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From: Gautier write-only <gautier_niouzes@hotmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Cannot summate small float values
Date: Sun, 21 Nov 2010 17:23:17 -0800 (PST)
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On 21 nov, 22:06, tolkamp wrote:

> Thank you your reaction.
> Using your procedure Sums I found out that when the start value of X <
> 0.24 the summation works correct with Dx = 1.0E-8
> When start X > 0.25 the summation remains 0.250000000.

Anyway, since Dx is constant, you should never add it over and over:
it will accumulate numerical errors (with very rare exceptions) even
if it looks to work correctly on a few iterations.
The right way is
  X:= N * Real(Dx);
  N:= N + 1;
where Real is your floating-point type.
Cheers
______________________________________________________________
Gautier's Ada programming -- http://gautiersblog.blogspot.com/
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