floating point equality check

[johnkolen]

In Simplex#update_solution, there is a float/integer equality check that fails occasionally:

  def update_solution
    0.upto(@num_vars - 1) {|i| @x[i] = 0 }

    @basic_vars.each do |basic_var|
      row_with_1 = row_indices.detect do |row_ix|
        @a[row_ix][basic_var] == 1
      end
      @x[basic_var] = @b[row_with_1]
    end
  end

The failure occurs when the coefficient for a basic variable is very close to 1 (e.g. 0.9999999999999). I've monkey patched mine with an epsilon check and it works as expected.
Note, it will still throw an error if it can't find any rows. I haven't dug into the code to see if it's possible.