From 8e732627d258d2f46a4cec9f9e306b7f19abcd9e Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Tue, 10 Dec 2013 22:25:58 +0000
Subject: [PATCH] lolremez: add missing matrix.h implementation.

---
 tools/lolremez/matrix.h | 111 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 tools/lolremez/matrix.h

diff --git a/tools/lolremez/matrix.h b/tools/lolremez/matrix.h
new file mode 100644
index 00000000..e60bc1c7
--- /dev/null
+++ b/tools/lolremez/matrix.h
@@ -0,0 +1,111 @@
+//
+// LolRemez - Remez algorithm implementation
+//
+// Copyright: (c) 2010-2013 Sam Hocevar <sam@hocevar.net>
+//   This program is free software; you can redistribute it and/or
+//   modify it under the terms of the Do What The Fuck You Want To
+//   Public License, Version 2, as published by Sam Hocevar. See
+//   http://www.wtfpl.net/ for more details.
+//
+
+#pragma once
+
+using namespace lol;
+
+/*
+ * Arbitrarily-sized square matrices; for now this only supports
+ * naive inversion and is used for the Remez inversion method.
+ */
+
+template<typename T> struct Matrix
+{
+    inline Matrix<T>(int cols, int rows)
+      : m_cols(cols),
+        m_rows(rows)
+    {
+        ASSERT(cols > 0);
+        ASSERT(rows > 0);
+
+        m_data.Resize(m_cols * m_rows);
+    }
+
+    inline Matrix<T>(Matrix<T> const &other)
+    {
+        m_cols = other.m_cols;
+        m_rows = other.m_rows;
+        m_data = other.m_data;
+    }
+
+    void Init(T const &x)
+    {
+        for (int j = 0; j < m_rows; j++)
+            for (int i = 0; i < m_cols; i++)
+                m(i, j) = (i == j) ? x : (T)0;
+    }
+
+    /* Naive matrix inversion */
+    Matrix<T> inv() const
+    {
+        ASSERT(m_cols == m_rows);
+
+        Matrix a(*this), b(m_cols, m_rows);
+
+        b.Init((T)1);
+
+        /* Inversion method: iterate through all columns and make sure
+         * all the terms are 1 on the diagonal and 0 everywhere else */
+        for (int i = 0; i < m_cols; i++)
+        {
+            /* If the expected coefficient is zero, add one of
+             * the other lines. The first we meet will do. */
+            if (!a.m(i, i))
+            {
+                for (int j = i + 1; j < m_cols; j++)
+                {
+                    if (!a.m(i, j))
+                        continue;
+                    /* Add row j to row i */
+                    for (int n = 0; n < m_cols; n++)
+                    {
+                        a.m(n, i) += a.m(n, j);
+                        b.m(n, i) += b.m(n, j);
+                    }
+                    break;
+                }
+            }
+
+            /* Now we know the diagonal term is non-zero. Get its inverse
+             * and use that to nullify all other terms in the column */
+            T x = (T)1 / a.m(i, i);
+            for (int j = 0; j < m_cols; j++)
+            {
+                if (j == i)
+                    continue;
+                T mul = x * a.m(i, j);
+                for (int n = 0; n < m_cols; n++)
+                {
+                    a.m(n, j) -= mul * a.m(n, i);
+                    b.m(n, j) -= mul * b.m(n, i);
+                }
+            }
+
+            /* Finally, ensure the diagonal term is 1 */
+            for (int n = 0; n < m_cols; n++)
+            {
+                a.m(n, i) *= x;
+                b.m(n, i) *= x;
+            }
+        }
+
+        return b;
+    }
+
+    inline T & m(int i, int j) { return m_data[m_rows * j + i]; }
+    inline T const & m(int i, int j) const { return m_data[m_rows * j + i]; }
+
+    int m_cols, m_rows;
+
+private:
+    Array<T> m_data;
+};
+