/**
* \fn int main()
*
* \brief Executes the mergesort() and the quicksort() algorithms on
* several arrays of varying size, and then computes the average
* execution time of each method on each array of the same size. The
* size of each array is always a power of 2, varying from 8 to
* 2^20. The average execution times are written out to the standard
* output.
*
* \return The status of the function termination.
*
* -------------------------------------------------------------------
*
* You should run this code with the following command-line:
*
* ./mainapp
*
* or
*
* ./mainapp > output filename
*
* -------------------------------------------------------------------
*/
int main()
{
/*
* Usage: ./mainapp [ > output filename ]
*/
/*
* Instantiate the mergesort and quicksort objects.
*/
MySort* ms_sorter = new MergeSort() ;
MySort* qs_sorter = new QuickSort() ;
/*
* Instantiate the array "shuffler".
*/
Shuffler shuffler ;
/*
* Set up the format for displaying the output numbers.
*/
cout << std::scientific << std::setprecision( 16 ) ;
/*
* Set up the execution params
*/
int begin_power = 3;
int end_power = 20;
int times_sorting = 5;
/*
* Run the method for arrays of size 2^i
*/
cerr << "Executing the sorting method on " << end_power - begin_power + 1
<< " distinctly-sized arrays (" << times_sorting << ") times for each)..."
<< endl ;
cerr << endl ;
cerr << "This may take some time... Get a coffee or play a game!"
<< endl ;
cerr << endl ;
int n = 2;
n <<= begin_power-1;
for ( int i = begin_power ; i <= end_power ; i++ ) {
cerr << endl ;
cerr << "-----------------------------------------------------"
<< endl ;
cerr << "Allocating memory for an array of size "
<< n << " (2^" << i << ")"
<< "..."
<< endl ;
/*
* Allocate memory for two arrays of n integers each.
*/
int* a = new int[ n ] ;
int* b = new int[ n ] ;
cerr << "Filling in the array with integers from 1 to "
<< n
<< "..."
<< endl ;
/*
* Fill out the array with the integers from 1 to n.
*/
for ( int i = 0 ; i < n ; i++ ) {
a[ i ] = i + 1 ;
}
/*
* Execute the method some times, each of which takes in a possibly
* distinct permutation of the array. This is not ideal, as the
* number of permutations of the arrays grows exponentially as we
* double the size of the array. However, if we try to be "fair"
* (say, by executing the method a number of times equal to 1% of
* the number of permutations), this application will take forever
* to run. So, just keep in mind that the average time is less
* representative as the size of the array grows (this is not
* ideal).
*/
cerr << "Shuffling and sorting the array " << times_sorting << " times..."
<< endl ;
double mstime = 0 ;
double qstime = 0 ;
for ( int j = 0 ; j < times_sorting ; j++ ) {
/*
* Shuffle the array (again). In principle, any permutation of
* the array is equally likely to be produced by the method
* shuffle().
*/
shuffler.shuffle( &a[ 0 ] , n ) ;
/*
* Make a copy of array "a".
*/
for ( int i = 0 ; i < n ; i++ ) {
b[ i ] = a[ i ] ;
}
/*
* Sort the array in non-decreasing order and record the time
* (in milliseconds) that the mergesort algorithm took to sort
* the array.
*/
clock_t start , end ;
start = clock() ;
ms_sorter->sort( a , n ) ;
end = clock() ;
/*
* Compute the cpu time of the execution.
*/
mstime += double( end - start ) ;
/*
* Check if the sorting method correctly sorted the array. If it
* did, then write out the size of the array and the execution
* time. Otherwise, write out an error message and abort the
* execution.
*/
for ( int j = 1 ; j < n ; j++ ) {
if ( a[ j ] < a[ j - 1 ] ) {
cerr << "Your implementation of the mergesort algorithm is incorrect!" << endl ;
return EXIT_FAILURE ;
}
}
/*
* Sort the array in non-decreasing order and record the time
* (in milliseconds) that the quick sort algorithm took to sort
* the array.
*/
start = clock() ;
qs_sorter->sort( b , n ) ;
end = clock() ;
/*
* Compute the cpu time of the execution.
*/
qstime += double( end - start ) ;
/*
* Check if the sorting method correctly sorted the array. If it
* did, then write out the size of the array and the execution
* time. Otherwise, write out an error message and abort the
* execution.
*/
for ( int j = 1 ; j < n ; j++ ) {
if ( b[ j ] < b[ j - 1 ] ) {
cerr << "Your implementation of the quicksort algorithm is incorrect!" << endl ;
return EXIT_FAILURE ;
}
}
cerr << "Done sorting for array with " << n << " elements "
<< "the " << j+1 << "th time"
<< endl ;
}
/*
* Write out array size and the average execution size.
*/
cout << n
<< '\t'
<< std::setw( 24 )
<< mstime / ( 100 * CLOCKS_PER_SEC )
<< '\t'
<< std::setw( 24 )
<< qstime / ( 100 * CLOCKS_PER_SEC )
<< endl ;
/*
* Double the size of the array.
*/
n <<= 1 ;
/*
* Release the memory allocated for the arrays "a" and "b".
*/
if ( a != 0 ) {
delete a ;
}
if ( b != 0 ) {
delete b ;
}
cerr << "-----------------------------------------------------"
<< endl ;
}
/*
* Release the memory allocated for the sorting method objects.
