LDistance.h

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#pragma once
 
// Standard.
#include <cmath>
#include <cstdlib>
#include <string>
 
// Base code.
#include <Debug.h>
#include <Geometry.h>
 
namespace ttk {
 
  class LDistance : virtual public Debug {
  public:
    LDistance();
 
    template <class dataType>
    int execute(const dataType *const inputData1,
                const dataType *const inputData2,
                dataType *const outputData,
                const std::string &distanceType,
                const SimplexId vertexNumber);
 
    template <class dataType, typename PowerFunc>
    int computeLn(const dataType *const input1,
                  const dataType *const input2,
                  dataType *const output,
                  const int n,
                  const SimplexId vertexNumber,
                  const PowerFunc &powerFunc);
 
    template <class dataType>
    int computeLinf(const dataType *const input1,
                    const dataType *const input2,
                    dataType *const output,
                    const SimplexId vertexNumber);
 
    inline double getResult() {
      return result;
    }
 
    inline void setPrintRes(const bool data) {
      this->printRes = data;
    }
 
    template <typename type>
    static type abs_diff(const type var1, const type var2) {
      return (var1 > var2) ? var1 - var2 : var2 - var1;
    }
 
  protected:
    double result{};
    bool printRes{true};
  };
} // namespace ttk
 
// template functions
template <class dataType>
int ttk::LDistance::execute(const dataType *const inputData1,
                            const dataType *const inputData2,
                            dataType *const outputData,
                            const std::string &distanceType,
                            const SimplexId vertexNumber) {
 
  Timer t;
  int status;
 
// Check variables consistency
#ifndef TTK_ENABLE_KAMIKAZE
  if(inputData1 == nullptr || inputData2 == nullptr) {
    return -1;
  }
#endif
 
  if(distanceType == "inf") {
    status = computeLinf(inputData1, inputData2, outputData, vertexNumber);
  } else {
    int const n = stoi(distanceType);
    if(n < 1)
      return -4;
 
    TTK_POW_LAMBDA(status = computeLn, dataType, n, inputData1, inputData2,
                   outputData, n, vertexNumber);
  }
 
  if(this->printRes) {
    this->printMsg(
      "Data-set processed", 1.0, t.getElapsedTime(), this->threadNumber_);
  }
 
  return status;
}
 
template <class dataType, typename PowerFunc>
int ttk::LDistance::computeLn(const dataType *const input1,
                              const dataType *const input2,
                              dataType *const output,
                              const int n,
                              const ttk::SimplexId vertexNumber,
                              const PowerFunc &powerFunc) {
  dataType sum = 0;
 
// Compute difference for each point.
#ifdef TTK_ENABLE_OPENMP
#pragma omp parallel for num_threads(threadNumber_) reduction(+ : sum)
#endif
  for(ttk::SimplexId i = 0; i < vertexNumber; ++i) {
    const dataType diff = abs_diff<dataType>(input1[i], input2[i]);
    const dataType power = powerFunc(diff);
 
    // Careful: huge dataset + huge values
    // may exceed double capacity.
    sum += power;
 
    // Store difference.
    if(output)
      output[i] = power;
  }
 
  sum = Geometry::pow(sum, 1.0 / (double)n);
 
  // Affect result.
  result = (double)sum;
  if(this->printRes) {
    this->printMsg("L" + std::to_string(n)
                   + "-distance: " + std::to_string(result));
  }
 
  return 0;
}
 
template <class dataType>
int ttk::LDistance::computeLinf(const dataType *const input1,
                                const dataType *const input2,
                                dataType *const output,
                                const ttk::SimplexId vertexNumber) {
  if(vertexNumber < 1)
    return 0;
 
  dataType maxValue = abs_diff<dataType>(input1[0], input2[0]);
 
// Compute difference for each point.
#ifdef TTK_ENABLE_OPENMP
#pragma omp parallel for num_threads(threadNumber_) reduction(max : maxValue)
#endif
  for(ttk::SimplexId i = 1; i < vertexNumber; ++i) {
    const dataType iter = abs_diff<dataType>(input1[i], input2[i]);
    if(iter > maxValue)
      maxValue = iter;
 
    // Store absolute difference in output.
    if(output)
      output[i] = iter;
  }
 
  // Affect result.
  result = (double)maxValue;
  if(this->printRes) {
    this->printMsg("Linf-distance: " + std::to_string(result));
  }
 
  return 0;
}