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test_parallel_scan.cpp

/*
    Copyright 2005-2007 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks is distributed in the hope that it will be
    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#include "tbb/parallel_scan.h"
#include "tbb/blocked_range.h"
#include "harness_assert.h"

typedef tbb::blocked_range<long> Range;

static volatile bool ScanIsRunning = false;

//! Sum of 0..i with wrap around on overflow.
inline int TriangularSum( int i ) {
    return i&1 ? ((i>>1)+1)*i : (i>>1)*(i+1); 
}

//! Verify that sum is sum of integers in closed interval [start_index..finish_index].
/** line should be the source line of the caller */
static void VerifySum( long start_index, long finish_index, int sum, int line );

const int MAXN = 2000;

enum AddendFlag {
    UNUSED=0,
    USED_NONFINAL=1,
    USED_FINAL=2
};

//! Array recording how each addend was used. 
/** 'unsigned char' instead of AddendFlag for sake of compactness. */
static unsigned char AddendHistory[MAXN];

//! Set to 1 for debugging output 
#define PRINT_DEBUG 0

#include "tbb/atomic.h"
#if PRINT_DEBUG
#include <stdio.h>
tbb::atomic<long> NextBodyId;
#endif /* PRINT_DEBUG */

struct BodyId {
#if PRINT_DEBUG
    const int id;
    BodyId() : id(NextBodyId++) {}
#endif /* PRINT_DEBUG */
};

tbb::atomic<long> NumberOfLiveAccumulator;

static void Snooze( bool scan_should_be_running ) {
    ASSERT( ScanIsRunning==scan_should_be_running, NULL );
}

template<typename T>
class Accumulator: BodyId {
    T my_total;
    const T* my_array;
    T* my_sum;
    Range my_range;
    //! Equals this while object is fully constructed, NULL otherwise.
    /** Used to detect premature destruction and accidental bitwise copy. */
    Accumulator* self;
    Accumulator( const T array[], T sum[] ) :
        my_total(), my_array(array), my_sum(sum), my_range(-1,-1,1)
    {
        ++NumberOfLiveAccumulator;
        // Set self as last action of constructor, to indicate that object is fully constructed.
        self = this;
    }
    friend void TestAccumulator( int mode, int nthread );
public:
#if PRINT_DEBUG
    void print() const {
        printf("%d [%ld..%ld)\n", id,my_range.begin(),my_range.end() );
    }
#endif /* PRINT_DEBUG */
    ~Accumulator() {
#if PRINT_DEBUG
        printf("%d [%ld..%ld) destroyed\n",id,my_range.begin(),my_range.end() ); 
#endif /* PRINT_DEBUG */
        // Clear self as first action of destructor, to indicate that object is not fully constructed.
        self = 0;
        --NumberOfLiveAccumulator;
    }
    Accumulator( Accumulator& a, tbb::split ) : 
        my_total(0), my_array(a.my_array), my_sum(a.my_sum), my_range(-1,-1,1)  
    {
        ++NumberOfLiveAccumulator;
#if PRINT_DEBUG
        printf("%d forked from %d\n",id,a.id);
#endif /* PRINT_DEBUG */
        Snooze(true);
        // Set self as last action of constructor, to indicate that object is fully constructed.
        self = this;
    }
    template<typename Tag> 
    void operator()( const Range& r, Tag tag ) {
        Snooze(true);
#if PRINT_DEBUG
        if( my_range.empty() )
            printf("%d computing %s [%ld..%ld)\n",id,tag.is_final_scan()?"final":"lookahead",r.begin(),r.end() );
        else
            printf("%d computing %s [%ld..%ld) [%ld..%ld)\n",id,tag.is_final_scan()?"final":"lookahead",my_range.begin(),my_range.end(),r.begin(),r.end());
#endif /* PRINT_DEBUG */
        ASSERT( !tag.is_final_scan() || my_range.begin()==0 && my_range.end()==r.begin() || my_range.empty() && r.begin()==0, NULL );
        for( long i=r.begin(); i<r.end(); ++i ) {
            my_total += my_array[i];
            if( tag.is_final_scan() ) {
                ASSERT( AddendHistory[i]<USED_FINAL, "addend used 'finally' twice?" );
                AddendHistory[i] |= USED_FINAL;
                my_sum[i] = my_total;
                VerifySum( 0L, i, int(my_sum[i]), __LINE__ );
            } else {
                ASSERT( AddendHistory[i]==UNUSED, "addend used too many times" );
                AddendHistory[i] |= USED_NONFINAL;
            }   
        }
        if( my_range.empty() )
            my_range = r;
        else
            my_range = Range(my_range.begin(), r.end(), 1 );
        Snooze(true);
        ASSERT( self==this, "this Accumulator corrupted or prematurely destroyed" );
    }
    void reverse_join( const Accumulator& left ) {
#if PRINT_DEBUG
        printf("reverse join %d [%ld..%ld) %d [%ld..%ld)\n",
               left.id,left.my_range.begin(),left.my_range.end(),
               id,my_range.begin(),my_range.end());
#endif /* PRINT_DEBUG */
        Snooze(true);
        ASSERT( ScanIsRunning, NULL );     
        ASSERT( left.my_range.end()==my_range.begin(), NULL );
        my_total += left.my_total;
        my_range = Range( left.my_range.begin(), my_range.end(), 1 );
        ASSERT( ScanIsRunning, NULL );     
        Snooze(true);
        ASSERT( ScanIsRunning, NULL );     
        ASSERT( self==this, NULL );
        ASSERT( left.self==&left, NULL );
    }
    void assign( const Accumulator& other ) {
        my_total = other.my_total;
        my_range = other.my_range;
        ASSERT( self==this, NULL );
        ASSERT( other.self==&other, "other Accumulator corrupted or prematurely destroyed" );
    }
};

