lib/compsci/simplex.rb in compsci-0.3.1.1 vs lib/compsci/simplex.rb in compsci-0.3.2.1

@@ -24,39 +24,40 @@
     raise(ArgumentError, "a doesn't match c") unless a.first.size == num_vars
 
     @max_pivots = DEFAULT_MAX_PIVOTS
 
     # Problem dimensions; these never change
-    @num_non_slack_vars = num_vars
-    @num_constraints    = num_inequalities
-    @num_vars           = @num_non_slack_vars + @num_constraints
+    @num_free_vars   = num_vars
+    @num_basic_vars = num_inequalities
+    @total_vars      = @num_free_vars + @num_basic_vars
 
     # Set up initial matrix A and vectors b, c
-    @c = c.map { |flt| -1 * flt } + Array.new(@num_constraints, 0)
+    # store all input values as Rational (via #rationalize)
+    @c = c.map { |flt| -1 * flt.rationalize } + Array.new(@num_basic_vars, 0)
     @a = a.map.with_index { |ary, i|
-      if ary.size != @num_non_slack_vars
+      if ary.size != @num_free_vars
         raise ArgumentError, "a is inconsistent"
       end
-      # set diagonal to 1 (identity matrix?)
-      ary + Array.new(@num_constraints) { |ci| ci == i ? 1 : 0 }
+      # add identity matrix
+      ary.map { |flt| flt.rationalize } +
+        Array.new(@num_basic_vars) { |ci| ci == i ? 1 : 0 }
     }
-    @b = b
+    @b = b.map { |flt| flt.rationalize }
 
-    # set initial solution: all non-slack variables = 0
-    @basic_vars = (@num_non_slack_vars...@num_vars).to_a
+    @basic_vars = (@num_free_vars...@total_vars).to_a
     self.update_solution
   end
 
   # does not modify vector / matrix
   def update_solution
-    @x = Array.new(@num_vars, 0)
+    @x = Array.new(@total_vars, 0)
 
     @basic_vars.each { |basic_var|
       idx = nil
-      @num_constraints.times { |i|
+      @num_basic_vars.times { |i|
         if @a[i][basic_var] == 1
-          idx =i
+          idx = i
           break
         end
       }
       raise(SanityCheck, "no idx for basic_var #{basic_var} in a") unless idx
       @x[basic_var] = @b[idx]
@@ -76,11 +77,11 @@
       self.pivot
     end
   end
 
   def current_solution
-    @x[0...@num_non_slack_vars]
+    @x[0...@num_free_vars]
   end
 
   def can_improve?
     !self.entering_variable.nil?
   end
@@ -119,11 +120,11 @@
     @c = @c.map.with_index { |val, i|
       val - @c[pivot_column] * @a[pivot_row][i]
     }
 
     # update A and B
-    @num_constraints.times { |i|
+    @num_basic_vars.times { |i|
       next if i == pivot_row
       r = @a[i][pivot_column]
       @a[i] = @a[i].map.with_index { |val, j| val - r * @a[pivot_row][j] }
       @b[i] = @b[i] - r * @b[pivot_row]
     }
@@ -132,10 +133,10 @@
   end
 
   def pivot_row(column_ix)
     min_ratio = nil
     idx = nil
-    @num_constraints.times { |i|
+    @num_basic_vars.times { |i|
       a, b = @a[i][column_ix], @b[i]
       next if a == 0 or (b < 0) ^ (a < 0)
       ratio = Rational(b, a)
       idx, min_ratio = i, ratio if min_ratio.nil? or ratio <= min_ratio
     }