Date: Thu, 25 Feb 2010 15:53:03 -0800 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: freebsd-hackers@freebsd.org Subject: Nasty bug in jn(3) Message-ID: <20100225235303.GA28105@troutmask.apl.washington.edu>
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There's a nasty little bug lurking in jn(3). #include <stdio.h> #include <math.h> int main(void) { double z; int i, n; z = 2.4048255576957729; for (n = 2; n < 10; n++) printf("%d %e\n", n, jn(n,z)); return (0); } troutmask:kargl[446] cc -o z testjn.c -lm troutmask:kargl[447] ./z 2 4.317548e-01 3 -inf 4 4.069027e-02 5 -inf 6 3.247664e-03 7 -inf 8 7.495602e-05 9 -inf I can assure you that -inf is not a valid value for an integer order Bessel function at z = 2.40482555... A quick inspection of e_jn.c suggest a similar problem maybe found at other zeros of j0(x). -- Steve
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