simorthoprogram/simorthoprogram-orth_s_sar-.../linterp.h

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//
// Copyright (c) 2012 Ronaldo Carpio
//
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation. The authors make no representations
// about the suitability of this software for any purpose.
// It is provided "as is" without express or implied warranty.
//
/*
This is a C++ header-only library for N-dimensional linear interpolation on a rectangular grid. Implements two methods:
* Multilinear: Interpolate using the N-dimensional hypercube containing the point. Interpolation step is O(2^N)
* Simplicial: Interpolate using the N-dimensional simplex containing the point. Interpolation step is O(N log N), but less accurate.
Requires boost/multi_array library.
For a description of the algorithms, see:
* Weiser & Zarantonello (1988), "A Note on Piecewise Linear and Multilinear Table Interpolation in Many Dimensions", _Mathematics of Computation_ 50 (181), p. 189-196
* Davies (1996), "Multidimensional Triangulation and Interpolation for Reinforcement Learning", _Proceedings of Neural Information Processing Systems 1996_
*/
#ifndef _linterp_h
#define _linterp_h
#include <assert.h>
#include <math.h>
#include <stdarg.h>
#include <float.h>
#include <cstdarg>
#include <string>
#include <vector>
#include <array>
#include <functional>
#include <boost/multi_array.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/matrix_proxy.hpp>
#include <boost/numeric/ublas/storage.hpp>
using std::vector;
using std::array;
typedef unsigned int uint;
typedef vector<int> iVec;
typedef vector<double> dVec;
// TODO:
// - specify behavior past grid boundaries.
// 1) clamp
// 2) return a pre-determined value (e.g. NaN)
// compile-time params:
// 1) number of dimensions
// 2) scalar type T
// 3) copy data or not (default: false). The grids will always be copied
// 4) ref count class (default: none)
// 5) continuous or not
// run-time constructor params:
// 1) f
// 2) grids
// 3) behavior outside grid: default=clamp
// 4) value to return outside grid, defaut=nan
struct EmptyClass {};
template <int N, class T, bool CopyData = true, bool Continuous = true, class ArrayRefCountT = EmptyClass, class GridRefCountT = EmptyClass>
class NDInterpolator {
public:
typedef T value_type;
typedef ArrayRefCountT array_ref_count_type;
typedef GridRefCountT grid_ref_count_type;
static const int m_N = N;
static const bool m_bCopyData = CopyData;
static const bool m_bContinuous = Continuous;
typedef boost::numeric::ublas::array_adaptor<T> grid_type;
typedef boost::const_multi_array_ref<T, N> array_type;
typedef std::unique_ptr<array_type> array_type_ptr;
array_type_ptr m_pF;
ArrayRefCountT m_ref_F; // reference count for m_pF
vector<T> m_F_copy; // if CopyData == true, this holds the copy of F
vector<grid_type> m_grid_list;
vector<GridRefCountT> m_grid_ref_list; // reference counts for grids
vector<vector<T> > m_grid_copy_list; // if CopyData == true, this holds the copies of the grids
// constructors assume that [f_begin, f_end) is a contiguous array in C-order
// non ref-counted constructor.
