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Manuscript Title: A code to evaluate modified Bessel functions based on the continued
fraction method. | ||

Authors: J. Segura, P. Fernandez de Cordoba, Yu.L. Ratis | ||

Program title: BESSIMIN, BESSIMSE | ||

Catalogue identifier: ADGM_v1_0Distribution format: gz | ||

Journal reference: Comput. Phys. Commun. 105(1997)263 | ||

Programming language: Fortran. | ||

Computer: VAX 6410. | ||

Operating system: VAX/VMS, UNIX. | ||

Word size: 32 | ||

Keywords: General purpose, Modified, Bessel functions, Continued fraction, Method. | ||

Classification: 4.7. | ||

Nature of problem:We include two codes in order to evaluate: (1) Modified Spherical Bessel function (subroutine BESSIMSE) (2) Modified Bessel functions of integral order (subroutine BESSIMIN). Both codes evaluate Modified Bessel functions from the lower (positive) orders to a maximum order NMAX in the same run. | ||

Solution method:We have developed a fast code to calculate modified Bessel functions of integral and half-integral order based on continued fractions. This algorithm is specially useful in the case of Bessel functions of high order because it does not require any recalculation using normalization relations. | ||

Restrictions:The maximum order that can be reached with our method, for a fixed real positive value of x, is provided by the maximum real number defined in our machine. The maximum x is limited by the same kind of restriction; however the overflow problem for high x can be eliminated by factoring out e**x for the K's and e**-x for the I's (see text (LONG WRITE-UP: section 5)). | ||

Running time:See text (LONG WRITE-UP: section 5) |

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