SF [2159499] Full bigfloat precision for Gamma after the second call
Subject: SF [2159499] Full bigfloat precision for Gamma after the second call
From: Stavros Macrakis
Date: Tue, 14 Oct 2008 17:30:38 -0400
On Tue, Oct 14, 2008 at 2:03 PM, Raymond Toy <raymond.toy at ericsson.com>wrote:
> Ok, ok. :-)
>
OK, a Maxima-level demo like this is convincing. Thanks.
I think fppi is correct. It's the computation in fppi1 that is
> incorrect because it uses $fpprec instead of fpprec.
>
Try your test case again, with an addition:
zot(z,fpprec):= bfloat(%pi*z/sin(%pi*z))$
fpprec:64$
zot(bfloat(1/2),fpprec)$
fpprec:128$
bfloat(%pi); <<<<<<< fppi returns without calling fppi1 for a new
value of %pi
bfloat(sin(2)) <<<<<<< add this to test; fppi calls fppi1 and gets
correct value
bfloat(%pi); <<<<<<< now gives correct result
So it looks as though the problem is not the pi calculation itself (i.e.
fppi1), but something in the logic of fppi or fpprec1.
-s