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 <vector> 24 25 #include <math.h> 26 27 // searchMax defines the upper limit on primes to find. 28 constexpr int searchMax = 10000000; 29 30 // searchChunkSize is the number of numbers searched, per task, for primes. 31 constexpr int searchChunkSize = 10000; 32 33 // isPrime returns true if i is prime. isPrime(int i)34bool isPrime(int i) { 35 auto c = static_cast<int>(sqrt(i)); 36 for (int j = 2; j <= c; j++) { 37 if (i % j == 0) { 38 return false; 39 } 40 } 41 return true; 42 } 43 main()44int main() { 45 // Create a marl scheduler using the full number of logical cpus. 46 // Bind this scheduler to the main thread so we can call marl::schedule() 47 marl::Scheduler scheduler(marl::Scheduler::Config::allCores()); 48 scheduler.bind(); 49 defer(scheduler.unbind()); // unbind before destructing the scheduler. 50 51 // Create a ticket queue. This will be used to ensure that the primes are 52 // printed in ascending order. 53 marl::Ticket::Queue queue; 54 55 // Iterate over the range [1, searchMax] in steps of searchChunkSize. 56 for (int searchBase = 1; searchBase <= searchMax; 57 searchBase += searchChunkSize) { 58 // Take a ticket from the ticket queue for this task. 59 auto ticket = queue.take(); 60 61 // Schedule the task. 62 marl::schedule([=] { 63 // Find all the primes in [searchBase, searchBase+searchChunkSize-1]. 64 // Note this is run in parallel with the other scheduled tasks. 65 std::vector<int> primes; 66 for (int i = searchBase; i < searchBase + searchChunkSize; i++) { 67 if (isPrime(i)) { 68 primes.push_back(i); 69 } 70 } 71 72 // Wait until the ticket is called. This ensures that the primes are 73 // printed in ascending order. This may cause this task to yield and allow 74 // other tasks to be executed while waiting for this ticket to be called. 75 ticket.wait(); 76 77 // Print the primes. 78 for (auto prime : primes) { 79 printf("%d is prime\n", prime); 80 } 81 82 // Call the next ticket so that those primes can be printed. 83 ticket.done(); 84 }); 85 } 86 87 // take a ticket and wait on it to ensure that all the primes have been 88 // calculated and printed. 89 queue.take().wait(); 90 91 return 0; 92 } 93