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lib/Algorithm/Simplex.pm  view on Meta::CPAN

=head2 determine_bland_pivot_row_number

Find the pivot row using Bland ordering technique to prevent cycles.

=cut

sub determine_bland_pivot_row_number {
    my ($self, $positive_ratios, $positive_ratio_row_numbers) = @_;

    # Now that we have the ratios and their respective rows we can find the min
    # and then select the lowest bland min if there are ties.
    my @min_indices = $self->min_index($positive_ratios);
    my @min_ratio_row_numbers =
      map { $positive_ratio_row_numbers->[$_] } @min_indices;
    my @bland_number_for_min_ratio_rows;
    foreach my $row_number (@min_ratio_row_numbers) {
        push @bland_number_for_min_ratio_rows,
          $self->get_bland_number_for('y', $row_number);
    }

# Pass blands number to routine that returns index of location where minimum bland occurs.

lib/Algorithm/Simplex/Float.pm  view on Meta::CPAN

=cut

sub determine_simplex_pivot_columns {
    my $self = shift;

    my @simplex_pivot_column_numbers;

# Assumes the existence of at least one pivot (use optimality check to insure this)
# According to Nering and Tucker (1993) page 26
# "selected a column with a positive entry in the basement row."
# NOTE: My intuition indicates a pivot could still take place but no gains would be made
# when the cost is zero.  This would not lead us to optimality, but if we were
# already in an optimal state if may (should) lead to another optimal state.
# This would only apply then in the optimal case, i.e. all entries non-positive.
    for my $col_num (0 .. $self->number_of_columns - 1) {
        if ($self->tableau->[ $self->number_of_rows ]->[$col_num] >
            $self->EPSILON)
        {
            push(@simplex_pivot_column_numbers, $col_num);
        }