*/
if ( ms_sorter != 0 ) {
delete ms_sorter ;
}
if ( qs_sorter != 0 ) {
delete qs_sorter ;
}
cerr << endl << endl ;
return EXIT_SUCCESS ;
}
virtual void BeforeFirst(void) {
current = -1;
random->shuffle(nullptr);
}
/**
* \fn int main( int argc , char* argv[] )
*
* \brief Executes the insertion sort algorithm and the merge sort
* algorithm on several permutations of an array consisting of the
* integers 1 thru N, where N is a given positive integer. You can use
* this application to estimate the average execution time of both
* merge sort and insertion sort for "small" arrays. The idea is to
* estimate the largest value of N for which the average time taken by
* the insertion sort algorithm is smaller than the average time taken
* by the merge sort algorithm to sort some permutations of a given
* array of fixed size. Once you know N, you can change the code of
* the merge sort algorithm, so that it calls the insertion sort
* algorithm whenever the size of the subarray gets equal to or
* smaller than N.
*
* You should run this code with the following command-line:
*
* ./mainapp N
*
* \param argc The number of command line arguments.
* \param argv The command line arguments.
*
* \return The status of the function termination.
*/
int main( int argc, char* argv[] )
{
using std::cout ;
using std::cerr ;
using std::endl ;
/*
* Check the number of input parameters.
*/
if ( argc != 2 ) {
cerr << "Usage: ./mainapp N"
<< endl ;
return EXIT_FAILURE ;
}
/*
* Get the size of the array to be sorted.
*/
int n = atoi( argv[ 1 ] ) ;
assert( n > 0 ) ;
/*
* Instantiate the insertion sort and merge sort objects.
*/
MySort* is_sorter = new InsertionSort() ;
MySort* ms_sorter = new MergeSort() ;
/*
* Instantiate the array "shuffler".
*/
Shuffler shuffler ;
/*
* Set up the format for displaying the output numbers.
*/
cout << std::scientific << std::setprecision( 16 ) ;
/*
* Set up the execution params
*/
int times_sorting = 100;
/*
* Run the method for 100 permutations of an arrays of size n.
*/
cerr << "Executing the sorting method on " << n
<< "distinctly-sized arrays (" << times_sorting << ") times for each)..."
<< endl ;
cerr << "Allocating memory for an array of size "
<< n
<< "..."
<< endl ;
/*
* Allocate memory for two arrays of n integers each.
*/
int* a = new int[ n ] ;
int* b = new int[ n ] ;
cerr << "Filling in the array with integers from 1 to "
<< n
<< "..."
<< endl ;
/*
* Fill out the array with the integers from 1 to n.
*/
for ( int i = 0 ; i < n ; i++ ) {
a[ i ] = i + 1 ;
}
/*
* Execute the method 100 times, each of which takes in a possibly
* distinct permutation of the array.
*/
cerr << "Shuffling and sorting the array " << times_sorting
<< " times..." << endl ;
double istime = 0 ;
double mstime = 0 ;
for ( int j = 0 ; j < times_sorting ; j++ ) {
/*
* Shuffle the array (again). In principle, any permutation of the
* array is equally likely to be produced by the method shuffle().
*/
shuffler.shuffle( &a[ 0 ] , n ) ;
/*
* Make a copy of array "a".
*/
for ( int i = 0 ; i < n ; i++ ) {
b[ i ] = a[ i ] ;
}
/*
* Sort the array in non-decreasing order and record the time (in
* milliseconds) that the insertion sort algorithm took to sort
* the array.
*/
clock_t start , end ;
start = clock() ;
is_sorter->sort( a , n ) ;
end = clock() ;
/*
* Compute the cpu time of the execution.
*/
istime += double( end - start ) ;
/*
* Check if the sorting method correctly sorted the array. If it
* did, then write out the size of the array and the execution
* time. Otherwise, write out an error message and abort the
* execution.
*/
for ( int j = 1 ; j < n ; j++ ) {
if ( a[ j ] < a[ j - 1 ] ) {
cerr << "Your implementation of the insertion sort algorithm is incorrect!" << endl ;
return EXIT_FAILURE ;
}
}
/*
* Sort the array in non-decreasing order and record the time (in
* milliseconds) that the merge sort algorithm took to sort the
* array.
*/
start = clock() ;
ms_sorter->sort( b , n ) ;
end = clock() ;
/*
* Compute the cpu time of the execution.
*/
mstime += double( end - start ) ;
/*
* Check if the sorting method correctly sorted the array. If it
* did, then write out the size of the array and the execution
* time. Otherwise, write out an error message and abort the
* execution.
*/
for ( int j = 1 ; j < n ; j++ ) {
if ( b[ j ] < b[ j - 1 ] ) {
cerr << "Your implementation of the merge sort algorithm is incorrect!"
<< endl ;
return EXIT_FAILURE ;
}
}
cerr << "Done sorting for array with " << n << " elements "
<< "the " << j+1 << "th time"
<< endl ;
}
/*
* Write the average execution time of each method.
*/
cout << "INSERTION SORT: "
<< std::setw( 24 )
<< istime / ( 100 * CLOCKS_PER_SEC )
<< endl
<< " MERGE SORT: "
<< std::setw( 24 )
<< mstime / ( 100 * CLOCKS_PER_SEC )
<< endl ;
/*
* Release the memory allocated for the arrays.
*/
if ( a != 0 ) {
delete a ;
}
if ( b != 0 ) {
delete b ;
}
/*
* Release the memory allocated for the sorting method object.
*/
if ( is_sorter != 0 ) {
delete is_sorter ;
}
if ( ms_sorter != 0 ) {
delete ms_sorter ;
}
cerr << endl << endl ;
return EXIT_SUCCESS ;
}