1 files changed, 149 insertions, 67 deletions

diff --git a/decoder/ff_fsa.h b/decoder/ff_fsa.h
index a14f9913..3096f049 100755
--- a/decoder/ff_fsa.h
+++ b/decoder/ff_fsa.h
@@ -1,6 +1,8 @@
 #ifndef FF_FSA_H
 #define FF_FSA_H
 
+//SEE ALSO: ff_fsa_dynamic.h, ff_from_fsa.h
+
 //TODO: actually compile this; probably full of syntax errors.
 
 #include <stdint.h> //C99
@@ -10,6 +12,7 @@
 #include "value_array.h" // used to hold state
 #include "tdict.h"
 #include "hg.h"
+#include "sentences.h"
 
 typedef ValueArray<uint8_t> Bytes;
 
@@ -18,92 +21,171 @@ typedef ValueArray<uint8_t> Bytes;
 
   state is some fixed width byte array.  could actually be a void *, WordID sequence, whatever.
 
- */
+*/
 
-// it's not necessary to inherit from this.
+// it's not necessary to inherit from this, but you probably should to save yourself some boilerplate.  defaults to no-state
 struct FsaFeatureFunctionBase {
-  std::string name,usage_short,usage_verbose;
-  int fid; // you can have more than 1 feature of course.
-  void InitFid() { // call this, though, if you have a single feature
-    fid=FD::Convert(name);
+protected:
+  Bytes start,h_start; // start state and estimated-features (heuristic) start state.  set these.  default empty.
+  Sentence end_phrase_; // words appended for final traversal (final state cost is assessed using Scan) e.g. "</s>" for lm.
+  int state_bytes_; // don't forget to set this. default 0 (it may depend on params of course)
+  void set_state_bytes(int sb=0) {
+    state_bytes_=sb;
   }
-  std::string usage(bool param,bool verbose) {
-    return FeatureFunction::usage_helper(name,usage_short,usage_verbose,param,verbose);
+
+  int fid_; // you can have more than 1 feature of course.
+  void init_fid(std::string const& name) { // call this, though, if you have a single feature
+    fid_=FD::Convert(name);
   }
+public:
 
-  FsaFeatureFunctionBase(std::string const& name,std::string const& usage_verbose="[no documentation yet]",std::string const& usage_short="[no parameters]") : name(name),usage_short(usage_short),usage_verbose(usage_verbose) {  }
+  // return m: all strings x with the same final m+1 letters must end in this state
+  /* markov chain of order m: P(xn|xn-1...x1)=P(xn|xn-1...xn-m) */
+  int markov_order() const { return 0; } // override if you use state.  order 0 implies state_bytes()==0 as well, as far as scoring/splitting is concerned (you can still track state, though)
+  //TODO: if we wanted, we could mark certain states as maximal-context, but this would lose our fixed amount of left context in ff_from_fsa, and lose also our vector operations (have to scan left words 1 at a time, checking always to see where you change from h to inside - BUT, could detect equivalent LM states, which would be nice).
 
-  int state_bytes; // don't forget to set this (it may depend on params of course)
-};
+  Features features() const { // override this if >1 fid
+    return FeatureFunction::single_feature(fid_);
+  }
 
-// example: feature val = -1 * # of target words
-struct TargetPenaltyFsa : public FsaFeatureFunctionBase {
-  TargetPenaltyFsa(std::string const& param) : FsaFeatureFunctionBase("TargetPenalty","","-1 per target word") { InitFid(); }
-  const float val_per_target_word=-1;
-  // state for backoff
+  // override this (static)
+  static std::string usage(bool param,bool verbose) {
+    return FeatureFunction::usage_helper("unnamed_fsa_feature","","",param,verbose);
+  }
+  int state_bytes() const { return state_bytes_; } // or override this
+  void const* start_state() const {
+    return start.begin();
+  }
+  void const * heuristic_start_state() const {
+    return h_start.begin();
+  }
+  Sentence const& end_phrase() const { return end_phrase_; }
+  // move from state to next_state after seeing word x, while emitting features->add_value(fid,val) possibly with duplicates.  state and next_state will never be the same memory.
+  //TODO: decide if we want to require you to support dest same as src, since that's how we use it most often in ff_from_fsa bottom-up wrapper (in l->r scoring, however, distinct copies will be the rule), and it probably wouldn't be too hard for most people to support.  however, it's good to hide the complexity here, once (see overly clever FsaScan loop that swaps src/dest addresses repeatedly to scan a sequence by effectively swapping)
 
