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- From: "Thomas Zangl - Home" <>
- To: "cgal-discuss" <>
- Subject: Re:[cgal-discuss] Difference between Lazy_exact and Filtered_kernel?
- Date: Sun, 10 Aug 2008 18:09:57 +0200
Am Thu, 03 Jul 2008 15:21:43 +0200, schrieb "Andreas Fabri"
<>:
Hi!
>> Sorry, but I did not get yet what the *main* difference between the
>> Lazy_kernel and Filtered_kernel is.
>
>The main difference is that
>The lazy kernel is exact_predicates_exact_constructions
>The Filtered kernel is only exact_predicates
I tried to summarize your explainations about the lazy kernel and the
DAG of the geometric operations:
If geometric and arithmetic operations are carried out using the exact number
type, the lazy kernel stores a DAG (''directed acyclic graph'') for every
operation. Each node of the DAG stores:
* A geometric object or number with intervals of doubles,
* The type of the geometric or arithmetic operation,
* Pointers to the DAG nodes representing the operands of the
geometric/arithmetic operation.
The DAG for each operation is stored in a history-like way. If a
predicate on the lazy kernel fails, the postponed exact computation is
replayed from the information stored in the DAG. The lazy kernel fails
if e.g., a comparison is performed using Interval arithmetic and the
interval overlaps, hence, the filter cannot securely decide.
-----
However, some questions arise:
-> Is a Geometric object something like a point, line, segment, plane,
triangle?
-> The type of geometric or artihmetic operation is: +,-, etc. or
"intersection(x,y)"?
How are the constructions filtered? Can you please give me an example?
Thank you!
--
,yours Thomas Zangl, Bakk.rer.soc.oec. -
-
- Freelancer - IT Consulting & Software Development -
- Student of Software Development-Economy (Master) -
- http://blog.tzis.net -
- Re:[cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Thomas Zangl - Home, 08/10/2008
- Re: [cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Andreas Fabri, 08/11/2008
- Re:[cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Thomas Zangl - Home, 08/11/2008
- Re: [cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Andreas Fabri, 08/11/2008
- Re:[cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Thomas Zangl - Home, 08/11/2008
- Re: [cgal-discuss] Difference between Lazy_exact and Filtered_kernel?, Andreas Fabri, 08/11/2008
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