/* SPDX-License-Identifier: BSD-2-Clause */ /* * Copyright (C) 2019, Raspberry Pi (Trading) Limited * * pwl.hpp - piecewise linear functions interface */ #pragma once #include <math.h> #include <vector> #include <boost/property_tree/ptree.hpp> namespace RPiController { class Pwl { public: struct Interval { Interval(double _start, double _end) : start(_start), end(_end) { } double start, end; bool Contains(double value) { return value >= start && value <= end; } double Clip(double value) { return value < start ? start : (value > end ? end : value); } double Len() const { return end - start; } }; struct Point { Point() : x(0), y(0) {} Point(double _x, double _y) : x(_x), y(_y) {} double x, y; Point operator-(Point const &p) const { return Point(x - p.x, y - p.y); } Point operator+(Point const &p) const { return Point(x + p.x, y + p.y); } double operator%(Point const &p) const { return x * p.x + y * p.y; } Point operator*(double f) const { return Point(x * f, y * f); } Point operator/(double f) const { return Point(x / f, y / f); } double Len2() const { return x * x + y * y; } double Len() const { return sqrt(Len2()); } }; Pwl() {} Pwl(std::vector<Point> const &points) : points_(points) {} void Read(boost::property_tree::ptree const ¶ms); void Append(double x, double y, const double eps = 1e-6); void Prepend(double x, double y, const double eps = 1e-6); Interval Domain() const; Interval Range() const; bool Empty() const; // Evaluate Pwl, optionally supplying an initial guess for the // "span". The "span" may be optionally be updated. If you want to know // the "span" value but don't have an initial guess you can set it to // -1. double Eval(double x, int *span_ptr = nullptr, bool update_span = true) const; // Find perpendicular closest to xy, starting from span+1 so you can // call it repeatedly to check for multiple closest points (set span to // -1 on the first call). Also returns "pseudo" perpendiculars; see // PerpType enum. enum class PerpType { None, // no perpendicular found Start, // start of Pwl is closest point End, // end of Pwl is closest point Vertex, // vertex of Pwl is closest point Perpendicular // true perpendicular found }; PerpType Invert(Point const &xy, Point &perp, int &span, const double eps = 1e-6) const; // Compute the inverse function. Indicate if it is a proper (true) // inverse, or only a best effort (e.g. input was non-monotonic). Pwl Inverse(bool *true_inverse = nullptr, const double eps = 1e-6) const; // Compose two Pwls together, doing "this" first and "other" after. Pwl Compose(Pwl const &other, const double eps = 1e-6) const; // Apply function to (x,y) values at every control point. void Map(std::function<void(double x, double y)> f) const; // Apply function to (x, y0, y1) values wherever either Pwl has a // control point. static void Map2(Pwl const &pwl0, Pwl const &pwl1, std::function<void(double x, double y0, double y1)> f); // Combine two Pwls, meaning we create a new Pwl where the y values are // given by running f wherever either has a knot. static Pwl Combine(Pwl const &pwl0, Pwl const &pwl1, std::function<double(double x, double y0, double y1)> f, const double eps = 1e-6); // Make "this" match (at least) the given domain. Any extension my be // clipped or linear. void MatchDomain(Interval const &domain, bool clip = true, const double eps = 1e-6); Pwl &operator*=(double d); void Debug(FILE *fp = stdout) const; private: int findSpan(double x, int span) const; std::vector<Point> points_; }; } // namespace RPiController