I doubt this is a new issue. The underlying arithmetic is IEEE 754.
Floating point numbers have the following problems (at least):
- addition is not associative
- not all decimal numbers within the range of representable numbers are
representable exactly
Basically, it is rarely justifiable to test for equality of doubles.
Edward
On 3/4/14 11:21 AM, Matt Jones wrote:
Daniel and Christopher --
Do either of you have any insight into this new rounding issue? Can
you confirm whether or not this is new behavior?
Matt
---------- Forwarded message ----------
From: <[email protected] <mailto:[email protected]>>
Date: Tue, Mar 4, 2014 at 3:24 AM
Subject: [Kepler - Bug #6439] (New) Double rounding fails in some
cases while evaluating Expressions
To:
Issue #6439 has been reported by Owsiak Michal.
------------------------------------------------------------------------
Bug #6439: Double rounding fails in some cases while evaluating
Expressions <https://projects.ecoinformatics.org/ecoinfo/issues/6439>
* Author: Owsiak Michal
* Status: New
* Priority: Urgent
* Assignee: Derik Barseghian
* Category: actors
* Target version: 2.3.0
* Bugzilla-Id:
It seems that addition of doubles can produce values slightly
different than they should to be.
Please take a look at attached workflow (simple_error.xml).
Condition that should be satisfied to escape the loop is: 1.7 > 1.5 + 0.1
However, loop is interrupted sooner, because of incorrect calculation
of doubles. Value of "p" is set to: 1.6000000000000003
This, of course, makes it impossible to use doubles as check points
for the loops.
However, it seems that casting to string and back works fine (take a
look at second workflow - simple.xml)
Cheers
Michal
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