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#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include "SigProc_FLP.h"

silk_float silk_schur_FLP(                  /* O    returns residual energy                                     */

    silk_float          refl_coef[],        /* O    reflection coefficients (length order)                      */

    const silk_float    auto_corr[],        /* I    autocorrelation sequence (length order+1)                   */

    opus_int            order               /* I    order                                                       */

)

{

    opus_int   k, n;

    double C[ SILK_MAX_ORDER_LPC + 1 ][ 2 ];

    double Ctmp1, Ctmp2, rc_tmp;

    celt_assert( order >= 0 && order <= SILK_MAX_ORDER_LPC );

    /* Copy correlations */

    k = 0;

    do {

        C[ k ][ 0 ] = C[ k ][ 1 ] = auto_corr[ k ];

    } while( ++k <= order );

    for( k = 0; k < order; k++ ) {

        /* Get reflection coefficient */

        rc_tmp = -C[ k + 1 ][ 0 ] / silk_max_float( C[ 0 ][ 1 ], 1e-9f );

        /* Save the output */

        refl_coef[ k ] = (silk_float)rc_tmp;

        /* Update correlations */

        for( n = 0; n < order - k; n++ ) {

            Ctmp1 = C[ n + k + 1 ][ 0 ];

            Ctmp2 = C[ n ][ 1 ];

            C[ n + k + 1 ][ 0 ] = Ctmp1 + Ctmp2 * rc_tmp;

            C[ n ][ 1 ]         = Ctmp2 + Ctmp1 * rc_tmp;

        }

    }

    /* Return residual energy */

    return (silk_float)C[ 0 ][ 1 ];

}