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## CSP problem MRV can be implemented independently?

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• Hello everyone, I have downloaded AIMA version 2 sample chapter 5 and am doing its exercises. In exercise 5.7, it requires to compare the algorithms of MRV,
Message 1 of 2 , Dec 30, 2003
Hello everyone,
I have downloaded AIMA version 2 sample chapter 5 and am doing its
exercises.

In exercise 5.7, it requires to compare the algorithms of MRV,
forward checking, FC+MRV, Min-conflicts.
But I wonder is it possible to implement MRV independently without FC?
My impossible reasons are as follows:
1. MRV means "minimium remaining values". It means the unassigned
variable with "minimium remaining values" should be selected firstly.
The 2 implementation ideas are
1. to filter unassigned variables' domain everytime after
assigning a variable.
or
2. calculate the every unassigned variable's legal domains
everytime before select.

The above 2nd implemenation is low efficient for repeat calculation
on legal domains, therefore, it is a bad idea.

So only the 1st implementation is accepted. It seems the exercise 5.7
should be modified to "compare the algorithms of FC,FC+MRV,Min-
conflicts.

What's about your idea?

Thank you for your attention.
Best regards/chenyu
• Page 144 of your d/l copy refers to the method of BT + MRV, meaning that FC is not needed. However, they work like hand in glove. At the bottom of the same
Message 2 of 2 , Dec 31, 2003
Page 144 of your d/l copy refers to the method of BT + MRV, meaning
that FC is not needed. However, they work like hand in glove. At the
bottom of the same page, the book says FC is an efficient way to
compute MRV. Otherwise, finding the MRV involves many redundant
computations, as you've noticed.

For a more in-depth explanation, see
http://www.cs.toronto.edu/~fbacchus/Papers/BvRCP95.pdf
and look at pages 6 & 7.

Best regards,
Brandon

--- In aima-talk@yahoogroups.com, "chenyu468" <chenyu468@y...> wrote:
> Hello everyone,
> I have downloaded AIMA version 2 sample chapter 5 and am doing its
> exercises.
>
> In exercise 5.7, it requires to compare the algorithms of MRV,
> forward checking, FC+MRV, Min-conflicts.
> But I wonder is it possible to implement MRV independently without
FC?
> My impossible reasons are as follows:
> 1. MRV means "minimium remaining values". It means the unassigned
> variable with "minimium remaining values" should be selected
firstly.
> The 2 implementation ideas are
> 1. to filter unassigned variables' domain everytime after
> assigning a variable.
> or
> 2. calculate the every unassigned variable's legal domains
> everytime before select.
>
> The above 2nd implemenation is low efficient for repeat calculation
> on legal domains, therefore, it is a bad idea.
>
> So only the 1st implementation is accepted. It seems the exercise
5.7
> should be modified to "compare the algorithms of FC,FC+MRV,Min-
> conflicts.
>
> What's about your idea?
>
>
> Thank you for your attention.
> Best regards/chenyu
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