readers_writers.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import threading\n",
    "import time"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "class ReadWriteLock:\n",
    "    def __init__(self):\n",
    "        self.readers_count = 0\n",
    "        self.writers_count = 0\n",
    "        self.readers_count_lock = threading.Lock()\n",
    "        self.resource_lock = threading.Lock()\n",
    "\n",
    "    def acquire_read(self):\n",
    "        with self.readers_count_lock:\n",
    "            self.readers_count += 1\n",
    "            if self.readers_count == 1:\n",
    "                self.resource_lock.acquire()\n",
    "\n",
    "    def release_read(self):\n",
    "        with self.readers_count_lock:\n",
    "            self.readers_count -= 1\n",
    "            if self.readers_count == 0:\n",
    "                self.resource_lock.release()\n",
    "\n",
    "    def acquire_write(self):\n",
    "        with self.resource_lock:\n",
    "            self.writers_count += 1\n",
    "            while self.readers_count > 0:\n",
    "                # Wait for all readers to finish\n",
    "                pass\n",
    "\n",
    "    def release_write(self):\n",
    "        with self.resource_lock:\n",
    "            self.writers_count -= 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Timer function\n",
    "def stop_all_processes(lock, threads):\n",
    "    print(\"Timer expired. Stopping all processes.\")\n",
    "    \n",
    "    # Release any locks to allow threads to exit gracefully\n",
    "    lock.release_read()\n",
    "    lock.release_write()\n",
    "\n",
    "    # Interrupt all threads to stop them\n",
    "    for thread in threads:\n",
    "        thread.join(timeout=0.1)  # Wait for the thread to finish\n",
    "        raise SystemExit(0)  # Interrupt the thread"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "def reader(lock, reader_id):\n",
    "    while True:\n",
    "        time.sleep(1)  # Simulate reading\n",
    "        lock.acquire_read()\n",
    "        print(f\"Reader {reader_id} is reading.\")\n",
    "        lock.release_read()\n",
    "\n",
    "def writer(lock, writer_id, stopp_event):\n",
    "    while True:\n",
    "        # global stopp_event\n",
    "        if stopp_event <= 0:\n",
    "            break\n",
    "        time.sleep(2)  # Simulate writing\n",
    "        lock.acquire_write()\n",
    "        print(f\"Writer {writer_id} is writing.\")\n",
    "        lock.release_write()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "\n",
      "Writer 0 is writing.\n",
      "Timer expired. Stopping all processes.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n"
     ]
    },
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.Reader 1 is reading.\n",
      "\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 1 is writing.Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Reader 2 is reading.\n",
      "\n",
      "Reader 1 is reading.Reader 0 is reading.\n",
      "\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Reader 0 is reading.\n",
      "Writer 1 is writing.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 1 is reading.Reader 2 is reading.\n",
      "\n",
      "Reader 0 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.\n",
      "Writer 1 is writing.\n",
      "Reader 2 is reading.\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 0 is reading.Reader 2 is reading.\n",
      "\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.Writer 1 is writing.\n",
      "\n",
      "Reader 0 is reading.\n",
      "Reader 2 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.Reader 0 is reading.\n",
      "\n",
      "Reader 1 is reading.\n",
      "Writer 0 is writing.Writer 1 is writing.\n",
      "\n",
      "Reader 0 is reading.\n",
      "Reader 1 is reading.\n",
      "Reader 2 is reading.\n"
     ]
    }
   ],
   "source": [
    "# Example usage:      \n",
    "\n",
    "if __name__ == \"__main__\":\n",
    "    stopp_event = 5\n",
    "    rw_lock = ReadWriteLock()\n",
    "\n",
    "    # Create reader and writer threads\n",
    "    readers = [threading.Thread(target=reader, args=(rw_lock, i)) for i in range(3)]\n",
    "    writers = [threading.Thread(target=writer, args=(rw_lock, i, stopp_event)) for i in range(2)]\n",
    "\n",
    "    # Start threads\n",
    "    for r in readers:\n",
    "        r.start()\n",
    "\n",
    "    for w in writers:\n",
    "        w.start()\n",
    "\n",
    "    # Set up a timer to stop all processes after a specified duration\n",
    "    timer_duration = 4  # seconds\n",
    "    timer = threading.Timer(timer_duration, stop_all_processes, args=(rw_lock, readers + writers))\n",
    "    timer.start()\n",
    "\n",
    "    # Wait for the timer to expire\n",
    "    timer.join()"
   ]
  }
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