| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354 |
- """Precompute the polynomials for the asymptotic expansion of the
- generalized exponential integral.
- Sources
- -------
- [1] NIST, Digital Library of Mathematical Functions,
- https://dlmf.nist.gov/8.20#ii
- """
- import os
- try:
- import sympy
- from sympy import Poly
- x = sympy.symbols('x')
- except ImportError:
- pass
- def generate_A(K):
- A = [Poly(1, x)]
- for k in range(K):
- A.append(Poly(1 - 2*k*x, x)*A[k] + Poly(x*(x + 1))*A[k].diff())
- return A
- WARNING = """\
- /* This file was automatically generated by _precompute/expn_asy.py.
- * Do not edit it manually!
- */
- """
- def main():
- print(__doc__)
- fn = os.path.join('..', 'cephes', 'expn.h')
- K = 12
- A = generate_A(K)
- with open(fn + '.new', 'w') as f:
- f.write(WARNING)
- f.write("#define nA {}\n".format(len(A)))
- for k, Ak in enumerate(A):
- tmp = ', '.join([str(x.evalf(18)) for x in Ak.coeffs()])
- f.write("static const double A{}[] = {{{}}};\n".format(k, tmp))
- tmp = ", ".join(["A{}".format(k) for k in range(K + 1)])
- f.write("static const double *A[] = {{{}}};\n".format(tmp))
- tmp = ", ".join([str(Ak.degree()) for Ak in A])
- f.write("static const int Adegs[] = {{{}}};\n".format(tmp))
- os.rename(fn + '.new', fn)
- if __name__ == "__main__":
- main()
|
