Grid.h

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//////////////////////////////////////////////////////////////////////////////////////
// This file is distributed under the University of Illinois/NCSA Open Source License.
// See LICENSE file in top directory for details.
//
// Copyright (c) 2016 Jeongnim Kim and QMCPACK developers.
//
// File developed by: Paul R. C. Kent, kentpr@ornl.gov, Oak Ridge National Laboratory
//                    Mark A. Berrill, berrillma@ornl.gov, Oak Ridge National Laboratory
//
// File created by: Paul R. C. Kent, kentpr@ornl.gov, Oak Ridge National Laboratory
//////////////////////////////////////////////////////////////////////////////////////


//           http://pathintegrals.info                     //
/////////////////////////////////////////////////////////////

#ifndef GRID_H
#define GRID_H

#include "IO.h"

#include "Blitz.h"

using IO::IOSectionClass;

//Ken's Grid Class

/// The different types of grids that we currently allow
typedef enum
{
  NONE,
  LINEAR,
  OPTIMAL,
  OPTIMAL2,
  LOG,
  CLUSTER,
  GENERAL,
  CENTER
} GridType;


/// Parent class for all grids
class Grid
{
protected:
  /// Contains the grid points
  Array<double, 1> grid;

public:
  /// First and last grid points
  double Start, End;

  /// Number of points in the grid
  int NumPoints;

  /// The i'th point in the grid
  inline double operator()(int i) const { return (grid(i)); }
  inline double* data() { return grid.data(); }
  inline Array<double, 1>& Points() { return grid; }

  /// Returns the type of the grid (i.e. linear, optimal, etc)
  virtual GridType Type() = 0;

  ///Returns the index of the nearest point below r.
  virtual int ReverseMap(double r)             = 0;
  virtual void Write(IOSectionClass& out)      = 0;
  virtual void Read(IOSectionClass& inSection) = 0;
  virtual ~Grid(){}
};


/// Linear Grid inherets from Grid.
class LinearGrid : public Grid
{
private:
  /// The value between successive grid points.
  double delta, deltainv;
  inline void CheckRoundingMode();

public:
  /// Returns the type of the grid (in this case LINEAR)
  GridType Type() override { return (LINEAR); }

  /// Returns the index of the nearest point below r.
  int ReverseMap(double r) override { return ((int)nearbyint((r - Start) * deltainv - 0.5)); }

  /// Initializes the linear grid.
  inline void Init(double start, double end, int numpoints)
  {
    Start     = start;
    End       = end;
    NumPoints = numpoints;
    grid.resize(NumPoints);
    delta    = (End - Start) / (double)(NumPoints - 1);
    deltainv = 1.0 / delta;
    for (int i = 0; i < NumPoints; i++)
      grid(i) = Start + (double)i * delta;
    CheckRoundingMode();
  }

  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("Linear"));
    outSection.WriteVar("Start", Start);
    outSection.WriteVar("End", End);
    outSection.WriteVar("NumPoints", NumPoints);
  }

  void Read(IOSectionClass& inSection) override
  {
    assert(inSection.ReadVar("Start", Start));
    assert(inSection.ReadVar("End", End));
    assert(inSection.ReadVar("NumPoints", NumPoints));
    Init(Start, End, NumPoints);
  }

  /// Useless constructor
  LinearGrid()
  { /*  Do nothing */
  }

  LinearGrid& operator=(const LinearGrid& lin)
  {
    grid.resize(lin.grid.shape());
    Start    = lin.Start;
    End      = lin.End;
    grid     = lin.grid;
    delta    = lin.delta;
    deltainv = lin.deltainv;
    return *this;
  }

  /// Constructor that sets the number of points, start and end point
  /// of the original grid
  LinearGrid(double start, double end, int numpoints) { Init(start, end, numpoints); }
};


/// General Grid inherets from Grid.
class GeneralGrid : public Grid
{
public:
  /// Returns the type of the grid (in this case GENERAL)
  GridType Type() override { return (GENERAL); }

  /// Returns the index of the nearest point below r.
  int ReverseMap(double r) override
  {
    if (r <= grid(0))
      return (0);
    else if (r >= grid(NumPoints - 1))
      return (NumPoints - 1);
    else
    {
      int hi    = NumPoints - 1;
      int lo    = 0;
      bool done = false;
      while (!done)
      {
        int i = (hi + lo) >> 1;
        if (grid(i) > r)
          hi = i;
        else
          lo = i;
        done = (hi - lo) < 2;
      }
      return std::min(lo, NumPoints - 2);
    }
  }

