Formal solutions and factorization of differential operators with power series coefficients
Journal of Symbolic Computation
Fast evaluation of holonomic functions
Theoretical Computer Science - Special issue on real numbers and computers
Solving difference equations in finite terms
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Fast Multiple-Precision Evaluation of Elementary Functions
Journal of the ACM (JACM)
Fast evaluation of holonomic functions near and in regular singularities
Journal of Symbolic Computation
Around the numeric-symbolic computation of differential Galois groups
Journal of Symbolic Computation
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Time-and space-efficient evaluation of some hypergeometric constants
Proceedings of the 2007 international symposium on Symbolic and algebraic computation
NumGfun: a package for numerical and analytic computation with D-finite functions
Proceedings of the 2010 International Symposium on Symbolic and Algebraic Computation
Stokes phenomenon: graphical visualization and certified computation
Proceedings of the 2011 International Workshop on Symbolic-Numeric Computation
ACM Communications in Computer Algebra
Finding hyperexponential solutions of linear ODEs by numerical evaluation
Proceedings of the 38th international symposium on International symposium on symbolic and algebraic computation
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Let L@?K(z)[@?] be a linear differential operator, where K is the field of algebraic numbers. A holonomic function over K is a solution f to the equation Lf=0. We will also assume that f admits initial conditions in K at a non-singular point z@?K. Given a broken-line path @c=z@?z^' between z and z^', which avoids the singularities of L and with vertices in K, we have shown in a previous paper [van der Hoeven, J., 1999. Fast evaluation of holonomic functions. Theoret. Comput. Sci. 210, 199-215] how to compute n digits of the analytic continuation of f along @c in time O(nlog^3nloglogn). In a second paper [van der Hoeven, J., 2001b. Fast evaluation of holonomic functions near and in singularities. J. Symbolic Comput. 31, 717-743], this result was generalized to the case when z^' is allowed to be a regular singularity, in which case we compute the limit of f when we approach the singularity along @c. In the present paper, we treat the remaining case when the end-point of @c is an irregular singularity. In fact, we will solve the more general problem to compute ''singular transition matrices'' between non-standard points above a singularity and regular points in K near the singularity. These non-standard points correspond to the choice of ''non-singular directions'' in Ecalle's accelero-summation process. We will show that the entries of the singular transition matrices may be approximated up to n decimal digits in time O(nlog^4nloglogn). As a consequence, the entries of the Stokes matrices for L at each singularity may be approximated with the same time complexity.