template <class IterT1, class IterT2, class IterT3>
NDInterpolator(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end) {
init(grids_begin, grids_len_begin, f_begin, f_end);
}
// ref-counted constructor
template <class IterT1, class IterT2, class IterT3, class RefCountIterT>
NDInterpolator(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end, ArrayRefCountT &refF, RefCountIterT grid_refs_begin) {
init_refcount(grids_begin, grids_len_begin, f_begin, f_end, refF, grid_refs_begin);
}
template <class IterT1, class IterT2, class IterT3>
void init(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end) {
set_grids(grids_begin, grids_len_begin, m_bCopyData);
set_f_array(f_begin, f_end, m_bCopyData);
}
template <class IterT1, class IterT2, class IterT3, class RefCountIterT>
void init_refcount(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end, ArrayRefCountT &refF, RefCountIterT grid_refs_begin) {
set_grids(grids_begin, grids_len_begin, m_bCopyData);
set_grids_refcount(grid_refs_begin, grid_refs_begin + N);
set_f_array(f_begin, f_end, m_bCopyData);
set_f_refcount(refF);
}
template <class IterT1, class IterT2>
void set_grids(IterT1 grids_begin, IterT2 grids_len_begin, bool bCopy) {
m_grid_list.clear();
m_grid_ref_list.clear();
m_grid_copy_list.clear();
for (int i=0; i<N; i++) {
int gridLength = grids_len_begin[i];
if (bCopy == false) {
T const *grid_ptr = &(*grids_begin[i]);
m_grid_list.push_back(grid_type(gridLength, (T*) grid_ptr )); // use the given pointer
} else {
m_grid_copy_list.push_back( vector<T>(grids_begin[i], grids_begin[i] + grids_len_begin[i]) ); // make our own copy of the grid
T *begin = &(m_grid_copy_list[i][0]);
m_grid_list.push_back(grid_type(gridLength, begin)); // use our copy
}
}
}
template <class IterT1, class RefCountIterT>
void set_grids_refcount(RefCountIterT refs_begin, RefCountIterT refs_end) {
assert(refs_end - refs_begin == N);
m_grid_ref_list.assign(refs_begin, refs_begin + N);
}
// assumes that [f_begin, f_end) is a contiguous array in C-order
template <class IterT>
void set_f_array(IterT f_begin, IterT f_end, bool bCopy) {
unsigned int nGridPoints = 1;
array<int,N> sizes;
for (unsigned int i=0; i<m_grid_list.size(); i++) {
sizes[i] = m_grid_list[i].size();
nGridPoints *= sizes[i];
}
int f_len = f_end - f_begin;
if ( (m_bContinuous && f_len != nGridPoints) || (!m_bContinuous && f_len != 2 * nGridPoints) ) {
throw std::invalid_argument("f has wrong size");
}
for (unsigned int i=0; i<m_grid_list.size(); i++) {
if (!m_bContinuous) { sizes[i] *= 2; }
}
m_F_copy.clear();
if (bCopy == false) {
m_pF.reset(new array_type(f_begin, sizes));
} else {
m_F_copy = vector<T>(f_begin, f_end);
m_pF.reset(new array_type(&m_F_copy[0], sizes));
}
}
void set_f_refcount(ArrayRefCountT &refF) {
m_ref_F = refF;
}
// -1 is before the first grid point
// N-1 (where grid.size() == N) is after the last grid point
int find_cell(int dim, T x) const {
grid_type const &grid(m_grid_list[dim]);
if (x < *(grid.begin())) return -1;
else if (x >= *(grid.end()-1)) return grid.size()-1;
else {
auto i_upper = std::upper_bound(grid.begin(), grid.end(), x);
return i_upper - grid.begin() - 1;
}
}
// return the value of f at the given cell and vertex
T get_f_val(array<int,N> const &cell_index, array<int,N> const &v_index) const {
array<int,N> f_index;
if (m_bContinuous) {
for (int i=0; i<N; i++) {
if (cell_index[i] < 0) {
f_index[i] = 0;
} else if (cell_index[i] >= m_grid_list[i].size()-1) {
f_index[i] = m_grid_list[i].size()-1;
} else {
f_index[i] = cell_index[i] + v_index[i];
}
}
} else {
for (int i=0; i<N; i++) {
if (cell_index[i] < 0) {
f_index[i] = 0;
} else if (cell_index[i] >= m_grid_list[i].size()-1) {
