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123 lines
3.3 KiB
Cython
123 lines
3.3 KiB
Cython
from libcpp.vector cimport vector
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from libc.stdint cimport uint32_t
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from libc.stdint cimport int64_t
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from libc.stdint cimport uint64_t
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import numpy
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cdef struct Node:
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float prob
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int left
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int right
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cdef struct BitArray:
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uint64_t data
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cdef BitArray set_bit(BitArray barray, unsigned char id_) nogil:
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cdef uint64_t one = 1
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barray.data |= one << id_
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return barray
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cdef BitArray clear_bit(BitArray barray, unsigned char id_) nogil:
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cdef uint64_t one = 1
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barray.data ^= one << id_
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return barray
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cpdef uint64_t[:] huffman_encode(float[:] probs):
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assert len(probs) >= 3
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output = numpy.zeros(shape=(len(probs),), dtype=numpy.uint64)
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cdef int size = len(probs)
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cdef vector[Node] nodes
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cdef int i = size - 1
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cdef int j = 0
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append_two(nodes, i, i-1, probs[i] + probs[i-1])
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i -= 2
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append_one(nodes, 0, i, probs[i])
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j += 1
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i -= 1
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while i >= 0 or j < len(nodes):
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if i < 0:
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append_zero(nodes, j)
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j += 2
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elif j >= len(nodes):
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append_two(nodes, i, i-1, probs[i]+probs[i-1])
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elif i >= 1 and (j == len(nodes) or probs[i-1] < nodes[j].prob):
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append_two(nodes, i, i-1, probs[i] + probs[i-1])
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i -= 2
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elif (j+1) < len(nodes) and nodes[j+1].prob < probs[i]:
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append_zero(nodes, j)
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j += 2
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else:
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append_one(nodes, j, i, probs[i])
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i -= 1
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j += 1
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cdef vector[BitArray] codes
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codes.resize(len(probs))
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for i in range(len(probs)):
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codes[i].data = 0
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assign_codes(nodes, codes, len(nodes) - 2, BitArray(data=0), 0)
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output = numpy.zeros(shape=(len(codes),), dtype=numpy.uint64)
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for i in range(len(codes)):
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output[i] = codes[i].data
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return output
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cdef int assign_codes(vector[Node]& nodes, vector[BitArray]& codes, int i,
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BitArray code, int bit) except -1:
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cdef BitArray left_code = clear_bit(code, bit)
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if nodes[i].left >= 0:
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if nodes[i].left != i:
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assign_codes(nodes, codes, nodes[i].left, left_code, bit+1)
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else:
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id_ = -(nodes[i].left + 1)
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codes[id_] = left_code
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cdef BitArray right_code = set_bit(code, bit)
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if nodes[i].right >= 0:
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if nodes[i].right != i:
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assign_codes(nodes, codes, nodes[i].right, right_code, bit+1)
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else:
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id_ = -(nodes[i].right + 1)
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codes[id_] = right_code
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cdef int append_zero(vector[Node]& nodes, int j) nogil:
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cdef Node node
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node.left = j
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node.right = j+1
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node.prob = nodes[j].prob + nodes[j+1].prob
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nodes.push_back(node)
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cdef int append_one(vector[Node]& nodes, int j, int id_, float prob) except -1:
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cdef Node node
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# Encode leaves as negative integers, where the integer is the index of the
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# word in the vocabulary.
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leaf_id = - <int64_t>(id_ + 1)
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new_prob = prob + nodes[j].prob
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if prob < nodes[j].prob:
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node.left = leaf_id
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node.right = j
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node.prob = new_prob
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nodes.push_back(node)
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else:
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node.left = j
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node.right = leaf_id
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node.prob = new_prob
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nodes.push_back(node)
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cdef int append_two(vector[Node]& nodes, int id1, int id2, float prob) except -1:
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cdef Node node
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node.left = -<int64_t>(id1 + 1)
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node.right = -<int64_t>(id2 + 1)
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node.prob = prob
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nodes.push_back(node)
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