IssueTracker

Component used: collection-ktx Version used: 1.4.0

I'm using MutableLongLongMap to store a map of ids to sizes. The map is fairly large, and I need to increment values several times for many keys.

So I wrote extension functions that look like this:

inline fun MutableLongLongMap.increase(
  key: Long,
  addedValue: Long,
): Long {
  return updateAndGet(key, default = 0) { valueToUpdate ->
    valueToUpdate + addedValue
  }
}

inline fun MutableLongLongMap.updateAndGet(
  key: Long,
  default: Long,
  updateValueBlock: (Long) -> Long
): Long {
  val valueToUpdate = getOrDefault(key, default)
  val updatedValue = updateValueBlock(valueToUpdate)
  set(key, updatedValue)
  return updatedValue
}

This works, but if you look at what updateAndGet() does under the hood, you'll see that it's calling MutableLongLongMap.findKeyIndex() to get the value then MutableLongLongMap.findInsertIndex() to set the value. Since we know we're going to insert anyway, a better implementation of updateAndGet() could do the hashing & scanning work only once, then get the value (or default), run the update lambda then update the value array.