f_index[i] = (2*m_grid_list[i].size())-1;
} else {
f_index[i] = 1 + (2*cell_index[i]) + v_index[i];
}
}
}
return (*m_pF)(f_index);
}
T get_f_val(array<int,N> const &cell_index, int v) const {
array<int,N> v_index;
for (int dim=0; dim<N; dim++) {
v_index[dim] = (v >> (N-dim-1)) & 1; // test if the i-th bit is set
}
return get_f_val(cell_index, v_index);
}
};
template <int N, class T, bool CopyData = true, bool Continuous = true, class ArrayRefCountT = EmptyClass, class GridRefCountT = EmptyClass>
class InterpSimplex : public NDInterpolator<N,T,CopyData,Continuous,ArrayRefCountT,GridRefCountT> {
public:
typedef NDInterpolator<N,T,CopyData,Continuous,ArrayRefCountT,GridRefCountT> super;
template <class IterT1, class IterT2, class IterT3>
InterpSimplex(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end)
: super(grids_begin, grids_len_begin, f_begin, f_end)
{}
template <class IterT1, class IterT2, class IterT3, class RefCountIterT>
InterpSimplex(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end, ArrayRefCountT &refF, RefCountIterT ref_begins)
: super(grids_begin, grids_len_begin, f_begin, f_end, refF, ref_begins)
{}
template <class IterT>
T interp(IterT x_begin) const {
array<T,1> result;
array< array<T,1>, N > coord_iter;
for (int i=0; i<N; i++) {
coord_iter[i][0] = x_begin[i];
}
interp_vec(1, coord_iter.begin(), coord_iter.end(), result.begin());
return result[0];
}
template <class IterT1, class IterT2>
void interp_vec(int n, IterT1 coord_iter_begin, IterT1 coord_iter_end, IterT2 i_result) const {
assert(N == coord_iter_end - coord_iter_begin);
array<int,N> cell_index, v_index;
array<std::pair<T, int>,N> xipair;
int c;
T y, v0, v1;
//mexPrintf("%d\n", n);
for (int i=0; i<n; i++) { // for each point
for (int dim=0; dim<N; dim++) {
typename super::grid_type const &grid(super::m_grid_list[dim]);
c = this->find_cell(dim, coord_iter_begin[dim][i]);
//mexPrintf("%d\n", c);
if (c == -1) { // before first grid point
y = 1.0;
} else if (c == grid.size()-1) { // after last grid point
y = 0.0;
} else {
//mexPrintf("%f %f\n", grid[c], grid[c+1]);
y = (coord_iter_begin[dim][i] - grid[c]) / (grid[c + 1] - grid[c]);
if (y < 0.0) y=0.0;
else if (y > 1.0) y=1.0;
}
xipair[dim].first = y;
xipair[dim].second = dim;
cell_index[dim] = c;
}
// sort xi's and get the permutation
std::sort(xipair.begin(), xipair.end(), [](std::pair<T, int> const &a, std::pair<T, int> const &b) {
return (a.first < b.first);
});
// walk the vertices of the simplex determined by the permutation
for (int j=0; j<N; j++) {
v_index[j] = 1;
}
v0 = this->get_f_val(cell_index, v_index);
y = v0;
for (int j=0; j<N; j++) {
v_index[xipair[j].second]--;
v1 = this->get_f_val(cell_index, v_index);
y += (1.0 - xipair[j].first) * (v1-v0); // interpolate
v0 = v1;
}
*i_result++ = y;
}
}
};
template <int N, class T, bool CopyData = true, bool Continuous = true, class ArrayRefCountT = EmptyClass, class GridRefCountT = EmptyClass>
class InterpMultilinear : public NDInterpolator<N,T,CopyData,Continuous,ArrayRefCountT,GridRefCountT> {
public:
typedef NDInterpolator<N,T,CopyData,Continuous,ArrayRefCountT,GridRefCountT> super;
template <class IterT1, class IterT2, class IterT3>
InterpMultilinear(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end)
: super(grids_begin, grids_len_begin, f_begin, f_end)
{}
template <class IterT1, class IterT2, class IterT3, class RefCountIterT>
InterpMultilinear(IterT1 grids_begin, IterT2 grids_len_begin, IterT3 f_begin, IterT3 f_end, ArrayRefCountT &refF, RefCountIterT ref_begins)
: super(grids_begin, grids_len_begin, f_begin, f_end, refF, ref_begins)
{}
template <class IterT1, class IterT2>
