jax.numpy.polyval

jax.numpy.polyval(p, x, *, unroll=16)

Evaluate a polynomial at specific values.

LAX-backend implementation of polyval().

The unroll parameter is JAX specific. It does not effect correctness but can have a major impact on performance for evaluating high-order polynomials. The parameter controls the number of unrolled steps with lax.scan inside the polyval implementation. Consider setting unroll=128 (or even higher) to improve runtime performance on accelerators, at the cost of increased compilation time.

Original docstring below.

If p is of length N, this function returns the value:

p[0]*x**(N-1) + p[1]*x**(N-2) + ... + p[N-2]*x + p[N-1]

If x is a sequence, then p(x) is returned for each element of x. If x is another polynomial then the composite polynomial p(x(t)) is returned.

Parameters

• p (array_like or poly1d object) – 1D array of polynomial coefficients (including coefficients equal to zero) from highest degree to the constant term, or an instance of poly1d.

• x (array_like or poly1d object) – A number, an array of numbers, or an instance of poly1d, at which to evaluate p.

Returns

values – If x is a poly1d instance, the result is the composition of the two polynomials, i.e., x is “substituted” in p and the simplified result is returned. In addition, the type of x - array_like or poly1d - governs the type of the output: x array_like => values array_like, x a poly1d object => values is also.

Return type

ndarray or poly1d

References

1

I. N. Bronshtein, K. A. Semendyayev, and K. A. Hirsch (Eng. trans. Ed.), Handbook of Mathematics, New York, Van Nostrand Reinhold Co., 1985, pg. 720.