Add communication ring examples to solutions.ipynb

notebooks/solutions.ipynb

@@ -187,6 +187,110 @@
     "end"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "2f343157",
+   "metadata": {},
+   "source": [
+    "## Exercise: Ring communication - MPI"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "a49be691",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "using MPI\n",
+    "using Test\n",
+    "\n",
+    "MPI.Init()\n",
+    "comm = MPI.COMM_WORLD\n",
+    "rank = MPI.Comm_rank(comm)\n",
+    "id = rank + 1\n",
+    "root = 0\n",
+    "size = MPI.Comm_size(comm)\n",
+    "\n",
+    "dst = mod(rank + 1, size)\n",
+    "src = mod(rank - 1, size)\n",
+    "\n",
+    "send_buf = id\n",
+    "recv_buf = 1\n",
+    "\n",
+    "if rank == root \n",
+    "    # Proc 1: Send id async to destination, then wait for receive\n",
+    "    MPI.isend(send_buf, comm; dest=dst, tag=0)\n",
+    "    recv_buf = MPI.recv(comm; source=src, tag=0)\n",
+    "    @show recv_buf == factorial(size)\n",
+    "    @test recv_buf == factorial(size)\n",
+    "else\n",
+    "    # Other procs: receive sync and send async to next process\n",
+    "    recv_buf = MPI.recv(comm; source=src, tag=0)\n",
+    "    send_buf = recv_buf * id\n",
+    "    MPI.isend(send_buf, comm; dest=dst, tag=0)\n",
+    "end\n",
+    "\n",
+    "MPI.Finalize()"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "6cbbf074",
+   "metadata": {},
+   "source": [
+    "## Exercise: Ring communication - Distributed.jl"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "dc156523",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "using Distributed \n",
+    "using Test\n",
+    "\n",
+    "np = 4\n",
+    "add_n = np - nprocs() \n",
+    "addprocs(add_n)\n",
+    "worker_ids = workers()\n",
+    "@assert nprocs() > nworkers()\n",
+    "\n",
+    "# Initialize id channel\n",
+    "id_chnl = RemoteChannel(()->Channel{Int}(1))\n",
+    "put!(id_chnl, 1)\n",
+    "\n",
+    "# Initialize data channel\n",
+    "job_chnl = RemoteChannel(()->Channel{Int}(1))\n",
+    "put!(job_chnl, 1)\n",
+    "\n",
+    "@sync for w in workers()\n",
+    "    @spawnat w begin\n",
+    "        pos = findfirst(worker_ids .== w) + 1\n",
+    "        dst = mod(pos, np) + 1\n",
+    "        src = mod(pos-2, np) + 1\n",
+    "        while true \n",
+    "            pred = fetch(id_chnl)\n",
+    "            if pred == src\n",
+    "                take!(id_chnl)\n",
+    "                value = take!(job_chnl)\n",
+    "                put!(job_chnl, value * pos)  \n",
+    "                put!(id_chnl, pos)  \n",
+    "                break\n",
+    "            end\n",
+    "        end\n",
+    "    end\n",
+    "end\n",
+    "\n",
+    "res = take!(job_chnl)\n",
+    "@show res\n",
+    "@test res == factorial(np)\n",
+    "\n",
+    "rmprocs(workers())"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "47d88e7a",