  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("General"));
  }

  void Read(IOSectionClass& inSection) override
  {
    assert(inSection.ReadVar("Points", grid));
    Start     = grid(0);
    End       = grid(grid.size() - 1);
    NumPoints = grid.size();
  }

  void Init(Array<double, 1>& points)
  {
    NumPoints = points.size();
    grid.resize(NumPoints);
    grid  = points;
    Start = grid(0);
    End   = grid(NumPoints - 1);
  }

  /// Useless constructor
  GeneralGrid()
  { /*  Do nothing */
  }
};


/// The OptimalGrid class stores a grid which has linear spacing at
/// the origin and exponential spacing further out.  It has the
/// analytic form \f[r_k = a\left(e^{kb}-1\right)\f].
class OptimalGrid : public Grid
{
private:
  double a, b;

public:
  GridType Type() override { return (OPTIMAL); }

  int ReverseMap(double r) override
  {
    if ((r / a) < 1e-6)
      return ((int)floor(r / (a * b) + 0.5) - 1);
    else
      return ((int)floor(log(r / a + 1.0) / b + 0.5) - 1);
  }

  /// Returns a parameter
  double Geta() const { return (a); }

  /// Returns b parameter
  double Getb() const { return (b); }

  OptimalGrid()
  {
    // Do nothing
  }

  /// This form of the constructor takes the number of points, the
  /// maximum radius and the value of b.
  void Init(int numpoints, double rmax, double bval)
  {
    NumPoints = numpoints;
    b         = bval;
    End       = rmax;
    a         = End / (exp(b * (double)NumPoints) - 1.0);
    Start     = a * (exp(b) - 1.0);
    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = a * (exp(b * (i + 1)) - 1.0);
  }

  OptimalGrid(int numPoints, double rmax, double bval) { Init(numPoints, rmax, bval); }

  void Init(double aval, double bval, int numPoints)
  {
    a         = aval;
    b         = bval;
    NumPoints = numPoints;
    Start     = a * (exp(b) - 1.0);
    End       = a * (exp(b * NumPoints) - 1.0);

    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = a * (exp(b * (i + 1)) - 1.0);
  }


  /// This form of the constructor takes a, b, and the number of points.
  OptimalGrid(double aval, double bval, int numPoints) { Init(aval, bval, numPoints); }

  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("Optimal"));
    outSection.WriteVar("a", a);
    outSection.WriteVar("b", b);
    outSection.WriteVar("NumPoints", NumPoints);
  }

  void Read(IOSectionClass& inSection) override
  {
    double aval, bval;
    int numPoints;
    if (inSection.ReadVar("a", aval))
    {
      assert(inSection.ReadVar("b", bval));
      assert(inSection.ReadVar("NumPoints", numPoints));
      Init(aval, bval, numPoints);
    }
    else
    {
      double Z, rmax;
      assert(inSection.ReadVar("Z", Z));
      assert(inSection.ReadVar("rmax", rmax));
      Init(Z, rmax);
    }
  }

  void InitRatio(double end, double ratio, int numpoints)
  {
    End       = end;
    NumPoints = numpoints;

    b = log(ratio) / (double)(numpoints - 2);
    a = end / (exp(b * (double)(numpoints - 1)) - 1);

    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = a * (exp(b * i) - 1.0);
  }


  /// This form of the constructor takes a nuclear charge and a
  /// maxmimum radius and chooses an appropriate number of points for
  /// that atom.
  void Init(double Z, double rmax)
  {
    a = 4.34e-6 / Z;
    //a = 4.0e-2;
    b = 0.002304;
    //b = 0.004;

    NumPoints = (int)ceil(log(rmax / a + 1.0) / b);
    b         = log(rmax / a + 1.0) / (double)NumPoints;
    Start     = a * (exp(b) - 1.0);
    End       = rmax;
    //End   = a * (exp(b*NumPoints) - 1.0);

    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
    {
      grid(i) = a * (exp(b * (i + 1)) - 1.0);
      //fprintf (stdout, "%1.12e\n", grid(i));
    }
  }

  inline OptimalGrid& operator=(const OptimalGrid& opt)
  {
    grid.resize(opt.grid.shape());
    a         = opt.a;
    b         = opt.b;
    NumPoints = opt.NumPoints;
    Start     = opt.Start;
    End       = opt.End;
    grid      = opt.grid;
    return *this;
  }

  OptimalGrid(double Z, double rmax) { Init(Z, rmax); }
};


