1/*
2 * Copyright (c) 2015 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: David Guillen Fandos
38 */
39
40#ifndef __SIM_LINEAR_SOLVER_HH__
41#define __SIM_LINEAR_SOLVER_HH__
42
43#include <cassert>
44#include <sstream>
45#include <string>
46#include <vector>
47
48/**
49 * This class describes a linear equation with constant coefficients.
50 * The equation has a certain (variable) number of unkowns and it can hold
51 * N+1 coefficients.
52 */
53
54class LinearEquation {
55  public:
56    LinearEquation(unsigned unknowns) {
57        eq = std::vector <double> (unknowns + 1, 0);
58    }
59
60    // Add two equations
61    LinearEquation operator+ (const LinearEquation& rhs) {
62        assert(this->eq.size() == rhs.eq.size());
63
64        LinearEquation res(this->eq.size() - 1);
65
66        for (unsigned i = 0; i < res.eq.size(); i++)
67            res.eq[i] = this->eq[i] + rhs.eq[i];
68
69        return res;
70    }
71
72    // Multiply the equation by a constant
73    LinearEquation & operator*= (const double cnt) {
74        for (auto & c: eq)
75            c *= cnt;
76
77        return *this;
78    }
79
80    // Access a certain equation coefficient
81    double & operator[] (unsigned unkw) {
82        assert(unkw < eq.size());
83        return eq[unkw];
84    }
85
86    // Get a string representation
87    std::string toStr() const {
88        std::ostringstream oss;
89        for (unsigned i = 0; i < eq.size(); i++) {
90            if (i)
91                oss << " + ";
92            oss << eq[i];
93            if (i != eq.size() - 1)
94                oss << "*x" << i;
95        }
96        oss << " = 0";
97        return oss.str();
98    }
99
100    // Index for the constant term
101    unsigned cnt() const { return eq.size() - 1; }
102
103  private:
104
105    /** Coefficients */
106    std::vector <double> eq;
107};
108
109class LinearSystem {
110  public:
111    LinearSystem(unsigned unknowns) {
112        for (unsigned i = 0; i < unknowns; i++)
113            matrix.push_back(LinearEquation(unknowns));
114    }
115
116    LinearEquation & operator[] (unsigned eq) {
117        assert(eq < matrix.size());
118        return matrix[eq];
119    }
120
121    std::string toStr() const {
122        std::string r;
123        for (auto & eq: matrix)
124            r += eq.toStr() + "\n";
125        return r;
126    }
127
128    std::vector <double> solve() const;
129
130  private:
131    std::vector < LinearEquation > matrix;
132};
133
134#endif
135