-  // scan
-  void Scan(SentenceMetadata const& smeta,WordID x,void const* prev_state,FeatureVector *features) {
-    features->set_value(fid,val_per_target_word);
+  // NOTE: if you want to e.g. track statistics, cache, whatever, cast const away or use mutable members
+  void Scan(SentenceMetadata const& smeta,WordID x,void const* state,void *next_state,FeatureVector *features) const {
   }
 
-  // heuristic estimate of phrase
-  void Heuristic(WordID const* begin, WordID const* end,FeatureVector *h_features)
+  // don't set state-bytes etc. in ctor because it may depend on parsing param string
+  FsaFeatureFunctionBase() : start(0),h_start(0),state_bytes_(0) {  }
 
-  // return m: all strings x with the same final m+1 letters must end in this state
-  /* markov chain of order m: P(xn|xn-1...x1)=P(xn|xn-1...xn-m) */
-  int MarkovOrder() const {
-    return 0;
+};
+
+
+
+// init state is in cs; overwrite cs, ns repeatedly (alternatively).  return resulting state
+template <class FsaFF>
+void *FsaScan(FsaFF const& ff,SentenceMetadata const& smeta,WordID const* i, WordID const* end,FeatureVector *h_features, void *cs,void *ns) {
+  // extra code - IT'S FOR EFFICIENCY, MAN!  IT'S OK!  definitely no bugs here.
+  void *os,*es;
+  WordID const* e=end-1; // boundcheck 1 earlier because in loop below we use i+1 before rechecking
+  if ((end-i)&1) { // odd # of words
+    os=cs;
+    es=ns;
+    i-=1;
+    goto odd;
+  } else {
+    es=cs;
+    os=ns;
+  }
+  for (;i<e;i+=2) {
+    ff.Scan(smeta,*i,es,os,h_features); // e->o
+  odd:
+    ff.Scan(smeta,*(i+1),os,es,h_features); // o->e
+  }
+  return es;
+}
+
+// do not use if state size is 0, please.
+const bool optimize_FsaScanner_zerostate=false;
+
+template <class FF>
+struct FsaScanner {
+//  enum {ALIGN=8};
+  static const int ALIGN=8;
+  FF const& ff;
+  SentenceMetadata const& smeta;
+  int ssz;
+  Bytes states; // first is at begin, second is at (char*)begin+stride
+  void *st0; // states
+  void *st1; // states+stride
+  void *cs;
+  inline void *nexts() const {
+    return (cs==st0)?st1:st0;
+  }
+  FsaScanner(FF const& ff,SentenceMetadata const& smeta) : ff(ff),smeta(smeta)
+  {
+    ssz=ff.state_bytes();
+    int stride=((ssz+ALIGN-1)/ALIGN)*ALIGN; // round up to multiple of ALIGN
+    states.resize(stride+ssz);
+    st0=states.begin();
+    st1=(char*)st0+stride;
+//    for (int i=0;i<2;++i) st[i]=cs+(i*stride);
+  }
+  void reset(void const* state) {
+    cs=st0;
+    std::memcpy(st0,state,ssz);
+  }
+  void scan(WordID w,FeatureVector *feat) {
+    if (optimize_FsaScanner_zerostate && !ssz) {
+      ff.Scan(smeta,w,0,0,feat);
+      return;
+    }
+    void *ns=nexts();
+    ff.Scan(smeta,w,cs,ns,feat);
+    cs=ns;
   }
 
+  void scan(WordID const* i,WordID const* end,FeatureVector *feat) {
+#if 1
+    // faster.
+    if (optimize_FsaScanner_zerostate && !ssz)
+      for (;i<end;++i)
+        ff.Scan(smeta,*i,0,0,feat);
+    else
+      cs=FsaScan(ff,smeta,i,end,feat,cs,nexts());
+#else
+    for (;i<end;++i)
+      scan(*i,feat);
+#endif
+  }
 };
 
-//TODO: combine 2 FsaFeatures typelist style (can recurse for more)
 
-// the type-erased interface
-struct FsaFeatureFunction {
-  virtual int MarkovOrder() const = 0;
-  virtual ~FsaFeatureFunction();
+template <class FF>
+void AccumFeatures(FF const& ff,SentenceMetadata const& smeta,WordID const* i, WordID const* end,FeatureVector *h_features,void const* start_state) {
+  int ssz=ff.state_bytes();
+  if (ssz) {
+    Bytes state(ssz),state2(ssz);
+    void *cs=state.begin(),*ns=state2.begin();
+    memcpy(cs,start_state,ff.state_bytes());
+    FsaScan(ff,smeta,i,end,h_features,cs,ns);
+  } else
+    for (;i<end;++i)
+      ff.Scan(smeta,*i,0,0,h_features);
+}
 
-};
 
-// conforming to above interface, type erases FsaImpl
-// you might be wondering: why do this?  answer: it's cool, and it means that the bottom-up ff over ff_fsa wrapper doesn't go through multiple layers of dynamic dispatch
-template <class Impl>
-struct FsaFeatureFunctionDynamic : public FsaFeatureFunction {
-  Impl& d() { return static_cast<Impl&>(*this); }
-  Impl const& d() { return static_cast<Impl const&>(*this); }
-  int MarkovOrder() const { return d().MarkovOrder(); }
-};
+//TODO: combine 2 FsaFeatures typelist style (can recurse for more)
 
-//TODO: combine 2 (or N) FsaFeatureFunction (type erased)
-
-/* regular bottom up scorer from Fsa feature
-   uses guarantee about markov order=N to score ASAP
-   encoding of state: if less than N-1 (ctxlen) words
-
-   either:
-   struct FF : public FsaImpl,FeatureFunctionFromFsa<FF> (more efficient)
-
-   or:
-   struct FF : public FsaFeatureFunctionDynamic,FeatureFunctionFromFsa<FF> (code sharing, but double dynamic dispatch)
- */
-
-template <class Impl>
-struct FeatureFunctionFromFsa : public FeatureFunction {
-  Impl& d() { return static_cast<Impl&>(*this); }
-  Impl const& d() { return static_cast<Impl const&>(*this); }
-  int M; // markov order (ctx len)
-  FeatureFunctionFromFsa() {  }
-  Init() {
-    name=d().name;
-    M=d().MarkovOrder
-    SetStateSize(sizeof(WordID)*2*M);
-  } // can't do this in constructor because we come before d() in order
-
-  virtual Features Features() const { return d().Features(); }
-  bool rule_feature() const {
-    return StateSize()==0; // Fsa features don't get info about span
+// example: feature val = -1 * # of target words
+struct WordPenaltyFsa : public FsaFeatureFunctionBase {
+  WordPenaltyFsa(std::string const& param) {
+    init_fid(usage(false,false));
+    return;
+    //below are all defaults:
+    set_state_bytes(0);
+    start.clear();
+    h_start.clear();
+  }
+  static const float val_per_target_word=-1;
+  // move from state to next_state after seeing word x, while emitting features->add_value(fid,val) possibly with duplicates.  state and next_state may be same memory.
+  void Scan(SentenceMetadata const& smeta,WordID x,void const* state,void *next_state,FeatureVector *features) const {
+    features->add_value(fid_,val_per_target_word);
+  }
+  static std::string usage(bool param,bool verbose) {
+    return FeatureFunction::usage_helper("WordPenaltyFsa","","-1 per target word",param,verbose);
   }
 
 };