/// The OptimalGrid class stores a grid which has linear spacing at
/// the origin and exponential spacing further out.  It has the
/// analytic form \f[r_k = a\left(e^{kb}-1\right)\f].
class OptimalGrid2 : public Grid
{
private:
  double a, b, c;
  double Ratio;

public:
  GridType Type() override { return (OPTIMAL2); }

  int ReverseMap(double r) override
  {
    //     if ((r/a) < 1e-6)
    //       return ((int)floor(r/(a*b)));
    //     else
    return ((int)floor(log1p((r - c) / a) / b));
  }

  /// Returns a parameter
  double Geta() const { return (a); }

  /// Returns b parameter
  double Getb() const { return (b); }

  OptimalGrid2()
  {
    // Do nothing
  }

  /// This form of the constructor takes the number of points, the
  /// maximum radius and the value of b.
  OptimalGrid2(int numpoints, double rmax, double bval)
  {
    NumPoints = numpoints;
    b         = bval;
    End       = rmax;
    a         = End / (exp(b * (double)NumPoints) - 1.0);
    Start     = a * (exp(b) - 1.0);
    grid.resize(NumPoints);
    c = 0.0;

    for (int i = 0; i < NumPoints; i++)
      grid(i) = c + a * expm1(b * i);
  }

  void Init(double start, double end, double ratio, int numpoints)
  {
    Start     = start;
    End       = end;
    Ratio     = ratio;
    NumPoints = numpoints;

    b = log(ratio) / (double)(numpoints - 2);
    c = Start;
    a = (end - c) / expm1(b * (double)(numpoints - 1));

    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = c + a * expm1(b * i);
  }


  /// This form of the constructor takes a, b, and the number of points.
  OptimalGrid2(double start, double end, double ratio, int numpoints) { Init(start, end, ratio, numpoints); }

  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("Optimal2"));
    outSection.WriteVar("Start", Start);
    outSection.WriteVar("End", End);
    outSection.WriteVar("Ratio", Ratio);
    outSection.WriteVar("NumPoints", NumPoints);
  }

  void Read(IOSectionClass& inSection) override
  {
    double start, end, ratio;
    int numPoints;
    assert(inSection.ReadVar("Start", start));
    assert(inSection.ReadVar("End", end));
    assert(inSection.ReadVar("Ratio", ratio));
    assert(inSection.ReadVar("NumPoints", numPoints));
    Init(start, end, ratio, numPoints);
  }
};


class CenterGrid : public Grid
{
private:
  double a, aInv, b, bInv, center;
  int HalfPoints;
  bool Odd;
  double EvenHalf;
  int OddOne;

public:
  // ratio gives approximately the largest grid spacing divided by the
  // smallest.
  GridType Type() override { return CENTER; }

  int ReverseMap(double x) override
  {
    x -= center;
    double index = copysign(log1p(std::abs(x) * aInv) * bInv, x);
    return (int)floor(HalfPoints + index - EvenHalf);
  }
  void Write(IOSectionClass& out) override {}
  void Read(IOSectionClass& in) override {}
  void Init(double start, double end, double ratio, int numPoints)
  {
    assert(ratio > 1.0);
    Start      = start;
    End        = end;
    center     = 0.5 * (start + end);
    NumPoints  = numPoints;
    HalfPoints = numPoints / 2;
    Odd        = ((numPoints % 2) == 1);
    b          = log(ratio) / (double)(HalfPoints - 1);
    bInv       = 1.0 / b;
    grid.resize(numPoints);
    if (Odd)
    {
      EvenHalf = 0.0;
      OddOne   = 1;
      a        = 0.5 * (end - start) / expm1(b * HalfPoints);
      aInv     = 1.0 / a;
      for (int i = -HalfPoints; i <= HalfPoints; i++)
      {
        double sign          = (i < 0) ? -1.0 : 1.0;
        grid(i + HalfPoints) = sign * a * expm1(b * std::abs(i)) + center;
      }
    }
    else
    {
      EvenHalf = 0.5;
      OddOne   = 0;
      a        = 0.5 * (end - start) / expm1(b * (-0.5 + HalfPoints));
      aInv     = 1.0 / a;
      for (int i = -HalfPoints; i < HalfPoints; i++)
      {
        double sign          = (i < 0) ? -1.0 : 1.0;
        grid(i + HalfPoints) = sign * a * expm1(b * std::abs(0.5 + i)) + center;
      }
    }
  }
};


/// LogGrid is a function whose gridpoints increase exponentially with
/// the index.  That is, it has the analytic form
/// \f[ r_k = \frac{r_0}{Z} \Delta^k.\f]  It is appropriate for
/// functions which change rapidly near the origin but vary smoothly
/// further out.
class LogGrid : public Grid
{
public:
  double Z, r0, Spacing;

  GridType Type() override { return (LOG); }

  int ReverseMap(double r) override { return ((int)(floor(log(Z * r / r0) / log(Spacing)))); }

