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Chang_Pai_L_

Beginner

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08-08-2016
06:57 AM

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Question about calculate the Bessel function with IMSL

Ver. Intel Composer XE2013 with Visual Studio 2010 Ultimate

I want to solve the problem about BesselI0/BesselI1 with using the IMSL. Problem is one extreme value divided by another one extreme value and the result should be an uncomplicated value.

Unfortunately, I can not calculate when input data over 700, the output data over 300 order, modified Bessel function of the zero and first kind data will present 'infinite' .

My PROBLEM like (double precision)

'"M(I)=DBSI0(L1(I))/DBSI1(L1(I))"" L1(I) are real data, The "problem" happened in L1(I)>700, the M(I) output "NaN" result.

How could I calculate this vector?

Thanks for any help!!

2 Replies

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mecej4

Black Belt

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08-08-2016
09:21 AM

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See if you can use Hankel's asymptotic expansions for *I*_{0} and *I*_{1} ( https://en.wikipedia.org/wiki/Bessel_function#Asymptotic_forms ). Using those expansions, you can write the ratio *I*_{0}(*z*)/*I*_{1}(*z*) as the ratio of two power series in 1/*z*. The leading factor, *e ^{z}*/sqrt(

For values of *z* with modulus as large as 700, you should be able to obtain accurate results with a small number of terms in the series.

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Chang_Pai_L_

Beginner

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08-09-2016
07:09 PM

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Thanks for useful reply!

For more complete information about compiler optimizations, see our Optimization Notice.