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

Threads model - parallel programming model, In this model a one process can...

In this model a one process can have multiple, concurrent implementations paths. The major programs are scheduled to run by the native operating system. It loads and obtains all th

Show SNMPs representation in ASN.1 syntax, An SNMP integer whose value is 2...

An SNMP integer whose value is 200 has to be transmitted. Show its representation in ASN.1 syntax. An ASN.1 transfer syntax describes how values of ASN.1 types are unambiguousl

Illustrate the logical view of a system, Illustrate the Logical view of a s...

Illustrate the Logical view of a system The Logical view of a system serves to describe existence and meaning of key abstractions and mechanism which form problem space, or wh

Function wallsintact, We also need to know, given a cell, which of its neig...

We also need to know, given a cell, which of its neighbours has all of its walls intact. Write the function wallsintact that accepts the grid and a list of neighbouring cells and r

Discuss in detail about micro computer, Discuss in detail about Micro compu...

Discuss in detail about Micro computer A microcomputer's CPU is a microprocessor. The microcomputer was originated in late 1970s. The first microcomputer was built around 8-bit

How to changing the directory in dos, Q. How to Changing the Directory in D...

Q. How to Changing the Directory in DOS? You can change the directory. After changing the directory, the new directory becomes the default directory. For example, you change th

Telecommunications, with poisson arrival of two calls per minute what is th...

with poisson arrival of two calls per minute what is the probability that more than three calls will arrive in two minutes? that is the time during which at least 4 calls will arr

How can we access the correction and transport system, How can we access th...

How can we access the correction and transport system? Each time you make a new object or change an existing object in the ABAP/4 Dictionary, you branch automatically to the W

What is an compiled languages, What is an compiled languages In compile...

What is an compiled languages In compiled languages the instructions into machine code and kept them  in a separate file for later implementation. Many modern compilers can com

Design a circuit which computes the square of a number, Design a circuit wh...

Design a circuit which computes the square of a number? This should not make use of any multiplier circuits. This should use Multiplexers and some other logic as: 1^2=0+1=1

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