From ee41e4fea7609119655a6ad73ead2df4b754c552 Mon Sep 17 00:00:00 2001
From: Matthew Honnibal <honnibal+gh@gmail.com>
Date: Tue, 3 Oct 2017 12:43:48 +0200
Subject: [PATCH] Support history features in stateclass

---
 spacy/syntax/_state.pxd     | 30 ++++++++++++++++++++++++++++--
 spacy/syntax/stateclass.pyx |  8 ++++++++
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/spacy/syntax/_state.pxd b/spacy/syntax/_state.pxd
index 4fb16881a..f4fa49286 100644
--- a/spacy/syntax/_state.pxd
+++ b/spacy/syntax/_state.pxd
@@ -1,4 +1,4 @@
-from libc.string cimport memcpy, memset
+from libc.string cimport memcpy, memset, memmove
 from libc.stdlib cimport malloc, calloc, free
 from libc.stdint cimport uint32_t, uint64_t
 
@@ -15,6 +15,23 @@ from ..typedefs cimport attr_t
 cdef inline bint is_space_token(const TokenC* token) nogil:
     return Lexeme.c_check_flag(token.lex, IS_SPACE)
 
+cdef struct RingBufferC:
+    int[8] data
+    int i
+    int default
+
+cdef inline int ring_push(RingBufferC* ring, int value) nogil:
+    ring.data[ring.i] = value
+    ring.i += 1
+    if ring.i >= 8:
+        ring.i = 0
+
+cdef inline int ring_get(RingBufferC* ring, int i) nogil:
+    if i >= ring.i:
+        return ring.default
+    else:
+        return ring.data[ring.i-i]
+
 
 cdef cppclass StateC:
     int* _stack
@@ -23,6 +40,7 @@ cdef cppclass StateC:
     TokenC* _sent
     Entity* _ents
     TokenC _empty_token
+    RingBufferC _hist
     int length
     int offset
     int _s_i
@@ -37,6 +55,7 @@ cdef cppclass StateC:
         this.shifted = <bint*>calloc(length + (PADDING * 2), sizeof(bint))
         this._sent = <TokenC*>calloc(length + (PADDING * 2), sizeof(TokenC))
         this._ents = <Entity*>calloc(length + (PADDING * 2), sizeof(Entity))
+        memset(&this._hist, 0, sizeof(this._hist))
         this.offset = 0
         cdef int i
         for i in range(length + (PADDING * 2)):
@@ -271,7 +290,14 @@ cdef cppclass StateC:
         sig[8] = this.B_(0)[0]
         sig[9] = this.E_(0)[0]
         sig[10] = this.E_(1)[0]
-        return hash64(sig, sizeof(sig), this._s_i)
+        return hash64(sig, sizeof(sig), this._s_i) \
+             + hash64(<void*>&this._hist, sizeof(RingBufferC), 1)
+
+    void push_hist(int act) nogil:
+        ring_push(&this._hist, act)
+
+    int get_hist(int i) nogil:
+        return ring_get(&this._hist, i)
 
     void push() nogil:
         if this.B(0) != -1:
diff --git a/spacy/syntax/stateclass.pyx b/spacy/syntax/stateclass.pyx
index 228a3ff91..9c179820c 100644
--- a/spacy/syntax/stateclass.pyx
+++ b/spacy/syntax/stateclass.pyx
@@ -4,6 +4,7 @@ from __future__ import unicode_literals
 
 from libc.string cimport memcpy, memset
 from libc.stdint cimport uint32_t, uint64_t
+import numpy
 
 from ..vocab cimport EMPTY_LEXEME
 from ..structs cimport Entity
@@ -38,6 +39,13 @@ cdef class StateClass:
     def token_vector_lenth(self):
         return self.doc.tensor.shape[1]
 
+    @property
+    def history(self):
+        hist = numpy.ndarray((8,), dtype='i')
+        for i in range(8):
+            hist[i] = self.c.get_hist(i+1)
+        return hist
+
     def is_final(self):
         return self.c.is_final()