Refactor: ScalarFresnelMap now maintains a cache (hash map) of calculated Fresnel coefficients

Core/Computation/MainComputation.cpp

@@ -92,7 +92,7 @@ void MainComputation::runProtected()
 }
 
 IFresnelMap* MainComputation::createFresnelMap(const MultiLayer* p_multilayer,
-                                                      const MultiLayer* p_inverted_multilayer)
+                                               const MultiLayer* p_inverted_multilayer)
 {
         if (!p_multilayer->requiresMatrixRTCoefficients())
             return new ScalarFresnelMap(p_multilayer);

Core/Computation/MainComputation.h

@@ -55,7 +55,7 @@ public:
 private:
     void runProtected();
     static IFresnelMap* createFresnelMap(const MultiLayer* p_multilayer,
-                                                const MultiLayer* p_inverted_multilayer);
+                                         const MultiLayer* p_inverted_multilayer);
 
     std::unique_ptr<MultiLayer> mP_multi_layer;
     std::unique_ptr<MultiLayer> mP_inverted_multilayer;

Core/Multilayer/HashKVector.cpp

+// ************************************************************************** //
+//
+//  BornAgain: simulate and fit scattering at grazing incidence
+//
+//! @file      Core/Computation/HashKVector.cpp
+//! @brief     Implements class HashKVector.
+//!
+//! @homepage  http://www.bornagainproject.org
+//! @license   GNU General Public License v3 or higher (see COPYING)
+//! @copyright Forschungszentrum Jülich GmbH 2017
+//! @authors   Scientific Computing Group at MLZ Garching
+//! @authors   J. Burle, J. M. Fisher, M. Ganeva, G. Pospelov, W. Van Herck, J. Wuttke
+//
+// ************************************************************************** //
+
+#include "HashKVector.h"
+
+// Simple exclusive or of the std::hash<double> of its components
+size_t HashKVector::operator()(kvector_t kvec) const noexcept
+{
+    return m_double_hash(kvec.x()) ^ m_double_hash(kvec.y()) ^ m_double_hash(kvec.z());
+}

Core/Multilayer/HashKVector.h

+// ************************************************************************** //
+//
+//  BornAgain: simulate and fit scattering at grazing incidence
+//
+//! @file      Core/Computation/HashKVector.h
+//! @brief     Defines class HashKVector.
+//!
+//! @homepage  http://www.bornagainproject.org
+//! @license   GNU General Public License v3 or higher (see COPYING)
+//! @copyright Forschungszentrum Jülich GmbH 2017
+//! @authors   Scientific Computing Group at MLZ Garching
+//! @authors   J. Burle, J. M. Fisher, M. Ganeva, G. Pospelov, W. Van Herck, J. Wuttke
+//
+// ************************************************************************** //
+
+#ifndef HASHKVECTOR_H
+#define HASHKVECTOR_H
+
+#include "Vectors3D.h"
+#include <functional>
+
+class HashKVector
+{
+public:
+    HashKVector() {}
+    ~HashKVector() {}
+
+    size_t operator()(kvector_t kvec) const noexcept;
+private:
+    std::hash<double> m_double_hash;
+};
+
+#endif // HASHKVECTOR_H

Core/Multilayer/ScalarFresnelMap.cpp

@@ -23,6 +23,9 @@ ScalarFresnelMap::ScalarFresnelMap(const MultiLayer* multilayer)
     : mp_multilayer(multilayer)
 {}
 
+ScalarFresnelMap::~ScalarFresnelMap()
+{}
+
 const ILayerRTCoefficients* ScalarFresnelMap::getOutCoefficients(
         const SimulationElement& sim_element, size_t layer_index) const
 {
@@ -38,7 +41,15 @@ const ILayerRTCoefficients* ScalarFresnelMap::getInCoefficients(
 const ScalarRTCoefficients* ScalarFresnelMap::getCoefficients(
         kvector_t kvec, size_t layer_index) const
 {
-    SpecularMatrix::MultiLayerCoeff_t coeffs;
-    SpecularMatrix::execute(*mp_multilayer, kvec, coeffs);
-    return new ScalarRTCoefficients(coeffs[layer_index]);
+    ScalarRTCoefficients* result;
+    auto it = m_hash_table.find(kvec);
+    if (it != m_hash_table.end())
+        result = new ScalarRTCoefficients(it->second[layer_index]);
+    else {
+        std::vector<ScalarRTCoefficients> coeffs;
+        SpecularMatrix::execute(*mp_multilayer, kvec, coeffs);
+        result = new ScalarRTCoefficients(coeffs[layer_index]);
+        m_hash_table[kvec] = std::move(coeffs);
+    }
+    return result;
 }

Core/Multilayer/ScalarFresnelMap.h

@@ -16,8 +16,10 @@
 #ifndef SCALARFRESNELMAP_H
 #define SCALARFRESNELMAP_H
 
+#include "HashKVector.h"
 #include "IFresnelMap.h"
-#include "Vectors3D.h"
+#include <unordered_map>
+#include <vector>
 
 class MultiLayer;
 class ILayerRTCoefficients;
@@ -31,7 +33,7 @@ class BA_CORE_API_ ScalarFresnelMap : public IFresnelMap
 {
 public:
     ScalarFresnelMap(const MultiLayer* multilayer);
-    ~ScalarFresnelMap() final {}
+    ~ScalarFresnelMap() final;
 
     //! Retrieves the amplitude coefficients for the given angles
     const ILayerRTCoefficients* getOutCoefficients (
@@ -44,6 +46,8 @@ public:
 private:
     const MultiLayer* mp_multilayer;
     const ScalarRTCoefficients* getCoefficients(kvector_t kvec, size_t layer_index) const;
+    mutable std::unordered_map<kvector_t, std::vector<ScalarRTCoefficients>,
+                               HashKVector> m_hash_table;
 };
 
 #endif // SCALARFRESNELMAP_H