[Maxima] Test suite failures with cvs version?
raymond.toy at ericsson.com
Mon Oct 27 16:03:27 CDT 2008
Dieter Kaiser wrote:
> Hello Ray,
> It seems to me that I am a bit tired. Again I was too fast. I did the check for
> conjugate values with different algorithm and not with conjugate values.
> Now I arrived at this routine:
> (defun expintegral-ei (z)
> (- (expintegral-e 1 (- z)))
> ; (- (* 0.5 (- (log z) (log (/ 1 z)))) (log (- z)))
I think we need to decide what the value of the above expression is.
For z = -r (r real, r > 0), I have
1/2*(log(z)-log(1/z)) - log(-z)
= 1/2*(log(r)+%i*%pi-log(1/r)-%i*%pi) - log(r)
= 1/2*(2*log(r)) - log(r)
For all other z = r*exp(%i*theta), maxima says:
This doesn't match what your code does because you sometimes use %i*%pi
Maybe the real issue is that expintegral_e is computing the wrong value
for negative z?
What definition are you using for Ei and En?
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