AMORTIZED is 0 whereas the actual cost was a

AMORTIZED
ANALYSIS OF A BINARY COUNTER

There
are two types of Binary Counter:

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1.     Aggregate Method

2.     Accounting Method

3.     Potential Method

 

Accounting Method: 

Ø Accounting method in a
amortized analysis is a method which is based on accounting.

Ø It is the easiest way to
calculate the amortized cost of an operation.

Ø It is better than the
aggregate method or potential method.

Ø But this method do not
give us a guarantee of obvious analysis.

Ø This Method does not
include any complexity.

Ø Each operation in this
method is assigned with a amortized cost

Ø The actual cost should be
greater than the amortized cost.

Ø Different amortized costs being
assigned to multiple different amortized operations. Some working contain
amortized cost more or less than the actual cost.

Ø When the cost exceeds from
the actual cost of amortized operation. Then the specific objects is assigned
with a difference in a data structure called credit.

Ø If the amortized cost is
less than the actual cost, then the credit is used to pay for those operations.

Ø Overall amortized cost of
operations should be >= overall actual cost total credit should be
>= 0.

Ø The credit in the
amortized analysis is linked with a data structure.

 

·       
The accounting method itself includes two operations:

1.     Stack Operation

2.     Binary Operation

 

STACK
OPERATION: The stack operation consists of three operations:

1.    
Push

2.    
Pop

3.    
Multi-pops

 

§  To learn the counting
method of amortized analysis , here is the example:

Actual Costs:

Push    1,

Pop       1,

Multi pop   min (a, p)      
where a is argument given to the multi pop and p is size of a stack

Now, the assigned amortized cost

Push    2,

Pop      0,

Multi pop 0,

 

Now we can see that , the amortized cost of multi pop is 0
whereas the actual cost was a variable , so the overall amortized cost of three
operation is O(1). But the overall
cost of amortized operation is O(n).

But sometimes the amortized cost can be change
asymptotically.

 

 Binary Counter Increment:

The binary counter with the increment operation starts with
zero. The running time of increment operation is directly proportional to the
no.of bits flipped.

      Example:
Let us take an example of a Dollar bill to present each unit of cost.

               For amortized analysis , let charge an
amortized cost of 2 dollars to set it to a 1 dollar. If the bit is set , we
will take 1 dollar out 2 dollars to pay actual bit , then we place the left bit
as a credit. At the anyother time we can use that left 1 dollar , and our bit
will never reset to zero. We will just pay for the dollar reset bill. Thus the
number of 1’s in the counter can never be negative neither the amount of credit
can be negative. So for “n” increment operators the amount of total amortized cost
is O(n), in which actual cost is bound.