STYLE: [Versor|VersorRigid3D]TransformOptimizer same

Make the two nearly identical classes formatted
as close to the same as possible.  This reveals
that the two classes are nearly identical.

The next patch set will remove the
VersorRigid3D specialization.

Modules/Numerics/Optimizers/include/itkVersorRigid3DTransformOptimizer.h

@@ -28,18 +28,20 @@ namespace itk
  * \brief Implement a gradient descent optimizer for the VersorRigid3DTransform
  * parameter space.
  *
- * VersorRigid3DTransformOptimizer is a variant of the gradient descent
- * optimizer implemented in RegularStepGradientDescentOptimizer.
+ * VersorRigid3DTransformOptimizer is a variant of the
+ * gradient descent optimizer implemented in
+ * RegularStepGradientDescentOptimizer.
  *
- * Versors are not in a vector space, for that reason, the classical gradient
- * descent algorithm has to be modified in order to be applicable to Versors
- * (unit quaternions) that form the group SO(3).
+ * Versors are not in a vector space, for that reason,
+ * the classical gradient descent algorithm has to be
+ * modified in order to be applicable to Versors (unit
+ * quaternions) that form the group SO(3).
  *
- * The Versor space has only three degrees of freedom, even though Versors are
- * represented using four values.
+ * The Versor space has only three degrees of freedom,
+ * even though Versors are represented using four values.
  *
- * This optimizer assumes that the CostFunction to be optimized has an
- * itk::Versor and an itk::Vector as parameters.
+ * This optimizer assumes that the CostFunction to be
+ * optimized has an itk::Versor as parameters.
  *
  * \sa RegularStepGradientDescentOptimizer
  * \sa Versor
@@ -65,9 +67,6 @@ class ITKOptimizers_EXPORT VersorRigid3DTransformOptimizer : public RegularStepG
   /** Run-time type information (and related methods). */
   itkTypeMacro(VersorRigid3DTransformOptimizer, RegularStepGradientDescentBaseOptimizer);
 
-  /** This class is specialized for 3D  */
-  static constexpr unsigned int SpaceDimension = 6;
-
   /**  Versor Type  */
   using VersorType = Versor<double>;
   using VectorType = VersorType::VectorType;

Modules/Numerics/Optimizers/include/itkVersorTransformOptimizer.h

@@ -40,7 +40,7 @@ namespace itk
  * even though Versors are represented using four values.
  *
  * This optimizer assumes that the CostFunction to be
- * optimized has an itk::Versor as parameter.
+ * optimized has an itk::Versor as parameters.
  *
  * \sa RegularStepGradientDescentOptimizer
  * \sa Versor

Modules/Numerics/Optimizers/src/itkVersorRigid3DTransformOptimizer.cxx

@@ -27,7 +27,8 @@ namespace itk
 void
 VersorRigid3DTransformOptimizer::StepAlongGradient(double factor, const DerivativeType & transformedGradient)
 {
-  const ParametersType & currentPosition = this->GetCurrentPosition();
+  const ParametersType &        currentPosition = this->GetCurrentPosition();
+  static constexpr unsigned int NumberOfParameters = 6;
 
   // The parameters are assumed to be the right part of the versor and the
   // components of the translation vector.
@@ -66,16 +67,17 @@ VersorRigid3DTransformOptimizer::StepAlongGradient(double factor, const Derivati
   //
   VersorType newRotation = currentRotation * gradientRotation;
 
-  ParametersType newParameters(SpaceDimension);
+  ParametersType newParameters(NumberOfParameters);
 
   newParameters[0] = newRotation.GetX();
   newParameters[1] = newRotation.GetY();
   newParameters[2] = newRotation.GetZ();
 
-  // Now do the typical update for a Vector space.
-  for (unsigned int k = 3; k < 6; ++k)
+  // Optimize the non-versor parameters as the
+  // RegularStepGradientDescentOptimizer
+  for (unsigned int j = 3; j < NumberOfParameters; ++j)
   {
-    newParameters[k] = currentPosition[k] + transformedGradient[k] * factor;
+    newParameters[j] = currentPosition[j] + transformedGradient[j] * factor;
   }
 
   this->SetCurrentPosition(newParameters);

Modules/Numerics/Optimizers/src/itkVersorTransformOptimizer.cxx

@@ -28,9 +28,10 @@ void
 VersorTransformOptimizer::StepAlongGradient(double factor, const DerivativeType & transformedGradient)
 {
   const ParametersType & currentPosition = this->GetCurrentPosition();
-  unsigned int           NumberOfParameters = m_CostFunction->GetNumberOfParameters();
+  const unsigned int     NumberOfParameters = m_CostFunction->GetNumberOfParameters();
 
-  // The parameters are assumed to be the right part of the versor
+  // The parameters are assumed to be the right part of the versor and the
+  // components of the translation vector.
   //
   VectorType rightPart;