FLA_Bidiag_UT_form_U_ext.c File Reference

(r)

Functions
FLA_Error	FLA_Bidiag_UT_form_U_ext (FLA_Uplo uplo, FLA_Obj A, FLA_Obj T, FLA_Trans transu, FLA_Obj U)

Function Documentation

FLA_Bidiag_UT_form_U_ext()

FLA_Error FLA_Bidiag_UT_form_U_ext	(	FLA_Uplo	uplo,
		FLA_Obj	A,
		FLA_Obj	T,
		FLA_Trans	transu,
		FLA_Obj	U )

{
    //if ( FLA_Check_error_level() >= FLA_MIN_ERROR_CHECKING )
    //  FLA_Bidiag_UT_form_U_ext_check( uplo, A, T, transu, U );
 
    if ( transu == FLA_NO_TRANSPOSE ||
         transu == FLA_CONJ_NO_TRANSPOSE )
    {
 
        if ( uplo == FLA_UPPER_TRIANGULAR )
        {
            FLA_QR_UT_form_Q( A, T, U );
        }
        else // if ( uplo == FLA_LOWER_TRIANGULAR )
        {
            FLA_Obj ATL, ATR,
                    ABL, ABR;
 
            FLA_Obj UTL, UTR,
                    UBL, UBR;
 
            FLA_Obj TL,  TR;
 
            dim_t   b = ( FLA_Obj_length( A ) - 1 );
 
            FLA_Part_1x2( T,    &TL,  &TR,     1, FLA_RIGHT );
            FLA_Part_2x2( U,    &UTL, &UTR,
                                &UBL, &UBR,    1, 1, FLA_TL );
 
            if ( FLA_Obj_is( A, U ) == FALSE )
            {
                FLA_Set( FLA_ONE,  UTL ); FLA_Set( FLA_ZERO, UTR );
                FLA_Set( FLA_ZERO, UBL );
 
                FLA_Part_2x2( A,    &ATL, &ATR,
                                    &ABL, &ABR,    1, b, FLA_TL );
 
                FLA_QR_UT_form_Q( ABL, TL, UBR );
            }
            else
            {
                FLA_Obj p, pt, pb;
                FLA_Part_2x2( A,    &ATL, &ATR,
                                    &ABL, &ABR,    1, b+1, FLA_TL );
 
                FLA_Obj_create( FLA_INT, b+1,1, 0, 0, &p );
                FLA_Part_2x1( p,    &pt,
                                    &pb, 1, FLA_BOTTOM );
                FLA_Set( FLA_ONE, pt );
                FLA_Set( FLA_ZERO, pb );
                FLA_Apply_pivots ( FLA_RIGHT, FLA_NO_TRANSPOSE, p, ABL );
                FLA_Obj_free(&p );
 
                FLA_Set( FLA_ONE,  UTL );
                FLA_Set( FLA_ZERO, UBL );
                FLA_Set( FLA_ZERO, UTR );
 
                FLA_Part_1x2( ABL,  &ABL,
                                    &ABR, 1, FLA_LEFT );
 
                FLA_QR_UT_form_Q( ABR, TL, UBR );
            }
        }
    }
    else
    {
        FLA_Uplo uplo_flip = ( uplo == FLA_UPPER_TRIANGULAR ?
                               FLA_LOWER_TRIANGULAR : FLA_UPPER_TRIANGULAR );
 
        FLA_Obj_flip_base( &A );
        FLA_Obj_flip_view( &A );
 
        // A and U should have different base objects
        FLA_Bidiag_UT_form_V_ext( uplo_flip,  A, T,
                                  FLA_CONJ_TRANSPOSE, U );
 
        FLA_Obj_flip_base( &A );
 
        // As we use QR and LQ for constructing U and V, 
        // conjugation naturally fits there. 
        // Never apply conjugation separately here even if flipping trick is applied.
        //FLA_Conjugate( U );
    }
 
    return FLA_SUCCESS;
}

References FLA_Apply_pivots(), FLA_Bidiag_UT_form_V_ext(), FLA_Obj_create(), FLA_Obj_flip_base(), FLA_Obj_flip_view(), FLA_Obj_free(), FLA_Obj_is(), FLA_Obj_length(), FLA_ONE, FLA_Part_1x2(), FLA_Part_2x1(), FLA_Part_2x2(), FLA_QR_UT_form_Q(), FLA_Set(), and FLA_ZERO.

Referenced by FLA_Bidiag_UT_form_U(), FLA_Bidiag_UT_form_V_ext(), and FLA_Svd_ext_u_unb_var1().