86 lines
2.5 KiB
Cython
86 lines
2.5 KiB
Cython
# Author: Lars Buitinck
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# License: BSD 3 clause
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import array
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from cpython cimport array
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cimport cython
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from libc.stdlib cimport abs
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cimport numpy as np
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import numpy as np
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from ..externals.six import string_types
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from sklearn.utils.murmurhash cimport murmurhash3_bytes_s32
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np.import_array()
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@cython.boundscheck(False)
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@cython.cdivision(True)
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def transform(raw_X, Py_ssize_t n_features, dtype):
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"""Guts of FeatureHasher.transform.
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Returns
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-------
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n_samples : integer
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indices, indptr, values : lists
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For constructing a scipy.sparse.csr_matrix.
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"""
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assert n_features > 0
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cdef np.int32_t h
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cdef double value
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cdef array.array indices
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cdef array.array indptr
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indices = array.array("i")
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indptr = array.array("i", [0])
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# Since Python array does not understand Numpy dtypes, we grow the indices
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# and values arrays ourselves. Use a Py_ssize_t capacity for safety.
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cdef Py_ssize_t capacity = 8192 # arbitrary
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cdef np.int32_t size = 0
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cdef np.ndarray values = np.empty(capacity, dtype=dtype)
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for x in raw_X:
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for f, v in x:
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if isinstance(v, string_types):
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f = "%s%s%s" % (f, '=', v)
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value = 1
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else:
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value = v
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if value == 0:
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continue
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if isinstance(f, unicode):
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f = f.encode("utf-8")
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# Need explicit type check because Murmurhash does not propagate
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# all exceptions. Add "except *" there?
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elif not isinstance(f, bytes):
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raise TypeError("feature names must be strings")
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h = murmurhash3_bytes_s32(f, 0)
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array.resize_smart(indices, len(indices) + 1)
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indices[len(indices) - 1] = abs(h) % n_features
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value *= (h >= 0) * 2 - 1
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values[size] = value
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size += 1
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if size == capacity:
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capacity *= 2
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# can't use resize member because there might be multiple
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# references to the arrays due to Cython's error checking
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values = np.resize(values, capacity)
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array.resize_smart(indptr, len(indptr) + 1)
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indptr[len(indptr) - 1] = size
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if len(indices):
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indices_a = np.frombuffer(indices, dtype=np.int32)
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else: # workaround for NumPy < 1.7.0
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indices_a = np.empty(0, dtype=np.int32)
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return (indices_a, np.frombuffer(indptr, dtype=np.int32), values[:size])
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