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Re: Strange problem [message #28140 is a reply to message #2626]

Sun, 25 November 2001 17:38

Bhautik Joshi
Messages: 21
Registered: November 2001

Junior Member

> Anybody know what's going on?

My spin on it:

Well, I think it may be a problem that goes right down to the core, and
is not just restricted to FOR loops.

Example:

MOO>a=replicate(0.1,100)
MOO>print, total(a)
10.0000
MOO>print, total(a) - 0.1*100
1.90735e-06

argh! where I think the problem may lie is with the binary
representation of floating point numbers. Now, its been a
loooooooooooooooooooooooong while since I did computer architecture
(yes, it is a real subject at uni) but as far as I remember, in floating
point binary, there is no 'exact' representation for 0.1.

However, lets take 0.5 - which is a quarter of 2; something nice and
(pardon the expression) base-twoish.

MOO>a=replicate(0.5,100)
MOO>print, total(a) - 0.5*100
0.00000

Lets change the game slightly again:

MOO>a=replicate(0.51,100)
MOO>print, total(a) - 0.51*100
-4.95911e-05

should i be worried?

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[Message index]

		strange problem: Alarm Clock????.... By: stl on Tue, 09 August 1994 09:05
		Re: Strange problem By: Pavel A. Romashkin on Mon, 26 November 2001 10:15
		Re: Strange problem By: Andre Kyme on Mon, 26 November 2001 14:04
		Re: Strange problem By: Jeff Hester on Wed, 05 December 2001 07:40
		Re: Strange problem By: Martin Downing on Mon, 26 November 2001 07:00
		Re: Strange problem By: Andre Kyme on Mon, 26 November 2001 14:10
		Re: Strange problem By: Bhautik Joshi on Sun, 25 November 2001 19:55
		Re: Strange problem By: Bhautik Joshi on Sun, 25 November 2001 17:38

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