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Old 2010-04-08, 11:37   #1
ATH
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Default Old pentium bug still alive?

Found this in a public register in Denmark which lists who owns houses and apartments. This apartment is owned by 3 people each owning 1/3.
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Old 2010-04-08, 11:39   #2
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33.33+33.34+33.33=100

Looks fine to me.
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Old 2010-04-08, 14:59   #3
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Yes but it isn't 33.34 its 33.339999999999996 like the old pentium bug:

http://www.trnicely.net/pentbug/bugmail1.html
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Old 2010-04-08, 15:22   #4
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Quote:
Originally Posted by ATH View Post
Yes but it isn't 33.34 its 33.339999999999996 like the old pentium bug:
No, it is just a precision error when trying to print too many significant figures from a double sized value.
Code:
0x4040AB851EB851EB = 33.3399999999999963
0x4040AB851EB851EC = 33.3400000000000034

Last fiddled with by retina on 2010-04-08 at 15:30 Reason: Add binary double equivalents
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Old 2010-04-08, 16:47   #5
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Quote:
Originally Posted by ATH View Post
Yes but it isn't 33.34 its 33.339999999999996 like the old pentium bug:

http://www.trnicely.net/pentbug/bugmail1.html
Such errors, as explained by retina, have been occurring since before Intel was a well-known name. I recall having fun with them (excessive precision from floating-point values) on an IBM 7094 in 1966. Note that .04 is presented as .039999999999996 -- that's the pattern of all such excessive-precision errors: correctdigit-1, followed by several 9's.

The Pentium bug's characteristics were different.

As Nicely wrote in that famous memo, the Pentium bug showed up on calculations like 1/824633702441.0


They didn't cause (correctdigit-1, followed by several 9's) errors.

Last fiddled with by cheesehead on 2010-04-08 at 16:56
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Old 2010-04-08, 17:31   #6
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Who needs 17 digits for that webpage anyway? With 17 digits you could individually number every square the size of ~ 40µm x 40µm over the entire Earth's land surface.
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Old 2010-04-09, 18:56   #7
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I think you got your maths wrong there. With 17 digits you can count to 1017. The surface area of each is about 148,300,000 km2 . Let us round it to 1.5*108 km2. Now 1 km2 is 106 m2. So you get 1.5*1014 m2 = 1.5*1018 cm2. So you get squares of cm2. I think when you converted down from km2 you forgot to double the factor conversion.
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Old 2010-04-09, 23:15   #8
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148,000,000km2
= ~ 12,000km x 12,000km
= ~ 12,000,000m x 12,000,000m
= ~ 300,000,000,000 (of 40µm) x 300,000,000,000 (of 40µm)
= ~ 1023 (of 40µm)2

I don't know what happened there. Forget about the 40µm nonsense I posted above.

Okay, so enough to count each 4cm x 4cm square. Thanks for the correction.
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Old 2010-04-14, 00:48   #9
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1023 / 1017 = One Million.

I think your avatar got the best of you
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