Introduce member to set numerical gradient step size and set COMPTEL gradient step size to 0.05 deg.

Jürgen Knödlseder
1 parent 5ce52967
Showing 3 changed files with 42 additions and 34 deletions
include/GObservation.hpp
inst/com/src/GCOMObservation.cpp
src/obs/GObservation.cpp
@@ -117,6 +117,7 @@ public:
     virtual double           npred_grad(const GModel&    model,
                                         const GModelPar& par) const;
     virtual void             remove_response_cache(const std::string& name);
+    virtual const double&    grad_step_size(void) const;
  
     // Implemented methods
     bool               has_events(void) const;
@@ -218,10 +219,11 @@ protected:
     };
  
     // Protected data area
-    std::string m_name;        //!< Observation name
-    std::string m_id;          //!< Observation identifier
-    std::string m_statistic;   //!< Optimizer statistic
-    GEvents*    m_events;      //!< Pointer to event container
+    std::string m_name;           //!< Observation name
+    std::string m_id;             //!< Observation identifier
+    std::string m_statistic;      //!< Optimizer statistic
+    GEvents*    m_events;         //!< Pointer to event container
+    double      m_grad_step_size; //!< Gradient step size
  
     // Stack of identifiers of parameters with gradients
     mutable std::vector<std::string> m_pars_with_gradients;
@@ -320,4 +322,16 @@ const std::string&amp; GObservation::statistic(void) const
     return (m_statistic);
 }
  
+
+/***********************************************************************//**
+ * @brief Return gradient step size
+ *
+ * @return Gradient step size.
+ ***************************************************************************/
+inline
+const double& GObservation::grad_step_size(void) const
+{
+    return (m_grad_step_size);
+}
+
 #endif /* GOBSERVATION_HPP */
@@ -868,6 +868,11 @@ std::string GCOMObservation::print(const GChatter&amp; chatter) const
  ***************************************************************************/
 void GCOMObservation::init_members(void)
 {
+    // Initialise gradient step size to 0.05 degrees since the angular
+    // resolution of COMPTEL is much worse than the default step size
+    // value of 0.0002.
+    m_grad_step_size = 0.05;
+
     // Initialise members
     m_instrument = "COM";
     m_response.clear();
@@ -875,12 +875,6 @@ double GObservation::npred(const GModel&amp; model) const
  * a simple method as this method is likely used for spatial model parameters,
  * and the spatial model may eventually be noisy due to numerical integration
  * limits.
- *
- * The step size for the simple method has been fixed to 0.0002, which
- * corresponds to about 1 arcsec for parameters that are given in degrees.
- * The reasoning behind this value is that parameters that use numerical
- * gradients are typically angles, such as for example the position, and
- * we want to achieve arcsec precision with this method.
  ***************************************************************************/
 double GObservation::model_grad(const GModel&    model,
                                 const GModelPar& par,
@@ -901,10 +895,8 @@ double GObservation::model_grad(const GModel&amp;    model,
         // Get actual parameter value
         double x = par.factor_value();
  
-        // Set fixed step size for computation of derivative.
-        // By default, the step size is fixed to 0.0002.
-        const double step_size = 0.0002; // ~1 arcsec
-        double       h         = step_size;
+        // Set step size for computation of derivative.
+        double h = m_grad_step_size;
  
         // Re-adjust the step-size h in case that the initial step size is
         // larger than the allowed parameter range 
@@ -965,12 +957,6 @@ double GObservation::model_grad(const GModel&amp;    model,
  * a simple method as this method is likely used for spatial model parameters,
  * and the spatial model may eventually be noisy due to numerical integration
  * limits.
- *
- * The step size for the simple method has been fixed to 0.0002, which
- * corresponds to about 1 arcsec for parameters that are given in degrees.
- * The reasoning behind this value is that parameters that use numerical
- * gradients are typically angles, such as for example the position, and
- * we want to achieve arcsec precision with this method.
  ***************************************************************************/
 GVector GObservation::model_grad(const GModel&    model,
                                  const GModelPar& par) const
@@ -990,10 +976,8 @@ GVector GObservation::model_grad(const GModel&amp;    model,
         // Get actual parameter value
         double x = par.factor_value();
  
-        // Set fixed step size for computation of derivative.
-        // By default, the step size is fixed to 0.0002.
-        const double step_size = 0.0002; // ~1 arcsec
-        double       h         = step_size;
+        // Set step size for computation of derivative.
+        double h = m_grad_step_size;
  
         // Re-adjust the step-size h in case that the initial step size is
         // larger than the allowed parameter range
@@ -1114,8 +1098,6 @@ GVector GObservation::model_grad(const GModel&amp;    model,
  * a simple method as this method is likely used for spatial model parameters,
  * and the spatial model may eventually be noisy due to numerical integration
  * limits.
- *
- * The step size for the simple method has been fixed to 0.0002.
  ***************************************************************************/
 double GObservation::npred_grad(const GModel& model, const GModelPar& par) const
 {
@@ -1134,9 +1116,8 @@ double GObservation::npred_grad(const GModel&amp; model, const GModelPar&amp; par) const
         // Get actual parameter value
         double x = par.factor_value();
  
-        // Set fixed step size to 0.0002 for computation of derivative.
-        const double step_size = 0.0002;
-        double       h         = step_size;
+        // Set step size for computation of derivative.
+        double h = m_grad_step_size;
  
         // Re-adjust the step-size h in case that the initial step size is
         // larger than the allowed parameter range 
@@ -1285,14 +1266,21 @@ void GObservation::computed_gradient(const GModel&amp; model, const GModelPar&amp; par) 
  
 /***********************************************************************//**
  * @brief Initialise class members
+ *
+ * The step size for gradient computation is fixed by default to 0.0002
+ * degrees, which corresponds to about 1 arcsec for parameters that are
+ * given in degrees. The reasoning behind this value is that parameters that
+ * use numerical gradients are typically angles, such as for example the
+ * position, and we want to achieve arcsec precision with this method.
  ***************************************************************************/
 void GObservation::init_members(void)
 {
     // Initialise members
     m_name.clear();
     m_id.clear();
-    m_statistic = "cstat";
-    m_events    = NULL;
+    m_statistic      = "cstat";
+    m_events         = NULL;
+    m_grad_step_size = 0.0002;
  
     // Initialise stack of identifiers of parameters with gradients
     m_pars_with_gradients.clear();
@@ -1312,9 +1300,10 @@ void GObservation::init_members(void)
 void GObservation::copy_members(const GObservation& obs)
 {
     // Copy members
-    m_name      = obs.m_name;
-    m_id        = obs.m_id;
-    m_statistic = obs.m_statistic;
+    m_name           = obs.m_name;
+    m_id             = obs.m_id;
+    m_statistic      = obs.m_statistic;
+    m_grad_step_size = obs.m_grad_step_size;
  
     // Copy stack of identifiers of parameters with gradients
     m_pars_with_gradients = obs.m_pars_with_gradients;