Arc consistency, Computer Engineering

Assignment Help:

Arc Consistency:

There have been many advances in how constraint solvers search for solutions (remember this means an assignment of a value to each variable in such a way thatno constraint is broken). We look first at a pre-processing step which can greatly improve efficiency by pruning the search space, namely arc-consistency. Following this, we'll look at two search methods, backtracking and forward checking which keep assigning values to variables until a solution is found. Finally, we'll look at some heuristics for improving the efficiency of the solver, namely how to order the choosing of the variables, and how to order the assigning of the values to variables. 

The pre-processing routine for bianry constraints known as  arc-consistency involves calling a pair (xi, xj) an arc and noting that this is an ordered pair, i.e., it is not the same as (xj, xi). Each arc is associated with a single constraint Cij, which constrains variables xi  and xj. We say that the arc (xi, xj) is  consistent  if, for all values a in Di, there is a value b in Dj  such that the assignment xi=a and xj=b satisfies constraint Cij. Note that (xi, xj) being consistent doesn't necessarily mean that (xj,xi) is also consistent. To use this in a pre-processing way, we take every pair of variables and make it arc-consistent. That is, we take each pair (xi,xj) and remove variables from Di  which make it inconsistent, until it becomes consistent. This effectively removes values from the domain of variables, hence prunes the search space and makes it likely that the solver will succeed (or fail to find a solution) more quickly.


Related Discussions:- Arc consistency

Define electronic data interchange, Electronic Data Interchange (EDI ) is u...

Electronic Data Interchange (EDI ) is used by companies for transactions that happen on regular basis to a pre-determined format. It is one of the electronic commerce technologies.

What are the attributes of the method, What are the attributes of the metho...

What are the attributes of the method? During implementation a process is characterized by various attributes maintain by the system: Its state Its identification

How many types of stages include in process of data mining, How many types ...

How many types of stages include in process of data mining? The process of data mining comprised three stages as given below: a) The initial exploration b) Model buildin

Compare a decoder and a demultiplexer with block diagram, Compare a decoder...

Compare a decoder and a demultiplexer with suitable block diagrams. Ans. Demultiplexer has similar circuit as decoder but here e is obtained as the particular input line, the

Neural network for two predictors thickness, 2) Consider the following neur...

2) Consider the following neural network for two predictors Thickness and Alignment and two classes Print Quality High and Low. Some weights are shown in the table, including weigh

Explain the drawback of top down parsing of backtracking, Write down the dr...

Write down the drawback of top down parsing of backtracking. Following are disadvantages of top down parsing of backtracking: (i) Semantic actions can't be performed whereas

Explain the edge-triggered j-k flip-flop, Explain the Edge-triggered J-K fl...

Explain the Edge-triggered J-K flip-flop? The J-K flip-flop works extremely similar to S-R flip-flop. The merely difference is that this flip-flop has NO invalid state.

Design odd-even transposition algorithm, Q. Design Odd-Even Transposition A...

Q. Design Odd-Even Transposition Algorithm? Algorithm: Odd-Even Transposition for I=1 to N     {            If (I%2 != 0) //i.e. Odd phase            {

Analog to Digital convertor, The A/D converter whose conversion time is ind...

The A/D converter whose conversion time is independent of the number of bits is ? Ans. Parallel conversion is the A/D converter whose conversion time is independent of the Numbe

When is a memory unit called as ram, When is a memory unit called as RAM? ...

When is a memory unit called as RAM? A memory unit is called as RAM if any location can be accessed for a read or writes operation in some fixed quantity of time that is indepe

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd