sorting - merge sort

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原创最新推荐文章于 2026-10-14 13:04:38 发布 565 阅读 AI 写同款· GEO 优化 ›

高级数据库二十：并行JOIN算法（Sorting） Parallel Join Algorithms (Sorting) 背景关于Join的其他背景可以查看上一篇讲Hash Join的文章。 SINGLE INSTRUCTION, MULTIPLE DATA (SIMD) 有一系列的CPU指令允许处理器同时在多个数据点上执行相同的操作。目前的AMD和Intel CPU均具有ISA和微体系结构，支持SIMD操作。优点：阅读详情

#include "stdio.h"
#include "string.h"

#define MAX_LIST 50


typedef struct _SqList {
    int data[MAX_LIST];
    int length;
}SqList;

enum MERGE_SORT_METHOD { RECURSE, ITERATE };

void Merge( int src[], int dst[], int start, int middle, int end)
{
    int j, k;
    for( k = start, j = middle + 1; start <= middle && j <= end; k++   )
    {
        if( src[start] < src[j] )
            dst[k] = src[start++];
        else
            dst[k] = src[j++];      
    }

    while( start <= middle ) dst[k++] = src[start++];
    while( j <= end ) dst[k++] = src[j++];      
}

void MSort( int src[], int dst[], int start, int end )
{
    if( start == end )
        dst[start] = src[start];
    else{
        int middle = (start + end)/2;
        int buf[MAX_LIST];
        MSort(src, buf, start, middle);
        MSort(src, buf, middle+1, end);
        Merge(buf, dst, start, middle, end );
    }
}
void MergeSortRecursive( SqList* L )
{
     MSort( L->data, L->data, 0, L->length-1 );
}

void MergePiecewise( int src[], int dst[], int piece, int count )
{
    int i = 0;
    while( i < count - 2*piece + 1)
    {
        Merge( src, dst, i, i+piece-1, i+2*piece-1);
        i += 2*piece;
    }   
    if( i < count -  piece + 1 )
        Merge( src, dst, i, i + piece - 1, count-1);
    else
        while( i < count )
            dst[i] = src[i++];
}
void MergeSortIterative( SqList* L )
{
    int buf[MAX_LIST];

    int block = 1;
    while( block < L->length )
    {
        MergePiecewise( L->data, buf, block, L->length  );
        block *= 2;
        MergePiecewise( buf, L->data, block, L->length );
        block *= 2;
    }
}

void MergeSort( SqList* L, MERGE_SORT_METHOD ms )
{
    if( ms == RECURSE )
        MergeSortRecursive( L );
    else
        MergeSortIterative( L );
}

int main()
{
    SqList d;
    int intarr[] = {1,10,23,48,65,31,-21,9,88,100};
    printf("array length is %d\n", sizeof(intarr));
    memcpy( d.data, intarr, sizeof(intarr));
    d.length = sizeof(intarr)/sizeof(int);  
    int index = 0;
    for( ; index < d.length; index++ )
        printf(" %d", d.data[index] );
    printf("\nMerge sort...\n");
    MergeSort( &d, RECURSE );
    for( index = 0; index < d.length; index++ )
        printf(" %d", d.data[index] );
    printf("\n");
    return 0;
}