel");  // todo support LM feature name
-  oov_fid_ = FD::Convert("OOV");        // should also be named
+  string filename, featname;
+  bool explicit_markers;
+  if (!ParseLMArgs(param, &filename, &explicit_markers, &featname)) {
+    abort();
+  }
+  pimpl_ = new KLanguageModelImpl<Model>(filename, explicit_markers);
+  fid_ = FD::Convert(featname);
+  oov_fid_ = FD::Convert(featname+"_OOV");
   SetStateSize(pimpl_->ReserveStateSize());
 }
 
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