Define constructors for state.hpp explicitly

Our threads need to negotiate access and mutation to the two
resources - we don't want them treading on each others toes when
generating new child nodes /or/ when trying to remove/add work to the
queue.  The former situation is particularly worrisome due to how weak
the indexing system is with the allocator.

build.sh

@@ -7,4 +7,4 @@ DFLAGS="-ggdb -fsanitize=address -fsanitize=undefined"
 CFLAGS="$GFLAGS $DFLAGS"
 LIBS="-lraylib -lm"
 
-c++ $CFLAGS -o cw_tree.out src/numerics.cpp src/main.cpp $LIBS
+c++ $CFLAGS -o cw_tree.out src/node.cpp src/state.cpp src/worker.cpp src/numerics.cpp src/main.cpp $LIBS

src/base.hpp

@@ -0,0 +1,57 @@
+/* base.hpp: Basic definitions
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef BASE_HPP
+#define BASE_HPP
+
+#include <cassert>
+#include <cstdint>
+#include <optional>
+
+#define MIN(A, B) ((A) < (B) ? (A) : (B))
+#define MAX(A, B) ((B) < (A) ? (A) : (B))
+
+using u8  = uint8_t;
+using u16 = uint16_t;
+using u32 = uint32_t;
+using u64 = uint64_t;
+
+using i8  = int8_t;
+using i16 = int16_t;
+using i32 = int32_t;
+using i64 = int64_t;
+
+static_assert(sizeof(float) == 4, "f32 requires 4 byte floats");
+static_assert(sizeof(double) == 8, "f64 requires 8 byte doubles");
+using f32 = float;
+using f64 = double;
+
+inline u64 gcd(u64 a, u64 b)
+{
+  if (a == b)
+    return a;
+  else if (a <= 1 || b <= 1)
+    return 1;
+  for (u64 r = b % a; r != 0; b = a, a = r, r = b % a)
+    continue;
+  return a;
+}
+
+#endif
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/node.cpp

@@ -0,0 +1,133 @@
+/* node.cpp: Implementations of various functions for fractions and nodes
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include <sstream>
+
+#include "node.hpp"
+
+namespace cw::node
+{
+  /**************************************/
+  /*  ___            _   _              */
+  /* | __| _ __ _ __| |_(_)___ _ _  ___ */
+  /* | _| '_/ _` / _|  _| / _ \ ' \(_-< */
+  /* |_||_| \__,_\__|\__|_\___/_||_/__/ */
+  /*                                    */
+  /**************************************/
+  Fraction::Fraction(u64 numerator, u64 denominator)
+      : numerator{numerator}, denominator{denominator},
+        norm{numerator / ((f64)denominator)}
+  {
+    u64 hcf = gcd(MIN(numerator, denominator), MAX(numerator, denominator));
+    numerator /= hcf;
+    denominator /= hcf;
+  }
+
+  bool Fraction::operator<(const Fraction other)
+  {
+    if (other.denominator == denominator)
+      return numerator < other.numerator;
+    return (numerator * other.denominator) < (other.numerator * denominator);
+  }
+
+  bool Fraction::operator==(const Fraction &other)
+  {
+    return numerator == other.numerator && denominator == other.denominator;
+  }
+
+  std::string to_string(const Fraction &f)
+  {
+    std::stringstream ss;
+    ss << f.numerator << "/" << f.denominator;
+    return ss.str();
+  }
+
+  /***************************/
+  /*  _  _         _         */
+  /* | \| |___  __| |___ ___ */
+  /* | .` / _ \/ _` / -_|_-< */
+  /* |_|\_\___/\__,_\___/__/ */
+  /*                         */
+  /***************************/
+  Node::Node(const Fraction &&val, i64 left, i64 right)
+      : value{val}, left{left}, right{right}
+  {
+  }
+
+  NodeAllocator::NodeAllocator(u64 capacity)
+  {
+    vec.reserve(capacity);
+  }
+
+  u64 NodeAllocator::alloc(Node n)
+  {
+    u64 ind = vec.size();
+    vec.push_back(n);
+    return ind;
+  }
+
+  // FIXME: This is annoying.  DRY?
+  Node &NodeAllocator::get_ref(u64 n)
+  {
+    if (n >= vec.size())
+      return vec[0];
+    return vec[n];
+  }
+
+  Node NodeAllocator::get_val(u64 n) const
+  {
+    if (n >= vec.size())
+      return vec[0];
+    return vec[n];
+  }
+
+  void indent_depth(int depth, std::stringstream &ss)
+  {
+    for (int i = 0; i < depth; ++i)
+      ss << "  ";
+  }
+
+  std::string to_string(const NodeAllocator &allocator, const i64 n, int depth)
+  {
+    if (n < 0)
+      return "NIL";
+
+    std::stringstream ss;
+    Node x = allocator.get_val(n);
+    ss << "(" << to_string(x.value) << "\n";
+
+    indent_depth(depth, ss);
+    if (x.left == -1)
+      ss << "NIL";
+    else
+      ss << to_string(allocator, x.left, depth + 1);
+    ss << "\n";
+
+    indent_depth(depth, ss);
+    if (x.right == -1)
+      ss << "NIL";
+    else
+      ss << to_string(allocator, x.right, depth + 1);
+
+    ss << ")";
+    return ss.str();
+  }
+
+} // namespace cw::node
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/node.hpp

