SplineHelper.h

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// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
// All rights not expressly granted are reserved.
//
// This software is distributed under the terms of the GNU General Public
// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
//
// In applying this license CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
 
 
#ifndef ALICEO2_GPUCOMMON_TPCFASTTRANSFORMATION_SPLINEHELPER_H
#define ALICEO2_GPUCOMMON_TPCFASTTRANSFORMATION_SPLINEHELPER_H
 
#include <cmath>
#include <vector>
 
#include "GPUCommonDef.h"
#include "Rtypes.h"
#include "TString.h"
#include "Spline1D.h"
#include "Spline.h"
#include "Spline1DHelperOld.h"
#include <functional>
 
namespace o2::gpu
{
 
template <typename DataT>
class SplineHelper
{
 public:
 
  SplineHelper();
 
  SplineHelper(const SplineHelper&) = delete;
 
  SplineHelper& operator=(const SplineHelper&) = delete;
 
  ~SplineHelper() = default;
 
 
  void approximateFunction(SplineContainer<DataT>& spline,
                           const double xMin[/* Xdim */], const double xMax[/* Xdim */],
                           std::function<void(const double x[/* Xdim */], double f[/* Fdim */])> F,
                           const int32_t nAxiliaryDataPoints[/* Xdim */] = nullptr);
 
 
  int32_t setSpline(const SplineContainer<DataT>& spline, const int32_t nAxiliaryPoints[/* Xdim */]);
 
  void approximateFunction(
    DataT* Fparameters, const double xMin[/* mXdimensions */], const double xMax[/* mXdimensions */],
    std::function<void(const double x[/* mXdimensions */], double f[/* mFdimensions */])> F) const;
 
  void approximateFunctionBatch(
    DataT* Fparameters, const double xMin[/* mXdimensions */], const double xMax[/* mXdimensions */],
    std::function<void(const std::vector<double> x[/* mXdimensions */], double f[/*mFdimensions*/])> F,
    uint32_t batchsize) const;
 
  void approximateFunction(
    DataT* Fparameters, const double DataPointF[/*getNumberOfDataPoints() x nFdim*/]) const;
 
  int32_t getNumberOfDataPoints(int32_t dimX) const { return mHelpers[dimX].getNumberOfDataPoints(); }
 
  int32_t getNumberOfDataPoints() const { return mNumberOfDataPoints; }
 
  const Spline1DHelperOld<DataT>& getHelper(int32_t dimX) const { return mHelpers[dimX]; }
 
 
  const char* getLastError() const { return mError.Data(); }
 
#if !defined(GPUCA_GPUCODE) && !defined(GPUCA_STANDALONE)
  static int32_t test(const bool draw = 0, const bool drawDataPoints = 1);
#endif
 
  static int32_t arraytopoints(int32_t point, int32_t result[], const int32_t numbers[], int32_t dim);
 
  static int32_t pointstoarray(const int32_t indices[], const int32_t numbers[], int32_t dim);
 
 private:
  int32_t storeError(Int_t code, const char* msg);
 
  TString mError = "";         
  int32_t mXdimensions;        
  int32_t mFdimensions;        
  int32_t mNumberOfParameters; 
  int32_t mNumberOfDataPoints; 
  std::vector<Spline1DHelperOld<DataT>> mHelpers;
};
 
template <typename DataT>
void SplineHelper<DataT>::approximateFunction(
  SplineContainer<DataT>& spline,
  const double xMin[/* Xdim */], const double xMax[/* Xdim */],
  std::function<void(const double x[/* Xdim */], double f[/* Fdim */])> F,
  const int32_t nAxiliaryDataPoints[/* Xdim */])
{
  setSpline(spline, nAxiliaryDataPoints);
  approximateFunction(spline.getParameters(), xMin, xMax, F);
  DataT xxMin[spline.getXdimensions()];
  DataT xxMax[spline.getXdimensions()];
  for (int32_t i = 0; i < spline.getXdimensions(); i++) {
    xxMin[i] = xMin[i];
    xxMax[i] = xMax[i];
  }
  spline.setXrange(xxMin, xxMax);
}
 
template <typename DataT>
int32_t SplineHelper<DataT>::setSpline(
  const SplineContainer<DataT>& spline, const int32_t nAxiliaryPoints[/* Xdim */])
{
  // Prepare creation of an irregular spline
  // The should be at least one (better, two) axiliary measurements on each segnment between two knots and at least 2*nKnots measurements in total
  // Returns 0 when the spline can not be constructed with the given nAxiliaryPoints
 
  int32_t ret = 0;
  mXdimensions = spline.getXdimensions();
  mFdimensions = spline.getYdimensions();
  mNumberOfParameters = spline.getNumberOfParameters();
  mNumberOfDataPoints = 1;
  mHelpers.clear();
  mHelpers.resize(mXdimensions);
  for (int32_t i = 0; i < mXdimensions; i++) {
    int32_t np = (nAxiliaryPoints != nullptr) ? nAxiliaryPoints[i] : 4;
    if (mHelpers[i].setSpline(spline.getGrid(i), mFdimensions, np) != 0) {
      ret = storeError(-2, "SplineHelper::setSpline: error by setting an axis");
    }
    mNumberOfDataPoints *= mHelpers[i].getNumberOfDataPoints();
  }
 
  return ret;
}
 
} // namespace o2::gpu
 
#endif