Feature request: automatic warmup

[colinhacks]

It seems a little odd that you must call .warmup() even if you've already specified warmup* options when initializing the benchmark. I respect the choice to make warmups explicit, but I think there may be an API that accomplishes both.

The idea is to add a warmup key to Options that can accept boolean | { time?: number; iterations?: number }. If this key is specified & truthy, the benchmark will automatically call .warmup() when run.

const a = new Bench({ warmup: true }); // auto-warmup, default config
const b = new Bench({ warmup: { time: 400 }}); // auto-warmup, warmupTime=400
const b = new Bench({ warmup: { iterations: 1000 }}); // auto-warmup, iterations=400

This is a non-breaking change since it's a brand new option. Users opt into the "auto warmup" feature by specifying warmup. The existing keys warmupTime and warmupIterations can continue to be supported though you'd presumably throw an informative error if both warmup.time and warmupTime were specified.

Just a thought. Happy to put in a PR if this seems acceptable. Thanks for the great tool!

[Aslemammad]

This seems pretty cool! In the next major version, this would also help removing the .warmup method! Let's go with it.