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

Write a short note on pointer declaration, Write a short note on pointer de...

Write a short note on pointer declaration A simple variable in a program is stored in a certain number of bytes at a particular memory location, or address, in the machine. Poi

Instruction set architecture, Question (a) A 500 MHz Pentium III proce...

Question (a) A 500 MHz Pentium III processor takes 2 ms to run a program with 200,000 instructions. A 300 MHz UltraSparc processor takes 1.8 ms to run the same program with 23

State about the firewalls - intranet, Firewalls While getting one fire...

Firewalls While getting one firewall for the company's Intranet it should be well known that firewalls come in both hardware and software forms, and that even though all firew

Call a screen as dialog box, The Syntex used to call a screen as dialog box...

The Syntex used to call a screen as dialog box (pop up)is CALL SCREEN STARTING AT ENDING AT

Perform on occurrence of an interrupt, Q. Perform on occurrence of an inter...

Q. Perform on occurrence of an interrupt? Determining these requirements let's work out steps that CPU should perform on occurrence of an interrupt. The CPU should find

Determine signed binary number, -8 is equal to which signed binary number ?...

-8 is equal to which signed binary number ? Ans. 10001000 is the signed binary number that equal to - 8.   To show negative numbers in the binary system, Digit 1 is utilized fo

What are user threads, What are User threads   User threads are support...

What are User threads   User threads are supported above the kernel and are executed by a thread library at the user level. Thread creation & scheduling are done in the user sp

Offset litho duplicating of information, Offset Litho Duplicating Equi...

Offset Litho Duplicating Equipment Required Duplicator Plate-making equipment (not always, essential), e.g. printing box and processing unit Plates Paper Ink

Ms access database to a present conversion, I have converted my MS Access d...

I have converted my MS Access database to a present conversion. I am getting conversion errors? Ans) Design specs have changed in new releases of MS Access. Visit the on-line

How to get the column count of a report, How to get the column count of a r...

How to get the column count of a report? SY-LINSZ system variable gives the column count (line size) and SY-LINCT for line count.

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