FLA_Tevd_find_submatrix.c File Reference

(r)

Functions
FLA_Error	FLA_Tevd_find_submatrix_ops (int m_A, int ij_begin, float *buff_d, int inc_d, float *buff_e, int inc_e, int *ijTL, int *ijBR)
FLA_Error	FLA_Tevd_find_submatrix_opd (int m_A, int ij_begin, double *buff_d, int inc_d, double *buff_e, int inc_e, int *ijTL, int *ijBR)

Function Documentation

FLA_Tevd_find_submatrix_opd()

FLA_Error FLA_Tevd_find_submatrix_opd	(	int	m_A,
		int	ij_begin,
		double *	buff_d,
		int	inc_d,
		double *	buff_e,
		int	inc_e,
		int *	ijTL,
		int *	ijBR )

{
    double rzero = bl1_d0();
    double eps;
    int    ij_tl;
    int    ij_br;
 
    // Initialize some numerical constants.
    eps = FLA_Mach_params_opd( FLA_MACH_EPS );
 
    // Search for the first non-zero subdiagonal element starting at
    // the index specified by ij_begin.
    for ( ij_tl = ij_begin; ij_tl < m_A - 1; ++ij_tl )
    {
        double* d1     = buff_d + (ij_tl  )*inc_d;
        double* d2     = buff_d + (ij_tl+1)*inc_d;
        double* e1     = buff_e + (ij_tl  )*inc_e;
        double  abs_e1 = fabs( *e1 );
 
        // If we encounter a non-zero subdiagonal element that is close
        // enough to zero, set it to zero.
        if ( abs_e1 != rzero )
        {
            if ( abs_e1 <= eps * sqrt( fabs( *d1 ) ) *
                                 sqrt( fabs( *d2 ) ) )
            {
#ifdef PRINTF
printf( "FLA_Tevd_find_submatrix_opd: nudging non-zero subdiagonal element (e1) to zero.\n" );
printf( "                             d[%3d]        = %22.19e\n", ij_tl, *d1 );
printf( "                             e[%3d] d[%3d] = %22.19e %22.19e\n", ij_tl, ij_tl+1, *e1, *d2 );
#endif
                *e1 = rzero;
            }
        }
 
        // If we find a non-zero element, record it and break out of this
        // loop.
        if ( *e1 != rzero )
        {
#ifdef PRINTF
printf( "FLA_Tevd_find_submatrix_opd: found non-zero subdiagonal element\n" );
printf( "                             e[%3d] = %22.19e\n", ij_tl, *e1 );
#endif
            *ijTL = ij_tl;
            break;
        }
    }
 
    // If ij_tl was incremented all the way up to m_A - 1, then we didn't
    // find any non-zeros.
    if ( ij_tl == m_A - 1 )
    {
#ifdef PRINTF
printf( "FLA_Tevd_find_submatrix_opd: no submatrices found.\n" );
#endif
        return FLA_FAILURE;
    }
 
    // If we've gotten this far, then a non-zero subdiagonal element was
    // found. Now we must walk the remaining portion of the subdiagonal
    // to find the first zero element, or if one is not found, we simply
    // use the last element of the subdiagonal.
    for ( ij_br = ij_tl; ij_br < m_A - 1; ++ij_br )
    {
        double* d1     = buff_d + (ij_br  )*inc_d;
        double* d2     = buff_d + (ij_br+1)*inc_d;
        double* e1     = buff_e + (ij_br  )*inc_e;
        double  abs_e1 = fabs( *e1 );
 
        // If we encounter a non-zero subdiagonal element that is close
        // enough to zero, set it to zero.
        if ( abs_e1 != rzero )
        {
            if ( abs_e1 <= eps * sqrt( fabs( *d1 ) ) *
                                 sqrt( fabs( *d2 ) ) )
            {
#ifdef PRINTF
printf( "FLA_Tevd_find_submatrix_opd: nudging non-zero subdiagonal element (e1) to zero.\n" );
printf( "                             d[%3d]        = %22.19e\n", ij_br, *d1 );
printf( "                             e[%3d] d[%3d] = %22.19e %22.19e\n", ij_br, ij_br+1, *e1, *d2 );
#endif
                *e1 = rzero;
            }
        }
 
        // If we find a zero element, record it and break out of this
        // loop.
        if ( *e1 == rzero )
        {
#ifdef PRINTF
printf( "FLA_Tevd_find_submatrix_opd: found zero subdiagonal element\n" );
printf( "                             e[%3d] = %22.19e\n", ij_br, *e1 );
#endif
            break;
        }
    }
 
    // If a zero element was found, then ij_br should hold the index of
    // that element. If a zero element was not found, then ij_br should
    // hold m_A - 1. Either way, we save the value and return success.
    *ijBR = ij_br;
 
    return FLA_SUCCESS;
}

References bl1_d0(), and FLA_Mach_params_opd().

Referenced by FLA_Tevd_n_opz_var1(), FLA_Tevd_v_opd_var1(), FLA_Tevd_v_opd_var2(), FLA_Tevd_v_opz_var1(), and FLA_Tevd_v_opz_var2().

FLA_Tevd_find_submatrix_ops()

FLA_Error FLA_Tevd_find_submatrix_ops	(	int	m_A,
		int	ij_begin,
		float *	buff_d,
		int	inc_d,
		float *	buff_e,
		int	inc_e,
		int *	ijTL,
		int *	ijBR )

{
    FLA_Check_error_code( FLA_NOT_YET_IMPLEMENTED );
 
    return FLA_SUCCESS;
}