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#include "SKP_Silk_main_FLP.h"

#define MAX_ITERATIONS_RESIDUAL_NRG         10
#define REGULARIZATION_FACTOR               1e-8f

/* Residual energy: nrg = wxx - 2 * wXx * c + c' * wXX * c */
SKP_float SKP_Silk_residual_energy_covar_FLP(           /* O    Weighted residual energy                */
    const SKP_float                 *c,                 /* I    Filter coefficients                     */
          SKP_float                 *wXX,               /* I/O  Weighted correlation matrix, reg. out   */
    const SKP_float                 *wXx,               /* I    Weighted correlation vector             */
    const SKP_float                 wxx,                /* I    Weighted correlation value              */
    const SKP_int                   D                   /* I    Dimension                               */
)
{
    SKP_int   i, j, k;
    SKP_float tmp, nrg, regularization;

    /* Safety checks */
    SKP_assert( D >= 0 );

    regularization = REGULARIZATION_FACTOR * ( wXX[ 0 ] + wXX[ D * D - 1 ] );
    for( k = 0; k < MAX_ITERATIONS_RESIDUAL_NRG; k++ ) {
        nrg = wxx;

        tmp = 0.0f;
        for( i = 0; i < D; i++ ) {
            tmp += wXx[ i ] * c[ i ];
        }
        nrg -= 2.0f * tmp;

        /* compute c' * wXX * c, assuming wXX is symmetric */
        for( i = 0; i < D; i++ ) {
            tmp = 0.0f;
            for( j = i + 1; j < D; j++ ) {
                tmp += matrix_c_ptr( wXX, i, j, D ) * c[ j ];
            }
            nrg += c[ i ] * ( 2.0f * tmp + matrix_c_ptr( wXX, i, i, D ) * c[ i ] );
        }
        if( nrg > 0 ) {
            break;
        } else {
            /* Add white noise */
            for( i = 0; i < D; i++ ) {
                matrix_c_ptr( wXX, i, i, D ) +=  regularization;
            }
            /* Increase noise for next run */
            regularization *= 2.0f;
        }
    }
    if( k == MAX_ITERATIONS_RESIDUAL_NRG ) {
        SKP_assert( nrg == 0 );
        nrg = 1.0f;
    }

    return nrg;
}

/* Calculates residual energies of input subframes where all subframes have LPC_order   */
/* of preceeding samples                                                                */
void SKP_Silk_residual_energy_FLP(  
          SKP_float nrgs[],                     /* O    Residual energy per subframe    */
    const SKP_float x[],                        /* I    Input signal                    */
          SKP_float a[ 2 ][ MAX_LPC_ORDER ],    /* I    AR coefs for each frame half    */
    const SKP_float gains[],                    /* I    Quantization gains              */
    const SKP_int   subfr_length,               /* I    Subframe length                 */
    const SKP_int   LPC_order                   /* I    LPC order                       */
)
{
    SKP_int     shift;
    SKP_float   *LPC_res_ptr, LPC_res[ ( MAX_FRAME_LENGTH + NB_SUBFR * MAX_LPC_ORDER ) / 2 ];

    LPC_res_ptr = LPC_res + LPC_order;
    shift = LPC_order + subfr_length;

    /* Filter input to create the LPC residual for each frame half, and measure subframe energies */
    SKP_Silk_LPC_analysis_filter_FLP( LPC_res, a[ 0 ], x + 0 * shift, 2 * shift, LPC_order );
    nrgs[ 0 ] = ( SKP_float )( gains[ 0 ] * gains[ 0 ] * SKP_Silk_energy_FLP( LPC_res_ptr + 0 * shift, subfr_length ) );
    nrgs[ 1 ] = ( SKP_float )( gains[ 1 ] * gains[ 1 ] * SKP_Silk_energy_FLP( LPC_res_ptr + 1 * shift, subfr_length ) );

    SKP_Silk_LPC_analysis_filter_FLP( LPC_res, a[ 1 ], x + 2 * shift, 2 * shift, LPC_order );
    nrgs[ 2 ] = ( SKP_float )( gains[ 2 ] * gains[ 2 ] * SKP_Silk_energy_FLP( LPC_res_ptr + 0 * shift, subfr_length ) );
    nrgs[ 3 ] = ( SKP_float )( gains[ 3 ] * gains[ 3 ] * SKP_Silk_energy_FLP( LPC_res_ptr + 1 * shift, subfr_length ) );
}
