compute_pi_1.ipynb

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   "source": [
    "import pycuda\n",
    "import pycuda.driver as cuda\n",
    "from pycuda.compiler import SourceModule\n",
    "import pycuda.autoinit\n",
    "import numpy as np\n",
    "import time"
   ]
  },
  {
   "cell_type": "code",
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   "id": "80c33611-eeb8-4820-bce2-b43d6a34d4ba",
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   "outputs": [],
   "source": [
    "def compute_pi_cpu(n_points):\n",
    "    x_rand = np.random.rand(n_points)\n",
    "    y_rand = np.random.rand(n_points)\n",
    "\n",
    "    n_inside = 0\n",
    "    for i in range(n_points):\n",
    "        n_inside += np.sqrt(x_rand[i]**2 + y_rand[i]**2) <= 1.0\n",
    "\n",
    "    pi = 4 * n_inside/n_points\n",
    "\n",
    "    return pi"
   ]
  },
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   "cell_type": "code",
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     "text": [
      "3.12890625\n",
      "Time to execute cpu version: 0.010859 seconds\n"
     ]
    }
   ],
   "source": [
    "tic = time.time()\n",
    "print(compute_pi_cpu(1024))\n",
    "toc = time.time()\n",
    "\n",
    "print(\"Time to execute cpu version: {:f} seconds\".format(toc-tic))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 72,
   "id": "aa19d57b-0bd0-4f18-998e-ec4a0a974b20",
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   "outputs": [],
   "source": [
    "pi_kernel_src = \"\"\"\n",
    "//Based on Stroustrup, adapted for CUDA\n",
    "//pseudorandom numbers\n",
    "__device__ float generateRandomNumber(long& last_draw) {\n",
    "    last_draw = last_draw*1103515245 + 12345;\n",
    "    long abs = last_draw & 0x7fffffff;\n",
    "    return abs / 2147483648.0; \n",
    "}\n",
    "\n",
    "__global__ void computePi(unsigned int* inside, unsigned int seed) {\n",
    "    //1 generate random numbers\n",
    "    unsigned int tid = threadIdx.x;\n",
    "    \n",
    "    long rand_seed = seed + tid;\n",
    "    float x = generateRandomNumber(rand_seed);\n",
    "    float y = generateRandomNumber(rand_seed);\n",
    "    \n",
    "    //2 compute the radius from the origin\n",
    "    float r = sqrt(x*x + y*y);\n",
    "    \n",
    "    //3 check if it is inside the circle\n",
    "    if (r <= 1.0) { // oh-oh\n",
    "        inside[tid] = 1;\n",
    "    }\n",
    "}\n",
    "\"\"\"\n",
    "\n",
    "mod = SourceModule(pi_kernel_src)\n",
    "func = mod.get_function(\"computePi\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 80,
   "id": "6291ac3a-64c9-414f-bec0-37284fb660bd",
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   "outputs": [],
   "source": [
    "def compute_pi_gpu(n_points):\n",
    "    bytes_per_uint = 4\n",
    "    \n",
    "    inside_gpu = cuda.mem_alloc(bytes_per_uint * n_points)\n",
    "    \n",
    "    func(inside_gpu, np.uint32(time.time()), block=(n_points,1,1), grid=(1,1,1))\n",
    "    \n",
    "    inside_cpu = np.empty(n_points, dtype=np.uint32)\n",
    "    cuda.memcpy_dtoh(inside_cpu, inside_gpu)\n",
    "    \n",
    "    n_inside = np.sum(inside_cpu)\n",
    "                \n",
    "    pi = 4 * n_inside/n_points\n",
    "            \n",
    "    return pi"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 81,
   "id": "0f895258-7fd0-4814-888d-97b36eec8426",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4.0\n",
      "Time to execute gpu version: 0.001571 seconds\n"
     ]
    }
   ],
   "source": [
    "tic = time.time()\n",
    "print(compute_pi_gpu(1024))\n",
    "toc = time.time()\n",
    "\n",
    "print(\"Time to execute gpu version: {:f} seconds\".format(toc-tic))"
   ]
  },
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   "cell_type": "code",
   "execution_count": null,
   "id": "989a6c31-045c-4791-94a7-e642b2102a1c",
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   "source": []
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