  LogGrid()
  {
    // Do nothing
  }

  void Init(double R0, double spacing, int numpoints)
  {
    NumPoints = numpoints;
    Z         = 1.0;
    r0        = R0;
    Spacing   = spacing;
    Start     = r0;
    End       = r0 * pow(Spacing, (double)NumPoints - 1);
    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = r0 * pow(Spacing, (double)i);
  }


  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("Log"));
    outSection.WriteVar("r0", r0);
    outSection.WriteVar("Spacing", Spacing);
  }

  void Read(IOSectionClass& inSection) override
  {
    double tempr0, tempSpacing;
    int tempNumPoints;
    assert(inSection.ReadVar("r0", tempr0));
    assert(inSection.ReadVar("Spacing", tempSpacing));
    assert(inSection.ReadVar("NumPoints", tempNumPoints));
    Init(tempr0, tempSpacing, tempNumPoints);
  }

  LogGrid(double R0, double spacing, int numpoints) { Init(R0, spacing, numpoints); }

  LogGrid(int numpoints, double z, double R0, double spacing)
  {
    NumPoints = numpoints;
    Z         = z;
    r0        = R0;
    Spacing   = spacing;

    Start = r0 / Z;
    End   = r0 / Z * pow(Spacing, (double)(NumPoints - 1));

    grid.resize(NumPoints);

    for (int i = 0; i < NumPoints; i++)
      grid(i) = r0 / Z * pow(Spacing, (double)i);
  }
};


/// ClusterGrid is a function whose gridpoints are clustered tightly
/// around the origin.
class ClusterGrid : public Grid
{
private:
  double x0, dri, rr;

public:
  double Start, End, Cluster;

  GridType Type() override { return (CLUSTER); }

  int ReverseMap(double r) override { return ((int)floor(dri / (r - rr) - 1.0 + x0)); }

  void Init(double start, double end, double cluster, int numpoints)
  {
    Start     = start;
    End       = end;
    Cluster   = cluster;
    NumPoints = numpoints;

    x0  = (NumPoints - Cluster) / (1.0 - Cluster);
    dri = -(End - Start) * ((double)NumPoints - x0) * (1.0 - x0) / ((double)NumPoints - 1.0);
    rr  = Start - dri / (1.0 - x0);
    grid.resize(NumPoints);
    for (int i = 0; i < NumPoints; i++)
      grid(i) = rr + dri / (i + 1.0 - x0);
  }

  void Write(IOSectionClass& outSection) override
  {
    outSection.WriteVar("Points", grid);
    outSection.WriteVar("Type", std::string("Cluster"));
    outSection.WriteVar("Start", Start);
    outSection.WriteVar("End", End);
    outSection.WriteVar("Cluster", Cluster);
    outSection.WriteVar("NumPoints", NumPoints);
  }

  void Read(IOSectionClass& inSection) override
  {
    double start, end, cluster;
    int numpoints;
    assert(inSection.ReadVar("Start", start));
    assert(inSection.ReadVar("End", end));
    assert(inSection.ReadVar("Cluster", cluster));
    assert(inSection.ReadVar("NumPoints", numpoints));
    Init(start, end, cluster, numpoints);
  }

  ClusterGrid(double start, double end, double cluster, int numpoints) { Init(start, end, cluster, numpoints); }
  ClusterGrid()
  { /* Do nothing */
  }
};


inline std::shared_ptr<Grid> ReadGrid(IOSectionClass& inSection)
{
  std::string Type;
  assert(inSection.ReadVar("Type", Type));

  std::shared_ptr<Grid> newGrid;
  if (Type == "Linear")
    newGrid = std::make_shared<LinearGrid>();
  else if (Type == "General")
    newGrid = std::make_shared<GeneralGrid>();
  else if (Type == "Optimal")
    newGrid = std::make_shared<OptimalGrid>();
  else if (Type == "Optimal2")
    newGrid = std::make_shared<OptimalGrid2>();
  else if (Type == "Log")
    newGrid = std::make_shared<LogGrid>();
  else if (Type == "Cluster")
    newGrid = std::make_shared<ClusterGrid>();
  else
  {
    std::cerr << "Unrecognized Grid type " << Type << "\n";
    exit(1);
  }
  newGrid->Read(inSection);
  return newGrid;
}


inline void LinearGrid::CheckRoundingMode()
{
  for (int i = 0; i < 100; i++)
  {
    double x = 100.0 * drand48() - 50.0;
    if (nearbyint(x) != round(x))
    {
      std::cerr << "Error in rounding mode detected in LinearGrid.  Abort.\n";
      abort();
    }
  }
}


#endif