Compute Fibonacci numbers concurrently

Overview

In this example, we will demonstrate how to use the objects and the APIs defined in wasmedge-sys to compute Fibonacci numbers concurrently. we creates two child threads, thread_a and thread_b, which are responsible 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.

The code in the example is verified on

• wasmedge-sys v0.10.0
• wasmedge-types v0.3.0

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

#![allow(unused)]
fn main() {
// create a Config context
let mut config = Config::create()?;
config.bulk_memory_operations(true);

// create a Store context
let mut store = Store::create()?;

// create a Vm context with the given Config and Store
let mut vm = Vm::create(Some(config), Some(&mut store))?;

// register a wasm module from a wasm file
let file = std::path::PathBuf::from(env!("WASMEDGE_DIR"))
    .join("bindings/rust/wasmedge-sys/tests/data/fibonacci.wasm");
vm.register_wasm_from_file("extern", file)?;

}

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

#![allow(unused)]
fn main() {
let vm = Arc::new(Mutex::new(vm));

// compute fib(4) by a child thread
let vm_cloned = Arc::clone(&vm);
let handle_a = thread::spawn(move || {
    let vm_child_thread = vm_cloned.lock().expect("fail to lock vm");
    let returns = vm_child_thread
        .run_registered_function("extern", "fib", [WasmValue::from_i32(4)])
        .expect("fail to compute fib(4)");

    let fib4 = returns[0].to_i32();
    println!("fib(4) by child thread: {}", fib4);

    fib4
});

// compute fib(5) by a child thread
let vm_cloned = Arc::clone(&vm);
let handle_b = thread::spawn(move || {
    let vm_child_thread = vm_cloned.lock().expect("fail to lock vm");
    let returns = vm_child_thread
        .run_registered_function("extern", "fib", [WasmValue::from_i32(5)])
        .expect("fail to compute fib(5)");

    let fib5 = returns[0].to_i32();
    println!("fib(5) by child thread: {}", fib5);

    fib5
});

}

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 in threads.rs.