static T linterp_nd_unitcube(IterT1 f_begin, IterT1 f_end, IterT2 xi_begin, IterT2 xi_end) {
int n = xi_end - xi_begin;
int f_len = f_end - f_begin;
assert(1 << n == f_len);
T sub_lower, sub_upper;
if (n == 1) {
sub_lower = f_begin[0];
sub_upper = f_begin[1];
} else {
sub_lower = linterp_nd_unitcube(f_begin, f_begin + (f_len/2), xi_begin + 1, xi_end);
sub_upper = linterp_nd_unitcube(f_begin + (f_len/2), f_end, xi_begin + 1, xi_end);
}
T result = sub_lower + (*xi_begin)*(sub_upper - sub_lower);
return result;
}
template <class IterT>
T interp(IterT x_begin) const {
array<T,1> result;
array< array<T,1>, N > coord_iter;
for (int i=0; i<N; i++) {
coord_iter[i][0] = x_begin[i];
}
interp_vec(1, coord_iter.begin(), coord_iter.end(), result.begin());
return result[0];
}
template <class IterT1, class IterT2>
void interp_vec(int n, IterT1 coord_iter_begin, IterT1 coord_iter_end, IterT2 i_result) const {
assert(N == coord_iter_end - coord_iter_begin);
array<int,N> index;
int c;
T y, xi;
vector<T> f(1 << N);
array<T,N> x;
for (int i=0; i<n; i++) { // loop over each point
for (int dim=0; dim<N; dim++) { // loop over each dimension
auto const &grid(super::m_grid_list[dim]);
xi = coord_iter_begin[dim][i];
c = this->find_cell(dim, coord_iter_begin[dim][i]);
if (c == -1) { // before first grid point
y = 1.0;
} else if (c == grid.size()-1) { // after last grid point
y = 0.0;
} else {
y = (coord_iter_begin[dim][i] - grid[c]) / (grid[c + 1] - grid[c]);
if (y < 0.0) y=0.0;
else if (y > 1.0) y=1.0;
}
index[dim] = c;
x[dim] = y;
}
// copy f values at vertices
for (int v=0; v < (1 << N); v++) { // loop over each vertex of hypercube
f[v] = this->get_f_val(index, v);
}
*i_result++ = linterp_nd_unitcube(f.begin(), f.end(), x.begin(), x.end());
}
}
};
typedef InterpSimplex<1,double> NDInterpolator_1_S;
typedef InterpSimplex<2,double> NDInterpolator_2_S;
typedef InterpSimplex<3,double> NDInterpolator_3_S;
typedef InterpSimplex<4,double> NDInterpolator_4_S;
typedef InterpSimplex<5,double> NDInterpolator_5_S;
typedef InterpMultilinear<1,double> NDInterpolator_1_ML;
typedef InterpMultilinear<2,double> NDInterpolator_2_ML;
typedef InterpMultilinear<3,double> NDInterpolator_3_ML;
typedef InterpMultilinear<4,double> NDInterpolator_4_ML;
typedef InterpMultilinear<5,double> NDInterpolator_5_ML;
// C interface
extern "C" {
void linterp_simplex_1(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult);
void linterp_simplex_2(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult);
void linterp_simplex_3(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult);
}
void inline linterp_simplex_1(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult) {
const int N=1;
size_t total_size = 1;
for (int i=0; i<N; i++) {
total_size *= grid_len_begin[i];
}
InterpSimplex<N, double, false> interp_obj(grids_begin, grid_len_begin, pF, pF + total_size);
interp_obj.interp_vec(xi_len, xi_begin, xi_begin + N, pResult);
}
void inline linterp_simplex_2(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult) {
const int N=2;
size_t total_size = 1;
for (int i=0; i<N; i++) {
total_size *= grid_len_begin[i];
}
InterpSimplex<N, double, false> interp_obj(grids_begin, grid_len_begin, pF, pF + total_size);
interp_obj.interp_vec(xi_len, xi_begin, xi_begin + N, pResult);
}
void inline linterp_simplex_3(double **grids_begin, int *grid_len_begin, double *pF, int xi_len, double **xi_begin, double *pResult) {
const int N=3;
size_t total_size = 1;
for (int i=0; i<N; i++) {
total_size *= grid_len_begin[i];
}
InterpSimplex<N, double, false> interp_obj(grids_begin, grid_len_begin, pF, pF + total_size);
interp_obj.interp_vec(xi_len, xi_begin, xi_begin + N, pResult);
}
#endif //_linterp_h