Birla Institute of Technology and Science, Pilani Data
Structures and Algorithms
Lab: 3 (Tuesday, 25th Aug) Tuesday 18.08.09 QUICKSORT Max Marks:
16
Problem Statement:
1. Implement iterative version of the Quicksort algorithm. Use
Stack ADT to maintain the sub-list information. Input should be
generated randomly for a given size of array.
2. Measure the execution time in microseconds for the above
function for varying input sizes from 10 to 107. Use time.h library
functions for measuring execution time. Use of time functions is
demonstrated below. Compute NlogN for the different input sizes (N)
and estimate the constant of proportionality c so that all the
measured values are upper-bounded by cNlogN.
3. Measure the execution time of the recursive algorithm for
same sets of input data and find the ratio of improvement in
execution time for each input size.
4. Measure the maximum space utilized by both recursive and
iterative Quicksort
algorithms. For recursive algorithm maintain a counter for depth
of recursion to simulate maximum growth of machine stack. For
iterative algorithm, measure the maximum growth of the explicit
stack.
Measuring Execution Time:
#include
int main(int argc,char **argv)
{ ......
// Declaration of timeval variables which will capture the
system time
long time_start, time_end; struct timeval tv;
// Write all the initialization code here
// Time measurement begins here
gettimeofday(&tv,NULL); /*gets the current system time into
variable tv */ time_start = (tv.tv_sec *1e+6) + tv.tv_usec;
// calculating start time in seconds
// Write the code to be analyzed here
gettimeofday (&tv, NULL); time_end = (tv.tv_sec *1e+6) +
tv.tv_usec;
// calculating end time in seconds
// (time_end-time_start) gives the total execution time
return (0);
}
Given:
1. Implementation of recursive Quicksort algorithm.
2. ADT Stack
Deliverables:
1. Iterative Quicksort function in quicksortfunctions.c
2. Print comparative time analysis in following format in
main.c
Time and Space analysis of recursive Vs. iterative quicksort
Input size
n*logn Time (recursive)
Const (CR)
Time (Iterative)
Const(CI) Ratio of improvement
10 33.219 2.00 16.610 58.00 0.573 ..
5010 61575.879 1182.00 52.095 123593.00 0.498
(Sample output)
Input size
Space measured (recursive)
Space measured (iterative)
