65 lines
1.6 KiB
Cython
65 lines
1.6 KiB
Cython
"""
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The :mod:`sklearn.utils.arrayfuncs` module includes a small collection of auxiliary
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functions that operate on arrays.
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"""
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from cython cimport floating
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from libc.math cimport fabs
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from libc.float cimport DBL_MAX, FLT_MAX
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from ._cython_blas cimport _copy, _rotg, _rot
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def min_pos(const floating[:] X):
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"""Find the minimum value of an array over positive values
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Returns the maximum representable value of the input dtype if none of the
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values are positive.
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"""
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cdef Py_ssize_t i
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cdef floating min_val = FLT_MAX if floating is float else DBL_MAX
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for i in range(X.size):
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if 0. < X[i] < min_val:
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min_val = X[i]
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return min_val
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# General Cholesky Delete.
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# Remove an element from the cholesky factorization
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# m = columns
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# n = rows
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#
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# TODO: put transpose as an option
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def cholesky_delete(floating[:, :] L, int go_out):
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cdef:
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int n = L.shape[0]
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int m = L.strides[0]
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floating c, s
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floating *L1
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int i
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if floating is float:
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m /= sizeof(float)
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else:
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m /= sizeof(double)
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# delete row go_out
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L1 = &L[0, 0] + (go_out * m)
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for i in range(go_out, n-1):
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_copy(i + 2, L1 + m, 1, L1, 1)
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L1 += m
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L1 = &L[0, 0] + (go_out * m)
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for i in range(go_out, n-1):
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_rotg(L1 + i, L1 + i + 1, &c, &s)
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if L1[i] < 0:
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# Diagonals cannot be negative
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L1[i] = fabs(L1[i])
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c = -c
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s = -s
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L1[i + 1] = 0. # just for cleanup
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L1 += m
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_rot(n - i - 2, L1 + i, m, L1 + i + 1, m, c, s)
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