Merge pull request #503 from sujithvm/issue_439

Adds simple adjugate function, fixes #439.

Author: translunar

lib/nmatrix/math.rb

@@ -112,6 +112,55 @@ def invert
   end
   alias :inverse :invert
 
+  #
+  # call-seq:
+  #     adjugate! -> NMatrix
+  #
+  # Calculate the adjugate of the matrix (in-place). 
+  # Only works on dense matrices. 
+  #
+  # * *Raises* :
+  #   - +StorageTypeError+ -> only implemented on dense matrices.
+  #   - +ShapeError+ -> matrix must be square.
+  #   - +DataTypeError+ -> cannot calculate adjugate of an integer matrix in-place.
+  #
+  def adjugate!
+    raise(StorageTypeError, "adjugate only works on dense matrices currently") unless self.dense?
+    raise(ShapeError, "Cannot calculate adjugate of a non-square matrix") unless self.dim == 2 && self.shape[0] == self.shape[1]
+    raise(DataTypeError, "Cannot calculate adjugate of an integer matrix in-place") if self.integer_dtype?
+    d = self.det
+    self.invert!
+    self.map! { |e| e * d } 
+    self
+  end
+  alias :adjoint! :adjugate!
+
+  #
+  # call-seq:
+  #     adjugate -> NMatrix
+  #
+  # Make a copy of the matrix and calculate the adjugate of the matrix. 
+  # Only works on dense matrices. 
+  #
+  # * *Returns* :
+  #   - A dense NMatrix. Will be the same type as the input NMatrix,
+  #   except if the input is an integral dtype, in which case it will be a
+  #   :float64 NMatrix. 
+  #
+  # * *Raises* :
+  #   - +StorageTypeError+ -> only implemented on dense matrices.
+  #   - +ShapeError+ -> matrix must be square.
+  #
+  def adjugate
+    raise(StorageTypeError, "adjugate only works on dense matrices currently") unless self.dense?
+    raise(ShapeError, "Cannot calculate adjugate of a non-square matrix") unless self.dim == 2 && self.shape[0] == self.shape[1]
+    d = self.det
+    mat = self.invert
+    mat.map! { |e| e * d }    
+    mat 
+  end
+  alias :adjoint :adjugate
+
   #
   # call-seq:
   #     getrf! -> Array

spec/math_spec.rb

@@ -478,6 +478,49 @@
     end
   end
 
+  ALL_DTYPES.each do |dtype|
+    next if dtype == :byte #doesn't work for unsigned types
+    next if dtype == :object
+
+    context dtype do
+      err = case dtype
+              when :float32, :complex64
+                1e-4
+              else #integer matrices will return :float64
+                1e-13
+            end
+
+      it "should correctly find adjugate a matrix in place (bang)" do
+        a = NMatrix.new(:dense, 2, [2, 3, 3, 5], dtype)
+        b = NMatrix.new(:dense, 2, [5, -3, -3, 2], dtype)
+
+        if a.integer_dtype?
+          expect{a.adjugate!}.to raise_error(DataTypeError)
+        else
+          #should return adjugate as well as modifying a
+          r = a.adjugate!
+          expect(a).to be_within(err).of(b)
+          expect(r).to be_within(err).of(b)
+        end
+      end
+
+
+      it "should correctly find adjugate of a matrix out-of-place" do
+        a = NMatrix.new(:dense, 3, [-3, 2, -5, -1, 0, -2, 3, -4, 1], dtype)
+
+        if a.integer_dtype?
+          b = NMatrix.new(:dense, 3, [-8, 18, -4, -5, 12, -1, 4, -6, 2], :float64)
+        else
+          b = NMatrix.new(:dense, 3, [-8, 18, -4, -5, 12, -1, 4, -6, 2], dtype)
+        end
+
+        expect(a.adjoint).to be_within(err).of(b)
+        expect(a.adjugate).to be_within(err).of(b)
+      end
+
+    end
+  end
+
   # TODO: Get it working with ROBJ too
   [:byte,:int8,:int16,:int32,:int64,:float32,:float64].each do |left_dtype|
     [:byte,:int8,:int16,:int32,:int64,:float32,:float64].each do |right_dtype|