Compute Fibonacci numbers concurrently

Prerequisites

This example uses the following crates:

  • wasmedge-sys v0.7.0
  • wasmedge-types v0.1.1

Overview

In this example, we will demonstrate how to use the objects and the APIs defined in wasmedge-sys to compute Fibonacci numbers concurrently.

Example

In the following code, we creates two child threads, thread_a and thread_b, which are responsbile for compute Fib(4) and Fib(5) by calling the host function fib, respectively. After that, the main thread computes Fib(6) by adding the numbers returned by thread_a and thread_b.

Step 1: create a Vm context and register the WebAssembly module

  2. #![allow(unused)]
  3. fn main() {
  4. // create a Config context
  5. let mut config = Config::create()?;
  6. config.bulk_memory_operations(true);
  8. // create a Store context
  9. let mut store = Store::create()?;
  11. // create a Vm context with the given Config and Store
  12. let mut vm = Vm::create(Some(config), Some(&mut store))?;
  14. // register a wasm module from a wasm file
  15. let file = std::path::PathBuf::from(env!("WASMEDGE_DIR"))
  16.     .join("bindings/rust/wasmedge-sys/tests/data/fibonacci.wasm");
  17. vm.register_wasm_from_file("extern", file)?;
  18. }

Step 2: create two child threads to compute Fib(4) and Fib(5) respectively

  2. #![allow(unused)]
  3. fn main() {
  4. let vm = Arc::new(Mutex::new(vm));
  6. // compute fib(4) by a child thread
  7. let vm_cloned = Arc::clone(&vm);
  8. let handle_a = thread::spawn(move || {
  9.   let vm_child_thread = vm_cloned.lock().expect("fail to lock vm");
  10.   let returns = vm_child_thread
  11.     .run_registered_function("extern", "fib", [WasmValue::from_i32(4)])
  12.     .expect("fail to compute fib(4)");
  14.   let fib4 = returns[0].to_i32();
  15.   println!("fib(4) by child thread: {}", fib4);
  17.   fib4
  18. });
  20. // compute fib(5) by a child thread
  21. let vm_cloned = Arc::clone(&vm);
  22. let handle_b = thread::spawn(move || {
  23.   let vm_child_thread = vm_cloned.lock().expect("fail to lock vm");
  24.   let returns = vm_child_thread
  25.     .run_registered_function("extern", "fib", [WasmValue::from_i32(5)])
  26.     .expect("fail to compute fib(5)");
  28.   let fib5 = returns[0].to_i32();
  29.   println!("fib(5) by child thread: {}", fib5);
  31.   fib5
  32. });
  34. }

Step3: Get the returns from the two child threads, and compute Fib(6)

let fib4 = handle_a.join().unwrap(); let fib5 = handle_b.join().unwrap(); // compute fib(6) println!("fib(6) = fib(5) + fib(1) = {}", fib5 + fib4);

The final result of the code above should be printed on the screen like below:

fib(4) by child thread: 5 fib(5) by child thread: 8 fib(6) = fib(5) + fib(1) = 13

The complete code in this demo can be found on WasmEdge Github.