giordi91 · September 29, 2018 20:39 · Sep 29, 2018
diff --git a/bisect root finder b/bisect root finder
@@ -0,0 +1,85 @@
+#pragma once
+#include <limits>
+
+namespace cpp_tools {
+namespace numerical {
+
+template <typename T> using singleVariableFunction = float (*)(T xValue);
+struct ErrorReport {};
+
+template <typename T>
+inline bool ensureRangeSign(T startRange, T endRange,
+                            singleVariableFunction<T> function) {
+  T yStart = function(startRange);
+  T yEnd = function(endRange);
+  return (!((yStart > 0) & (yEnd > 0))) & (!((yStart < 0) & (yEnd < 0)));
+}
+
+template <typename T>
+inline bool rootValueMeetsAccuracyRequirements(T startRange, T endRange,
+                                               int accuracy) {
+  float denominator = powf(10.0f, accuracy);
+  float thresholdFloat = 1.0f / denominator;
+  return abs(endRange - startRange) < thresholdFloat;
+}
+
+template <typename T>
+inline T processFinalResultRounding(T startRange, T endRange,
+                                    singleVariableFunction<T> function,
+                                    ErrorReport *report) {
+  T midRange = (startRange + endRange) * 0.5f;
+
+  T midRangeFloor = (std::floorf(midRange*1000.0f)) / 1000.0f;
+  T midRangeCeil= (std::ceilf(midRange*1000.0f)) / 1000.0f;
+
+  T midRangeFloorCeil = (midRangeFloor+ midRangeCeil) * 0.5f;
+
+  bool lowSplit = ensureRangeSign(midRangeFloor, midRangeFloorCeil, function);
+  return lowSplit ? startRange : endRange;
+}
+
+template <typename T>
+T singleBisectRootFinder(T startRange, T endRange, singleVariableFunction<T> function,
+                   int accuracy, int maxIteration = 100,
+                   ErrorReport *errorReport = nullptr) {
+  const T nanValue = std::numeric_limits<T>::quiet_NaN();
+  if (!ensureRangeSign<T>(startRange, endRange, function)) {
+    return nanValue;
+  }
+
+  T midRange = (startRange + endRange) * 0.5f;
+  // lets start the iteration
+  T currentValue = function(midRange);
+
+  if (rootValueMeetsAccuracyRequirements(startRange, endRange, accuracy)) {
+    return processFinalResultRounding(startRange, endRange, function, errorReport);
+  }
+
+  bool lowSplit = ensureRangeSign(startRange, midRange, function);
+  bool highSplit = ensureRangeSign(midRange, endRange, function);
+  startRange = lowSplit ? startRange : midRange;
+  endRange = highSplit ? endRange : midRange;
+
+  int iteration = 1;
+  while (true & (iteration < maxIteration)) {
+
+    if (rootValueMeetsAccuracyRequirements(startRange, endRange, accuracy)) {
+      return processFinalResultRounding(startRange, endRange, function, errorReport);
+    }
+
+    midRange = (startRange + endRange) * 0.5f;
+    // lets start the iteration
+    currentValue = function(midRange);
+
+    bool lowSplit = ensureRangeSign(startRange, midRange, function);
+    bool highSplit = ensureRangeSign(midRange, endRange, function);
+    startRange = lowSplit ? startRange : midRange;
+    endRange = highSplit ? endRange : midRange;
+    iteration++;
+  }
+
+  T returnValue = midRange;
+  return returnValue;
+}
+} // namespace numerical
+} // namespace cpp_tools