Searching Analysis

Consider a finite collection of element. Finding whether element exsists in collection is known as Searching, Following is some of the comparision based Sorting Algorithms.

• Linear Search
• Binary Search

Before looking at the analysis part, we shall examine the Language in built methods to sorting

The in operator and list.index()

We have already seen the in operator in several contexts. Let’s see the working of in operator again

x = list(range(10))

x

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

6 in x

True

100 in x

False

x.index(6)

6

x.index(100)

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-0f87238c301b> in <module>()
----> 1 x.index(100)

ValueError: 100 is not in list

Standard import statement

from openanalysis.searching import SearchingAlgorithm,SearchVisualizer

SearchingAlgorithm is the base class providing the standards to implement sorting algorithms, SearchVisualizer visualizes and analyses the algorithm

SearchingAlgorithm class

Any searching algorithm, which has to be implemented, has to be derived from this class. Now we shall see data members and member functions of this class.

Data Members

• name - Name of the Searching Algorithm
• count - Holds the number of basic operations performed

Member Functions

• __init__(self, name): - Initializes algorithm with a name
• search(self, array, key): _ The base sorting function. Sets count to 0. array is 1D numpy array,key is the key of element to be found out

An example …. Binary Search

Now we shall implement the class BinarySearch

class BinarySearch(SearchingAlgorithm):                    # Inheriting
    def __init__(self):
        SearchingAlgorithm.__init__(self, "Binary Search") # Initailizing with name

    def search(self, arr, key):
        SearchingAlgorithm.search(self, arr, key)          # call base class search
        low, high = 0, arr.size - 1
        while low <= high:
            mid = int((low + high) / 2)
            self.count += 1                                # Increment for each basic operation performed
            if arr[mid] == key:
                return True
            elif arr[mid] < key:
                low = mid + 1
            else:
                high = mid - 1
        return False

SearchVisualizer class

This class provides the visualization and analysis methods. Let’s see its methods in detail

• __init__(self, searcher): Initializes visualizer with a Searching Algorithm.
  • searcher is a class, which is derived from SearchingAlgorithm
• analyze(self, maxpts=1000):
  • Plots the running time of searching algorithm by sorting for 3 cases
  • Key is the first element, Key is the last element, Key at random index
  • Analysis is done by inputting sorted integer arrays with size staring from 100, and varying upto maxpts in the steps of 100, and counting the number of basic operations
  • maxpts Upper bound on size of elements chosen for analysing efficiency

bin_visualizer = SearchVisualizer(BinarySearch)

bin_visualizer.analyze()

compare(algs)

algs is a list of classes derived from SearchingAlgorithm. It performs tests and plots the bar graph comapring the number of basic operations performed by each algorithm.

Example File

You can see more examples at Github