Function GMP::Column::GetLowerBound(GMP, column)

GMP::Column::GetLowerBound

The function GMP::Column::GetLowerBound returns the lower bound of a column in the generated mathematical program.

GMP::Column::GetLowerBound(
     GMP,            ! (input) a generated mathematical program
     column          ! (input) a scalar reference or column number
     )

Arguments

GMP

An element in AllGeneratedMathematicalPrograms.

column

A scalar reference to an existing column in the matrix or an element in the set Integers in the range \(\{ 0 .. n-1 \}\) where \(n\) is the number of columns in the matrix.

Return Value

The lower bound value for the specified column.

Note

• If the column has a unit then the scaled lower bound is returned (without unit).

• This function can be used to retrieve the lower bound after presolving in case the GMP was created by GMP::Instance::CreatePresolved, even if the column was deleted by the AIMMS Presolver.

Example

Assume that ‘x1’ is a variable in mathematical program ‘MP’ with a unit as defined by:

Quantity SI_Mass {
    BaseUnit      :  kg;
    Conversions   :  ton -> kg : # -> # * 1000;
}
Parameter min_wght {
    Unit          :  ton;
    InitialValue  :  20;
}
Variable x1 {
    Range         :  [min_wght, inf);
    Unit          :  ton;
}

If we want to multiply the lower bound by 1.5 and assign it as the new value by using function GMP::Column::SetLowerBound we can use

lb1 := 1.5 * (GMP::Column::GetLowerBound( 'MP', x1 )) [ton];

GMP::Column::SetLowerBound( 'MP', x1, lb1 );

if ‘lb1’ is a parameter with unit [ton], or we can use

lb2 := 1.5 * GMP::Column::GetLowerBound( 'MP', x1 );

GMP::Column::SetLowerBound( 'MP', x1, lb2 * GMP::Column::GetScale( 'MP', x1 ) );

if ‘lb2’ is a parameter without a unit.

See also

The routines GMP::Instance::Generate, GMP::Column::SetLowerBound, GMP::Column::GetUpperBound, GMP::Column::GetScale and GMP::Instance::CreatePresolved.