@@ -0,0 +1,66 @@
+/* node.hpp: Definition of fractions and nodes on the Calkin-Wilf tree
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef NODE_HPP
+#define NODE_HPP
+
+#include <string>
+#include <vector>
+
+#include "base.hpp"
+
+namespace cw::node
+{
+  struct Fraction
+  {
+    u64 numerator, denominator; // always simplified
+    f64 norm;
+
+    Fraction(u64 numerator = 0, u64 denominator = 1);
+
+    // Complete ordering on Fractions
+    bool operator<(const Fraction other);
+    bool operator==(const Fraction &other);
+  };
+
+  std::string to_string(const Fraction &);
+
+  struct Node
+  {
+    Fraction value;
+    i64 left, right;
+
+    Node(const Fraction &&val = {}, i64 left = -1, i64 right = -1);
+  };
+
+  struct NodeAllocator
+  {
+    std::vector<Node> vec;
+
+    NodeAllocator(u64 capacity = 256);
+    u64 alloc(Node n);
+    Node get_val(u64 n) const;
+    Node &get_ref(u64 n);
+  };
+
+  std::string to_string(const NodeAllocator &, const i64, int depth = 1);
+} // namespace cw::node
+
+#endif
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/state.cpp

@@ -0,0 +1,39 @@
+/* state.cpp:
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include "state.hpp"
+#include <cmath>
+
+namespace cw::state
+{
+  void DrawState::compute_bounds()
+  {
+    bounds.leftmost = state.allocator.get_val(0);
+    while (bounds.leftmost.left >= 0)
+      bounds.leftmost = state.allocator.get_val(bounds.leftmost.left);
+
+    bounds.rightmost = state.allocator.get_val(0);
+    while (bounds.rightmost.right >= 0)
+      bounds.rightmost = state.allocator.get_val(bounds.rightmost.right);
+
+    bounds.lower_val = std::floorl(bounds.leftmost.value.norm);
+    bounds.upper_val = std::ceill(bounds.rightmost.value.norm);
+  }
+} // namespace cw::state
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/state.hpp

@@ -0,0 +1,58 @@
+/* state.hpp: General state of the simulation
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef STATE_HPP
+#define STATE_HPP
+
+#include <mutex>
+#include <queue>
+
+#include "base.hpp"
+#include "node.hpp"
+
+namespace cw::state
+{
+  struct State
+  {
+    cw::node::NodeAllocator allocator;
+    std::queue<u64> queue;
+
+    std::mutex mutex_queue;
+    std::mutex mutex_allocator;
+
+    State(void) {};
+  };
+
+  struct DrawState
+  {
+    const State &state;
+    struct Bounds
+    {
+      cw::node::Node leftmost, rightmost;
+      f64 lower_val, upper_val;
+    } bounds;
+
+    DrawState(const State &state) : state{state} {};
+
+    void compute_bounds(void);
+  };
+} // namespace cw::state
+
+#endif
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/worker.cpp

@@ -0,0 +1,70 @@
+/* worker.cpp: Implementation of workers in our simulation
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#include "worker.hpp"
+#include <tuple>
+
+namespace cw::worker
+{
+  using cw::node::Fraction;
+  using cw::node::Node;
+
+  std::tuple<u64, u64> generate_children(NodeAllocator &allocator, u64 index)
+  {
+    Node node = allocator.get_val(index);
+    if (node.left < 0)
+    {
+      allocator.get_ref(index).left = allocator.alloc(Fraction{
+          node.value.numerator, node.value.numerator + node.value.denominator});
+    }
+    if (node.right < 0)
+    {
+      allocator.get_ref(index).right = allocator.alloc(
+          Fraction{node.value.numerator + node.value.denominator,
+                   node.value.denominator});
+    }
+    return {node.left, node.right};
+  }
+
+  void do_iteration(State &state)
+  {
+    state.mutex_queue.lock();
+    if (state.queue.empty())
+    {
+      // Unlock since there isn't any work to be done.
+      state.mutex_queue.unlock();
+      return;
+    }
+    u64 index = state.queue.front();
+    state.queue.pop();
+    state.mutex_queue.unlock();
+
+    u64 left_child, right_child;
+    state.mutex_allocator.lock();
+    std::tie(left_child, right_child) =
+        generate_children(state.allocator, index);
+    state.mutex_allocator.unlock();
+
+    state.mutex_queue.lock();
+    state.queue.push(left_child);
+    state.queue.push(right_child);
+    state.mutex_queue.unlock();
+  }
+} // namespace cw::worker
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */

src/worker.hpp

@@ -0,0 +1,46 @@
+/* worker.hpp: Definition of "workers" who will generate nodes on the tree
+ * Created: 2025-11-27
+ * Author: Aryadev Chavali
+ * License: See end of file
+ * Commentary:
+ */
+
+#ifndef WORKER_HPP
+#define WORKER_HPP
+
+#include <tuple>
+
+#include "state.hpp"
+
+namespace cw::worker
+{
+  using cw::node::NodeAllocator;
+  using cw::state::State;
+
+  // Given `index`, return the indices of its children in the tree.  If not
+  // present already, generate them using the allocator.
+  std::tuple<u64, u64> generate_children(NodeAllocator &allocator, u64 index);
+
+  // Performs a single iteration which consists of the following:
+  // 1) pop an index off the iteration queue
+  // 2) generate the children of the node at that index
+  // 3) push the indices of the children onto the iteration queue
+  // Each step will block on the relevant mutex for the resource (1,3 will block
+  // on the queue mutex, 2 will block on the allocator mutex) so is thread safe.
+  void do_iteration(State &state);
+} // namespace cw::worker
+
+#endif
+
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License Version 2 for
+ * details.
+
+ * You may distribute and modify this code under the terms of the GNU General
+ * Public License Version 2, which you should have received a copy of along with
+ * this program.  If not, please go to <https://www.gnu.org/licenses/>.
+
+ */