Every function you define in Clio, has a parallel, distributed version. This parallel version can be accessed using the sandwich syntax. Let’s start by an example and define a fibonacci function:


Running the following example in the playground might freeze your browser for a few seconds!

In the above example, we are running fib function on all the members of our array. The code above, first runs fib 39, and when the result is ready it will run the next, which is fib 40 and so on. If I run the above code on my laptop, it will take about 6.2 seconds to finish. However, we can make the above code faster, by running all the fibs in parallel, and at the same time. To do this, we will use the parallel version of our fib function, which can be accessed using the sandwich syntax:


Unlike the previous example, this one won’t freeze your browser!


Parallel functions are async, you need to await them if necessary.

This time, if I run the above code it will take 2.7 seconds instead. Much faster, isn’t it? You might wonder, if we are running in 4 processes instead of one, why isn’t it 4 times faster? That’s a very good question, and here’s the answer: We’re limited by the performance of the longest running process, if you wait for 4 processes where 3 of them run in 1 second and one of them runs in 10 seconds, your overall wait time is going to be 10 seconds.


Being faster isn’t the only benefit of running functions in parallel. On the browser, the regular non-parallel fib blocks the ui, but the parallel version doesn’t. If you try the above examples in the playground you will see this in action.

Alternatively, you can use the .then method for handling parallel tasks: