Free42 possible accuracy flaw
03-23-2022, 08:49 AM
Post: #11
 Werner Senior Member Posts: 891 Joined: Dec 2013
RE: Free42 possible accuracy flaw
(03-23-2022 08:05 AM)Thomas Okken Wrote:  Estimate for exactness: take the number of significant digits, that is, the mantissa length minus the number of trailing zeroes, and multiply that by the exponent; if <= 34, use squaring?
That doesn't work for single-digits eg 8^35. And even 11^32 < 1e34
Quote:The estimate doesn't have to be sharp: multiply the mantissa by such a power of 10 that you get the smallest possible integer, then perform the repeated-squaring algorithm, and if the result is < 10^35, fix the exponent and return it, and otherwise, let bid128_pow() do its thing.
Yes, even if you then do some superfluous work. But better that than accuracy loss ;-)
Doesn't the lib have an exact flag, like in the 71B? As long as the result is exact, keep on squaring. Once it isn't, go back and do the normal e^(x*LN(y))
Werner

41CVâ€ ,42S,48GX,49G,DM42,DM41X,17BII,15CE,DM15L,12C,16CE
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 Messages In This Thread Free42 possible accuracy flaw - J-F Garnier - 03-22-2022, 12:33 PM RE: Free42 possible accuracy flaw - Albert Chan - 03-22-2022, 04:31 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-22-2022, 05:18 PM RE: Free42 possible accuracy flaw - Albert Chan - 03-22-2022, 07:11 PM RE: Free42 possible accuracy flaw - J-F Garnier - 03-24-2022, 10:20 AM RE: Free42 possible accuracy flaw - J-F Garnier - 03-24-2022, 07:18 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-22-2022, 05:39 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-22-2022, 07:38 PM RE: Free42 possible accuracy flaw - Werner - 03-23-2022, 07:30 AM RE: Free42 possible accuracy flaw - Thomas Okken - 03-22-2022, 10:08 PM RE: Free42 possible accuracy flaw - J-F Garnier - 03-23-2022, 07:57 AM RE: Free42 possible accuracy flaw - Albert Chan - 03-25-2022, 02:58 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-23-2022, 08:05 AM RE: Free42 possible accuracy flaw - Werner - 03-23-2022 08:49 AM RE: Free42 possible accuracy flaw - Thomas Okken - 03-23-2022, 12:07 PM RE: Free42 possible accuracy flaw - Albert Chan - 03-24-2022, 04:53 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-23-2022, 06:02 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-23-2022, 07:43 PM RE: Free42 possible accuracy flaw - Albert Chan - 03-23-2022, 07:50 PM RE: Free42 possible accuracy flaw - Albert Chan - 03-23-2022, 09:11 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-24-2022, 11:02 AM RE: Free42 possible accuracy flaw - J-F Garnier - 03-24-2022, 01:02 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-24-2022, 05:01 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-24-2022, 07:45 PM RE: Free42 possible accuracy flaw - Werner - 03-25-2022, 07:03 AM RE: Free42 possible accuracy flaw - J-F Garnier - 03-25-2022, 08:03 AM RE: Free42 possible accuracy flaw - Werner - 03-30-2022, 08:04 AM RE: Free42 possible accuracy flaw - Albert Chan - 03-30-2022, 11:51 PM RE: Free42 possible accuracy flaw - Thomas Okken - 03-25-2022, 08:35 AM RE: Free42 possible accuracy flaw - Albert Chan - 03-27-2022, 10:58 PM RE: Free42 possible accuracy flaw - Werner - 03-25-2022, 08:53 AM RE: Free42 possible accuracy flaw - J-F Garnier - 03-25-2022, 11:12 AM RE: Free42 possible accuracy flaw - Thomas Okken - 03-25-2022, 09:06 AM RE: Free42 possible accuracy flaw - Thomas Okken - 03-25-2022, 09:18 AM

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