Generate UUIDs on demand

[hubertp]

Pull Request Description

Trying to avoid expensive UUID.randomUUID() unless we reallly need it.

Closes #8716.

Important Notes

Some improvement:

FWIW Total Time for a Hello World example

Before

After

Memory usage

Before

After

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed, the GUI was tested when built using ./run ide build.

[JaroslavTulach]

I am glad the with LazyId solution seems to be working. Everything is nicely green. And the startup benchmarks seem to be a bit improved too.

Can you manually check the amount of UUID in memory before and now at the end of execution? The memory consumption should dramatically decrease, right?

Measuring how much UUID has been allocated on the heap (and GCed) would be interesting as well, but I am not sure how to perform such measurement reliably.

[JaroslavTulach]

null is "cheaper" value than any other value. Occupies nothing in the heap.

[JaroslavTulach]

LazyId trait! That sounds promising.

[JaroslavTulach]

I thought that the

    if (_id == null) {
      _id = randomId()
    }
    _id

would be here, in this id method. That this id should never return null.

Wouldn't it be getter to:

override def id: UUID @Identifier = getId()

?

[hubertp]

The problem is that in IR definitions we use .id all over the place and we do not want to initialize it at that point. Only at the point when it is actually used, .getId(), outside of IR.

[JaroslavTulach]

Can you make id private then? Package private or subtree private? Or there could be:

def isIdInitialized(): Boolean

and we could write

id = if (keepIdentifiers && isIdInitialized()) getId() else null

everywhere.

[4e6]

If it is only used within IRs, we can mark it protected

[hubertp]

Added screenshots that illustrate improvement on a simple Hello World program.

[Akirathan]

Very nice and elegant improvement. Congratulations.