source: src/tests/concurrent/examples/quickSort.c @ bc03be3

//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// quickSort.c -- In-place concurrent quick-sort: threads are created to partition to a specific depth, then sequential
//              recursive-calls are use to sort each partition.
//
// Author           : Peter A. Buhr
// Created On       : Wed Dec  6 12:15:52 2017
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Jan 30 15:58:58 2018
// Update Count     : 162
//

#include <fstream>
#include <stdlib>
#include <kernel>
#include <thread>
#include <string.h>                                                                             // strcmp

thread Quicksort {
        int * values;                                                                           // communication variables
        int low, high, depth;
};

void ?{}( Quicksort & qs, int values[], int size, int depth ) {
        qs.values = values;  qs.low = 0;  qs.high = size;  qs.depth = depth;
} // Quicksort

void main( Quicksort & qs ) {                                                   // thread starts here
        // nested routines: information hiding

        void ?{}( Quicksort & qs, int values[], int low, int high, int depth ) {
                qs.values = values;  qs.low = low;  qs.high = high;  qs.depth = depth;
        } // Quicksort

        void sort( int values[], int low, int high, int depth ) {
                int left, right;                                                                // index to left/right-hand side of the values
                int pivot;                                                                              // pivot value of values
                int swap;                                                                               // temporary

                //verify();                                                                             // check for stack overflow due to recursion

                // partition while 2 or more elements in the array
                if ( low < high ) {
                        pivot = values[low + ( high - low ) / 2];
                        left  = low;
                        right = high;

                        // partition: move values less < pivot before the pivot and values > pivot after the pivot
                        do {
                                while ( values[left] < pivot ) left += 1; // changed values[left] < pivot
                                while ( pivot < values[right] ) right -= 1;
                                if ( left <= right ) {
                                        swap = values[left];                            // interchange values
                                        values[left]  = values[right];
                                        values[right] = swap;
                                        left += 1;
                                        right -= 1;
                                } // if
                        } while ( left <= right );

                        // restrict number of tasks to slightly greater than number of processors
                        if ( depth > 0 ) {
                                depth -= 1;
                                Quicksort rqs = { values, low, right, depth }; // concurrently sort upper half
                                //Quicksort lqs( values, left, high, depth ); // concurrently sort lower half
                                sort( values, left, high, depth );              // concurrently sort lower half
                        } else {
                                sort( values, low, right, 0 );                  // sequentially sort lower half
                                sort( values, left, high, 0 );                  // sequentially sort upper half
                        } // if
                } // if
        } // sort

        with( qs ) {
                sort( values, low, high, depth );
        } // with
} // main


bool convert( int & val, const char * nptr ) {                  // convert C string to integer
        char * eptr;
        int temp = strto( nptr, &eptr, 10 );                            // do not change val on false
        // true => entire string valid with no extra characters
        return *nptr != '\0' && *eptr == '\0' ? val = temp, true : false;
} // convert

void usage( char * argv[] ) {
        sout | "Usage:" | argv[0] | "( -s unsorted-file [ sorted-file ] | -t size (>= 0) [ depth (>= 0) ] )" | endl;
        exit( EXIT_FAILURE );                                                           // TERMINATE!
} // usage


int main( int argc, char * argv[] ) {
        ifstream & unsortedfile = sin;
        ofstream & sortedfile = sout;                                           // default value
        int depth = 0, size;

        if ( argc != 1 ) {                                                                      // do not use defaults
                if ( argc < 2 || argc > 4 ) usage( argv );              // wrong number of options
                if ( strcmp( argv[1], "-t" ) == 0 ) {                   // timing ?
                        &unsortedfile = (ifstream *)0;                          // no input
                        choose ( argc ) {
                          case 4:
                                if ( ! convert( depth, argv[3] ) || depth < 0 ) usage( argv );
                                fallthrough;
                          case 3:
                                if ( ! convert( size, argv[2] ) || size < 0 ) usage( argv );
                        } // choose
                } else {                                                                                // sort file
                        choose ( argc ) {
                          case 3:
                                &sortedfile = new( (const char *)argv[2] ); // open the output file
                                if ( fail( sortedfile ) ) {
                                        serr | "Error! Could not open sorted output file \"" | argv[2] | "\"" | endl;
                                        usage( argv );
                                } // if
                                fallthrough;
                          case 2:
                                &unsortedfile = new( (const char *)argv[1] ); // open the input file
                                if ( fail( unsortedfile ) ) {
                                        serr | "Error! Could not open unsorted input file \"" | argv[1] | "\"" | endl;
                                        usage( argv );
                                } // if
                        } // choose
                } // if
        } // if

        enum { ValuesPerLine = 22 };                                            // number of values printed per line

        if ( &unsortedfile ) {                                                          // generate output ?
                for ( ;; ) {
                        unsortedfile | size;                                            // read number of elements in the list
                  if ( eof( unsortedfile ) ) break;
                        int * values = alloc( size );                           // values to be sorted, too large to put on stack
                        for ( int counter = 0; counter < size; counter += 1 ) { // read unsorted numbers
                                unsortedfile | values[counter];
                                if ( counter != 0 && counter % ValuesPerLine == 0 ) sortedfile | endl | "  ";
                                sortedfile | values[counter];
                                if ( counter < size - 1 && (counter + 1) % ValuesPerLine != 0 ) sortedfile | ' ';
                        } // for
                        sortedfile | endl;
                        if ( size > 0 ) {                                                       // values to sort ?
                                Quicksort QS = { values, size - 1, 0 }; // sort values
                        } // wait until sort tasks terminate
                        for ( int counter = 0; counter < size; counter += 1 ) { // print sorted list
                                if ( counter != 0 && counter % ValuesPerLine == 0 ) sortedfile | endl | "  ";
                                sortedfile | values[counter];
                                if ( counter < size - 1 && (counter + 1) % ValuesPerLine != 0 ) sortedfile | ' ';
                        } // for
                        sortedfile | endl | endl;

                        delete( values );
                } // for
                if ( &unsortedfile != &sin ) delete( &unsortedfile ); // close input/output files
                if ( &sortedfile != &sout ) delete( &sortedfile );
        } else {
                processor processors[ (1 << depth) - 1 ] __attribute__(( unused )); // create 2^depth-1 kernel threads

                int * values = alloc( size );                           // values to be sorted, too large to put on stack
                for ( int counter = 0; counter < size; counter += 1 ) { // generate unsorted numbers
                        values[counter] = size - counter;                       // descending values
                } // for
                {
                        Quicksort QS = { values, size - 1, depth }; // sort values
                } // wait until sort tasks terminate

                // for ( int counter = 0; counter < size - 1; counter += 1 ) { // check sorting
                //      if ( values[counter] > values[counter + 1] ) abort();
                // } // for

                delete( values );
        } // if
} // main

// Local Variables: //
// tab-width: 4 //
// compile-command: "cfa quickSort.c" //
// End: //