Hill Climbing Algorithm in Artificial Intelligence

Presentation
on
By
BHARAT BHUSHAN
Asst. Professor, Department of Computer Sc.
RLSY College, Ranchi
Buddha Science and Technical Institute, Ranchi
www.bharatsir.com
Hill Climbing & Its Variations
Artificial Intelligence

www.bharatsir.com || Mo No : 09835376044 || WhtasApp : 09006365889
Hill - Climbing
A hill-climbing algorithm is an Artificial
Intelligence (AI) algorithm that increases in
value continuously until it achieves a peak
solution.
This algorithm is used to optimize
mathematical problems and in other real-
life applications like marketing and job
scheduling.

Hill - Climbing
It is also called greedy local search as it only
looks to its good immediate neighbor state and not
beyond that.
A node of hill climbing algorithm has two
components which are state and value.
Hill climbing algorithm is a technique which is
used for optimizing the mathematical problems.
One of the widely discussed examples of Hill
climbing algorithm is Traveling-salesman
Problem in which we need to minimize the
distance traveled by the salesman.

Features of Hill Climbing
Following are some main features of Hill Climbing
Algorithm:
Generate and Test Variant: Hill Climbing is the
variant of Generate and Test method. The Generate
and Test method produce feedback which helps to
decide which direction to move in the search space.
Greedy Approach: Hill-climbing algorithm search
moves in the direction which optimizes the cost.
No Backtracking: It does not backtrack the search
space, as it does not remember the previous states.

State-space Diagram for Hill Climbing
The state-space landscape is a graphical representation
of the hill-climbing algorithm which is showing a
graph between various states of algorithm and
Objective

Different regions in the state space landscape:
Local Maximum: Local maximum is a state which is
better than its neighbor states, but there is also another
state which is higher than it.
Global Maximum: Global maximum is the best possible
state of state space landscape. It has the highest value of
objective function.
Current State: It is a state in a landscape diagram where
an agent is currently present.
Flat local maximum: It is a flat space in the landscape
where all the neighbor states of current states have the
same value.
Shoulder: It is a plateau region which has an uphill edge.

Types of Hill Climbing Algorithm:
 Simple Hill Climbing
 Steepest-Ascent Hill-Climbing
 Stochastic Hill Climbing

Simple hill Climbing
Simple hill climbing is the simplest way to implement
a hill climbing algorithm.
It only evaluates the neighbor node state at a time and
selects the first one which optimizes current cost and
set it as a current state.
It only checks it's one successor state, and if it finds
better than the current state, then move else be in the
same state.
This algorithm has the following features:
Less time consuming
Less optimal solution and the solution is not
guaranteed

Algorithm for Simple Hill Climbing
Step 1: Evaluate the initial state, if it is goal state then
return success and Stop.
Step 2: Loop Until a solution is found or there is no
new operator left to apply.
Step 3: Select and apply an operator to the current
state.
Step 4: Check new state:
(a) If it is goal state, then return success and quit.
(b) Else if it is better than the current state then
assign new state as a current state.
(c) Else if not better than the current state, then return
to step2.
Step 5: Exit.

Steepest-Ascent Hill Climbing
The steepest-Ascent algorithm is a variation
of simple hill climbing algorithm. This
algorithm examines all the neighboring
nodes of the current state and selects one
neighbor node which is closest to the goal
state. This algorithm consumes more time as
it searches for multiple neighbors

Algorithm for Steepest-Ascent Hill Climbing
Step 1: Evaluate the initial state, if it is goal state
then return success and stop, else make
current state as initial state.
Step 2: Loop until a solution is found or the current
state does not change.
A. Let SUCC be a state such that any successor of
the current state will be better than it.
B. For each operator that applies to the current
state:

a. Apply the new operator and generate a new
state.
b. Evaluate the new state.
c. If it is goal state, then return it and quit, else
compare it to the SUCC.
d. If it is better than SUCC, then set new state
as SUCC.
e. If the SUCC is better than the current state,
then set current state to SUCC.
Step 5: Exit.

Stochastic Hill Climbing
It does not examine all the neighboring nodes
before deciding which node to select. It just
selects a neighboring node at random and
decides (based on the amount of improvement
in that neighbor) whether to move to that
neighbor or to examine another.
• Evaluate the initial state. If it is a goal state
then stop and return success. Otherwise,
make the initial state the current state.

• Repeat these steps until a solution is found
or the current state does not change.
 Select a state that has not been yet
applied to the current state.
 Apply the successor function to the
current state and generate all the
neighbor states.
 Among the generated neighbor states
which are better than the current state
choose a state randomly.

 If the chosen state is the goal state, then
return success, else make it the current state
and repeat step 2 of the second point.
• Exit from the function.

Application of Hill Climbing
Hill Climbing technique can be used to solve
many problems, where the current state allows
for an accurate evaluation function, such as
1. Network-Flow
2. Travelling Salesman problem
3. 8-Queens problem
4. Integrated Circuit design, etc.
Hill Climbing is used in inductive learning
methods too.

Advantages of Hill Climbing
1. Hill Climbing can be used in continuous as
well as domains.
2. These technique is very useful in job shop
scheduling, automatic programming, circuit
designing, and vehicle routing.
3. It is also helpful to solve pure optimization
problems where the objective is to find the
best state according to the objective
function.

Disadvantages of Hill Climbing
A hill-climbing algorithm which never
makes a move towards a lower value
guaranteed to be incomplete because it can
get stuck on a local maximum. And if
algorithm applies a random walk, by
moving a successor, then it may complete
but not efficient.

Bharat Bhushan, Assistant Professor, RLSY College, Ranchi

Hill Climbing Algorithm in Artificial Intelligence

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