76 lines
2.1 KiB
C
76 lines
2.1 KiB
C
/*
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bessel_polynomial.h
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Copyright (C) 2011 and later Lubomir I. Ivanov (neolit123 [at] gmail)
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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/*
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algorithm to calculate coefficients for a bessel polynomial from krall & fink
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series.
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*/
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#ifndef _BESSEL_POLYNOMIAL_H_
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#define _BESSEL_POLYNOMIAL_H_
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#include "custom_math.h"
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#include "factorial.h"
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#ifdef _BESSEL_USE_INLINE_
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#define _BESSEL_INLINE _CMATH_INLINE
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#else
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#define _BESSEL_INLINE
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#endif
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#ifndef _CMATH_ANSI
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#define _BESSEL_MAX_ORDER 10
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#else
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#define _BESSEL_MAX_ORDER 3
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#endif
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/* return a coefficient */
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_BESSEL_INLINE cmath_std_int_t
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bessel_coefficient(const cmath_uint16_t k, const cmath_uint16_t n)
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{
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register cmath_std_int_t c;
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const cmath_uint16_t nmk = (cmath_uint16_t)(n - k);
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c = factorial(2*n - k);
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c /= (factorial(nmk)*factorial(k)) * (1 << nmk);
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return c;
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}
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/* calculate all coefficients for n-th order polynomial */
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_BESSEL_INLINE
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void bessel_polynomial( cmath_std_int_t *coeff,
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const cmath_uint16_t order,
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const cmath_uint16_t reverse )
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{
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register cmath_uint16_t i = (cmath_uint16_t)(order + 1);
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if (reverse)
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{
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while (i--)
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coeff[order-i] = bessel_coefficient(i, order);
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}
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else
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{
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while (i--)
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coeff[i] = bessel_coefficient(i, order);
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}
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}
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#endif /* _BESSEL_POLYNOMIAL_H */
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