Parser StateC optimizations (#10746)

* `StateC`: Optimizations

Avoid GIL acquisition in `__init__`
Increase default buffer capacities on init
Reduce C++ exception overhead

* Fix typo

* Replace `set::count` with `set::find`

* Add exception attribute to c'tor

* Remove unused import

* Use a power-of-two value for initial capacity
Use default-insert to init `_heads` and `_unshiftable`

* Merge `cdef` variable declarations and assignments

spacy/pipeline/_parser_internals/_state.pxd

@@ -6,7 +6,6 @@ cimport libcpp
 from libcpp.unordered_map cimport unordered_map
 from libcpp.vector cimport vector
 from libcpp.set cimport set
-from cpython.exc cimport PyErr_CheckSignals, PyErr_SetFromErrno
 from murmurhash.mrmr cimport hash64
 
 from ...vocab cimport EMPTY_LEXEME
@@ -26,7 +25,7 @@ cdef struct ArcC:
 
 
 cdef cppclass StateC:
-    int* _heads
+    vector[int] _heads
     const TokenC* _sent
     vector[int] _stack
     vector[int] _rebuffer
@@ -41,25 +40,27 @@ cdef cppclass StateC:
     int offset
     int _b_i
 
-    __init__(const TokenC* sent, int length) nogil:
+    __init__(const TokenC* sent, int length) nogil except +:
+        this._heads.resize(length, -1)
+        this._unshiftable.resize(length, False)
+
+        # Reserve memory ahead of time to minimize allocations during parsing.
+        # The initial capacity set here ideally reflects the expected average-case/majority usage.
+        cdef int init_capacity = 32
+        this._stack.reserve(init_capacity)
+        this._rebuffer.reserve(init_capacity)
+        this._ents.reserve(init_capacity)
+        this._left_arcs.reserve(init_capacity)
+        this._right_arcs.reserve(init_capacity)
+        this.history.reserve(init_capacity)
+
         this._sent = sent
-        this._heads = <int*>calloc(length, sizeof(int))
-        if not (this._sent and this._heads):
-            with gil:
-                PyErr_SetFromErrno(MemoryError)
-                PyErr_CheckSignals()
         this.offset = 0
         this.length = length
         this._b_i = 0
-        for i in range(length):
-            this._heads[i] = -1
-            this._unshiftable.push_back(0)
         memset(&this._empty_token, 0, sizeof(TokenC))
         this._empty_token.lex = &EMPTY_LEXEME
 
-    __dealloc__():
-        free(this._heads)
-
     void set_context_tokens(int* ids, int n) nogil:
         cdef int i, j
         if n == 1:
@@ -132,19 +133,20 @@ cdef cppclass StateC:
                 ids[i] = -1
 
     int S(int i) nogil const:
-        if i >= this._stack.size():
+        cdef int stack_size = this._stack.size()
+        if i >= stack_size or i < 0:
             return -1
-        elif i < 0:
+        else:
-            return -1
+            return this._stack[stack_size - (i+1)]
-        return this._stack.at(this._stack.size() - (i+1))
 
     int B(int i) nogil const:
+        cdef int buf_size = this._rebuffer.size()
         if i < 0:
             return -1
-        elif i < this._rebuffer.size():
+        elif i < buf_size:
-            return this._rebuffer.at(this._rebuffer.size() - (i+1))
+            return this._rebuffer[buf_size - (i+1)]
         else:
-            b_i = this._b_i + (i - this._rebuffer.size())
+            b_i = this._b_i + (i - buf_size)
             if b_i >= this.length:
                 return -1
             else:
@@ -243,7 +245,7 @@ cdef cppclass StateC:
             return 0
         elif this._sent[word].sent_start == 1:
             return 1
-        elif this._sent_starts.count(word) >= 1:
+        elif this._sent_starts.const_find(word) != this._sent_starts.const_end():
             return 1
         else:
             return 0
@@ -328,7 +330,7 @@ cdef cppclass StateC:
         if item >= this._unshiftable.size():
             return 0
         else:
-            return this._unshiftable.at(item)
+            return this._unshiftable[item]
 
     void set_reshiftable(int item) nogil:
         if item < this._unshiftable.size():
@@ -348,6 +350,9 @@ cdef cppclass StateC:
         this._heads[child] = head
 
     void map_del_arc(unordered_map[int, vector[ArcC]]* heads_arcs, int h_i, int c_i) nogil:
+        cdef vector[ArcC]* arcs
+        cdef ArcC* arc
+
         arcs_it = heads_arcs.find(h_i)
         if arcs_it == heads_arcs.end():
             return
@@ -356,12 +361,12 @@ cdef cppclass StateC:
         if arcs.size() == 0:
             return
 
-        arc = arcs.back()
+        arc = &arcs.back()
         if arc.head == h_i and arc.child == c_i:
             arcs.pop_back()
         else:
             for i in range(arcs.size()-1):
-                arc = arcs.at(i)
+                arc = &deref(arcs)[i]
                 if arc.head == h_i and arc.child == c_i:
                     arc.head = -1
                     arc.child = -1
@@ -401,7 +406,7 @@ cdef cppclass StateC:
         this._rebuffer = src._rebuffer
         this._sent_starts = src._sent_starts
         this._unshiftable = src._unshiftable
-        memcpy(this._heads, src._heads, this.length * sizeof(this._heads[0]))
+        this._heads = src._heads
         this._ents = src._ents
         this._left_arcs = src._left_arcs
         this._right_arcs = src._right_arcs