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PERF: Refactor bezier poly coefficient calcs for speedup #31059

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Merged
QuLogic merged 2 commits into from
Feb 3, 2026
Merged

PERF: Refactor bezier poly coefficient calcs for speedup #31059

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2eeaa51
Refactor bezier poly coefficient calcs for speedup
scottshambaugh Jan 20, 2026
9510762
Rework imports
scottshambaugh Feb 3, 2026
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32 changes: 18 additions & 14 deletions lib/matplotlib/bezier.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,23 @@
from matplotlib import _api


# same algorithm as 3.8's math.comb
@np.vectorize
@lru_cache(maxsize=128)
def _comb(n, k):
if k > n:
return 0
k = min(k, n - k)
i = np.arange(1, k + 1)
return np.prod((n + 1 - i)/i).astype(int)
@lru_cache(maxsize=16)
def _get_coeff_matrix(n):
"""
Compute the matrix for converting Bezier control points to polynomial
coefficients for a curve of degree n.

The matrix M is such that M @ control_points gives polynomial coefficients.
Entry M[j, i] = C(n, j) * (-1)^(i+j) * C(j, i) where C is the binomial
coefficient.
"""
def _comb(n, k):
return np.vectorize(math.comb)(n, k)

j = np.arange(n + 1)[:, None]
i = np.arange(n + 1)[None, :] # _comb is non-zero for i <= j
prefactor = (-1) ** (i + j) * _comb(j, i) # j on axis 0, i on axis 1
return (_comb(n, j) * prefactor).astype(float)


class NonIntersectingPathException(ValueError):
Expand Down Expand Up @@ -279,11 +287,7 @@ def polynomial_coefficients(self):
if n > 10:
warnings.warn("Polynomial coefficients formula unstable for high "
"order Bezier curves!", RuntimeWarning)
P = self.control_points
j = np.arange(n+1)[:, None]
i = np.arange(n+1)[None, :] # _comb is non-zero for i <= j
prefactor = (-1)**(i + j) * _comb(j, i) # j on axis 0, i on axis 1
return _comb(n, j) * prefactor @ P # j on axis 0, self.dimension on 1
return _get_coeff_matrix(n) @ self.control_points

def axis_aligned_extrema(self):
"""
Expand Down
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