FLA_Svd_compute_scaling.c File Reference

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Functions
FLA_Error	FLA_Svd_compute_scaling (FLA_Obj A, FLA_Obj sigma)

Function Documentation

FLA_Svd_compute_scaling()

FLA_Error FLA_Svd_compute_scaling	(	FLA_Obj	A,
		FLA_Obj	sigma )

{
    FLA_Datatype dt_real;
    FLA_Obj      norm;
    FLA_Obj      safmin;
    FLA_Obj      prec;
    FLA_Obj      rmin;
    FLA_Obj      rmax;
 
    if ( FLA_Check_error_level() >= FLA_MIN_ERROR_CHECKING )
        FLA_Svd_compute_scaling_check( A, sigma );
 
    dt_real = FLA_Obj_datatype_proj_to_real( A );
 
    FLA_Obj_create( dt_real, 1, 1, 0, 0, &norm );
    FLA_Obj_create( dt_real, 1, 1, 0, 0, &prec );
    FLA_Obj_create( dt_real, 1, 1, 0, 0, &safmin );
    FLA_Obj_create( dt_real, 1, 1, 0, 0, &rmin );
    FLA_Obj_create( dt_real, 1, 1, 0, 0, &rmax );
 
    // Query safmin, precision.
    FLA_Mach_params( FLA_MACH_PREC,  prec );
    FLA_Mach_params( FLA_MACH_SFMIN, safmin );
 
//FLA_Obj_show( "safmin", safmin, "%20.12e", "" );
//FLA_Obj_show( "prec", prec, "%20.12e", "" );
 
    // rmin = sqrt( safmin ) / prec;
    FLA_Copy( safmin, rmin );
    FLA_Sqrt( rmin );
    FLA_Inv_scal( prec, rmin );
 
    // rmax = 1 / rmin;
    FLA_Copy( rmin, rmax );
    FLA_Invert( FLA_NO_CONJUGATE, rmax );
 
//FLA_Obj_show( "rmin", rmin, "%20.12e", "" );
//FLA_Obj_show( "rmax", rmax, "%20.12e", "" );
 
    // Find the maximum absolute value of A.
    FLA_Max_abs_value( A, norm );
 
    if ( FLA_Obj_gt( norm, FLA_ZERO ) && FLA_Obj_lt( norm, rmin ) )
    {
        // sigma = rmin / norm;
        FLA_Copy( rmin, sigma );
        FLA_Inv_scal( norm, sigma );
    }
    else if ( FLA_Obj_gt( norm, rmax ) )
    {
        // sigma = rmax / norm;
        FLA_Copy( rmax, sigma );
        FLA_Inv_scal( norm, sigma );
    }
    else
    {
        // sigma = 1.0;
        FLA_Copy( FLA_ONE, sigma );
    }
 
    FLA_Obj_free( &norm );
    FLA_Obj_free( &prec );
    FLA_Obj_free( &safmin );
    FLA_Obj_free( &rmin );
    FLA_Obj_free( &rmax );
 
    return FLA_SUCCESS;
}

References FLA_Check_error_level(), FLA_Copy(), FLA_Inv_scal(), FLA_Invert(), FLA_Mach_params(), FLA_Max_abs_value(), FLA_Obj_create(), FLA_Obj_datatype_proj_to_real(), FLA_Obj_free(), FLA_Obj_gt(), FLA_Obj_lt(), FLA_ONE, FLA_Sqrt(), FLA_Svd_compute_scaling_check(), and FLA_ZERO.

Referenced by FLA_Svd_uv_unb_var1(), and FLA_Svd_uv_unb_var2().