#include "tbb/tick_count.h"
#include "harness.h"

static void VerifySum( long start_index, long finish_index, int sum, int line ) {
    int expected = TriangularSum( finish_index ) - TriangularSum( start_index );
    if( expected!=sum ) {
        printf("line %d: sum[%ld..%ld] should be = %d, but was computed as %d\n", line, start_index, finish_index, expected, sum );
        abort();
    }
}

void TestAccumulator( int mode, int nthread ) {
    typedef int T;
    T* addend = new T[MAXN];
    T* sum = new T[MAXN];
    for( long n=0; n<=MAXN; ++n ) {
        for( long i=0; i<MAXN; ++i ) {
            addend[i] = -1;
            sum[i] = -2;
            AddendHistory[i] = UNUSED;
        }
        for( long i=0; i<n; ++i )
            addend[i] = i;
        Accumulator<T> acc( addend, sum );
        tbb::tick_count t0 = tbb::tick_count::now();
#if PRINT_DEBUG
        printf("--------- mode=%d range=[0..%ld)\n",mode,n);
#endif /* PRINT_DEBUG */
        ScanIsRunning = true;

        switch (mode) {
            case 0:
                tbb::parallel_scan( Range( 0, n, 1 ), acc );
            break;
            case 1:
                tbb::parallel_scan( Range( 0, n, 1 ), acc, tbb::simple_partitioner() );
            break;
            case 2:
                tbb::parallel_scan( Range( 0, n, 1 ), acc, tbb::auto_partitioner() );
            break;
        }

        ScanIsRunning = false;
#if PRINT_DEBUG
        printf("=========\n");
#endif /* PRINT_DEBUG */
        Snooze(false);
        tbb::tick_count t1 = tbb::tick_count::now();
        long used_once_count = 0;
        for( long i=0; i<n; ++i ) 
            if( !(AddendHistory[i]&USED_FINAL) ) {
                printf("failed to use addend[%ld] %s\n",i,AddendHistory[i]&USED_NONFINAL?"(but used nonfinal)":"");
            }
        for( long i=0; i<n; ++i ) {
            VerifySum( 0, i, sum[i], __LINE__ );
            used_once_count += AddendHistory[i]==USED_FINAL;
        }
        if( n )
            ASSERT( acc.my_total==sum[n-1], NULL );
        else
            ASSERT( acc.my_total==0, NULL );
        if( Verbose ) 
            printf("time [n=%ld] = %g\tused_once%% = %g\tnthread=%d\n",n,(t1-t0).seconds(), n==0 ? 0 : 100.0*used_once_count/n,nthread);
    }
    delete[] addend;
    delete[] sum;
}

static void TestScanTags() {
    ASSERT( tbb::pre_scan_tag::is_final_scan()==false, NULL );
    ASSERT( tbb::final_scan_tag::is_final_scan()==true, NULL );
}

#include "tbb/task_scheduler_init.h"
#include "harness_cpu.h"

int main(int argc, char* argv[]) {
    ParseCommandLine(argc,argv);
    TestScanTags();
    for( int p=MinThread; p<=MaxThread; ++p ) {
        for (int mode = 0; mode < 3; mode++) {
            tbb::task_scheduler_init init(p);
            NumberOfLiveAccumulator = 0;
            TestAccumulator(mode, p);

            // Test that all workers sleep when no work
            TestCPUUserTime(p-1);

            // Checking has to be done late, because when parallel_scan makes copies of
            // the user's "Body", the copies might be destroyed slightly after parallel_scan 
            // returns.
            ASSERT( NumberOfLiveAccumulator==0, NULL );
        }
    }
    printf("done\n");
    return 0;
}

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