1 // Copyright 2019 The Marl Authors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 // This is an example application that uses Marl to find and print all the prime 16 // numbers in the range 1 to 10000000. 17 18 #include "marl/defer.h" 19 #include "marl/scheduler.h" 20 #include "marl/thread.h" 21 #include "marl/ticket.h" 22 23 #include <math.h> 24 25 // searchMax defines the upper limit on primes to find. 26 constexpr int searchMax = 10000000; 27 28 // searchChunkSize is the number of numbers searched, per task, for primes. 29 constexpr int searchChunkSize = 10000; 30 31 // isPrime returns true if i is prime. isPrime(int i)32bool isPrime(int i) { 33 auto c = static_cast<int>(sqrt(i)); 34 for (int j = 2; j <= c; j++) { 35 if (i % j == 0) { 36 return false; 37 } 38 } 39 return true; 40 } 41 main()42int main() { 43 // Create a marl scheduler using the full number of logical cpus. 44 // Bind this scheduler to the main thread so we can call marl::schedule() 45 marl::Scheduler scheduler; 46 scheduler.setWorkerThreadCount(marl::Thread::numLogicalCPUs()); 47 scheduler.bind(); 48 defer(scheduler.unbind()); // unbind before destructing the scheduler. 49 50 // Create a ticket queue. This will be used to ensure that the primes are 51 // printed in ascending order. 52 marl::Ticket::Queue queue; 53 54 // Iterate over the range [1, searchMax] in steps of searchChunkSize. 55 for (int searchBase = 1; searchBase <= searchMax; 56 searchBase += searchChunkSize) { 57 // Take a ticket from the ticket queue for this task. 58 auto ticket = queue.take(); 59 60 // Schedule the task. 61 marl::schedule([=] { 62 // Find all the primes in [searchBase, searchBase+searchChunkSize-1]. 63 // Note this is run in parallel with the other scheduled tasks. 64 std::vector<int> primes; 65 for (int i = searchBase; i < searchBase + searchChunkSize; i++) { 66 if (isPrime(i)) { 67 primes.push_back(i); 68 } 69 } 70 71 // Wait until the ticket is called. This ensures that the primes are 72 // printed in ascending order. This may cause this task to yield and allow 73 // other tasks to be executed while waiting for this ticket to be called. 74 ticket.wait(); 75 76 // Print the primes. 77 for (auto prime : primes) { 78 printf("%d is prime\n", prime); 79 } 80 81 // Call the next ticket so that those primes can be printed. 82 ticket.done(); 83 }); 84 } 85 86 // take a ticket and wait on it to ensure that all the primes have been 87 // calculated and printed. 88 queue.take().wait(); 89 90 return 0; 91 } 92