opus/silk/sort.c

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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

/* Insertion sort (fast for already almost sorted arrays):   */
/* Best case:  O(n)   for an already sorted array            */
/* Worst case: O(n^2) for an inversely sorted array          */
/*                                                           */
/* Shell short:    https://en.wikipedia.org/wiki/Shell_sort  */

#include "SigProc_FIX.h"

void silk_insertion_sort_increasing(
    opus_int32           *a,             /* I/O   Unsorted / Sorted vector               */
    opus_int             *idx,           /* O     Index vector for the sorted elements   */
    const opus_int       L,              /* I     Vector length                          */
    const opus_int       K               /* I     Number of correctly sorted positions   */
)
{
    opus_int32    value;
    opus_int        i, j;

    /* Safety checks */
    silk_assert( K >  0 );
    silk_assert( L >  0 );
    silk_assert( L >= K );

    /* Write start indices in index vector */
    for( i = 0; i < K; i++ ) {
        idx[ i ] = i;
    }

    /* Sort vector elements by value, increasing order */
    for( i = 1; i < K; i++ ) {
        value = a[ i ];
        for( j = i - 1; ( j >= 0 ) && ( value < a[ j ] ); j-- ) {
            a[ j + 1 ]   = a[ j ];       /* Shift value */
            idx[ j + 1 ] = idx[ j ];     /* Shift index */
        }
        a[ j + 1 ]   = value;   /* Write value */
        idx[ j + 1 ] = i;       /* Write index */
    }

    /* If less than L values are asked for, check the remaining values, */
    /* but only spend CPU to ensure that the K first values are correct */
    for( i = K; i < L; i++ ) {
        value = a[ i ];
        if( value < a[ K - 1 ] ) {
            for( j = K - 2; ( j >= 0 ) && ( value < a[ j ] ); j-- ) {
                a[ j + 1 ]   = a[ j ];       /* Shift value */
                idx[ j + 1 ] = idx[ j ];     /* Shift index */
            }
            a[ j + 1 ]   = value;   /* Write value */
            idx[ j + 1 ] = i;       /* Write index */
        }
    }
}

#ifdef FIXED_POINT
/* This function is only used by the fixed-point build */
void silk_insertion_sort_decreasing_int16(
    opus_int16                  *a,                 /* I/O   Unsorted / Sorted vector                                   */
    opus_int                    *idx,               /* O     Index vector for the sorted elements                       */
    const opus_int              L,                  /* I     Vector length                                              */
    const opus_int              K                   /* I     Number of correctly sorted positions                       */
)
{
    opus_int i, j;
    opus_int value;

    /* Safety checks */
    silk_assert( K >  0 );
    silk_assert( L >  0 );
    silk_assert( L >= K );

    /* Write start indices in index vector */
    for( i = 0; i < K; i++ ) {
        idx[ i ] = i;
    }

    /* Sort vector elements by value, decreasing order */
    for( i = 1; i < K; i++ ) {
        value = a[ i ];
        for( j = i - 1; ( j >= 0 ) && ( value > a[ j ] ); j-- ) {
            a[ j + 1 ]   = a[ j ];     /* Shift value */
            idx[ j + 1 ] = idx[ j ];   /* Shift index */
        }
        a[ j + 1 ]   = value;   /* Write value */
        idx[ j + 1 ] = i;       /* Write index */
    }

    /* If less than L values are asked for, check the remaining values, */
    /* but only spend CPU to ensure that the K first values are correct */
    for( i = K; i < L; i++ ) {
        value = a[ i ];
        if( value > a[ K - 1 ] ) {
            for( j = K - 2; ( j >= 0 ) && ( value > a[ j ] ); j-- ) {
                a[ j + 1 ]   = a[ j ];     /* Shift value */
                idx[ j + 1 ] = idx[ j ];   /* Shift index */
            }
            a[ j + 1 ]   = value;   /* Write value */
            idx[ j + 1 ] = i;       /* Write index */
        }
    }
}
#endif

void silk_insertion_sort_increasing_all_values_int16(
     opus_int16                 *a,                 /* I/O   Unsorted / Sorted vector                                   */
     const opus_int             L                   /* I     Vector length                                              */
)
{
    opus_int    value;
    opus_int    i, j;

    /* Safety checks */
    silk_assert( L >  0 );

    /* Sort vector elements by value, increasing order */
    for( i = 1; i < L; i++ ) {
        value = a[ i ];
        for( j = i - 1; ( j >= 0 ) && ( value < a[ j ] ); j-- ) {
            a[ j + 1 ] = a[ j ]; /* Shift value */
        }
        a[ j + 1 ] = value; /* Write value */
    }
}