Grasp Generation in PDDLStream planning

[sea-bass]

It's finally here!

Closes #45

[sea-bass]

I deeply dislike these rules. If you have any thoughts on how to better convert an arbitrary PDDLStream plan to an actual action plan, I'd be interested in hearing it.

Even if we move the PDDLStream mappings/primitives to a user workspace, users will also need to touch this code if they're doing anything "non-standard" per our examples.

[AndyZe]

probably functional programming would help, i.e. the user can pass a list of functions to pddlstream_solution_to_plan(). Most of those functions will probably come from the pyrobosim module but sometimes it might come from the user's custom module.

I'm not an expert on that at all, especially not in Python

[sea-bass]

That's very good! You can just pass a dictionary mapping from the action name to a function that makes the action itself.

In fact, that's exactly how PDDLStream does the mappings, as seen in the mappings.py file

[AndyZe]

Hmm, first shot at testing this:

python3 examples/demo_pddl.py --example 01_simple --verbose --> Works fine

python3 examples/demo_pddl.py --example 05_nav_grasp_stream --verbose -->

> FileNotFoundError: [Errno 2] No such file or directory: '/home/andy/.local/lib/python3.10/site-packages/pyrobosim/utils/../data/pddlstream/domains/05_nav_grasp_stream/domain.pddl'

Resolved: I hadn't checked out the right branch, and also needed to run pip install ./pyrobosim

[sea-bass]

Hmm, first shot at testing this:

python3 examples/demo_pddl.py --example 01_simple --verbose --> Works fine

python3 examples/demo_pddl.py --example 05_nav_grasp_stream --verbose -->

FileNotFoundError: [Errno 2] No such file or directory: '/home/andy/.local/lib/python3.10/site-packages/pyrobosim/utils/../data/pddlstream/domains/05_nav_grasp_stream/domain.pddl'

I think that may just be that a colcon build and/or pip install is needed?

[AndyZe]

also don't see obs and pobs defined above

[sea-bass]

The exists predicate is kind of like a lambda, in that you define new variables that only exist in that scope.

[AndyZe]

is that what makes it a "derived" predicate?

[sea-bass]

No, but both derived predicates and things like exists are syntactic sugar for PDDL.

A derived predicate just defines a shorthand for complex logic with existing predicates to write done as a single predicate. Think of it like a "function".

exists is similarly some common logical expression you can use in place of a giant string of ANDs and ORs. There are others like imply, forall, etc. as shown here: https://planning.wiki/ref/pddl/domain#exists

[AndyZe]

?s isn't defined above. Is it a sampled location?

Also, is this reading of the logic correct:

• entity is an object type OR robot type
• AND ?loc is a location type
• entity is at ?loc OR
  • ?s exists AND:
    • ?loc is a room
    • AND ?s is a location
    • AND ?entity is at ?s
    • AND ?s is at room ?loc

Pretty complicated! In other words, the sampled location and ?loc are the same and ?entity is there?

[sea-bass]

The exists predicate is kind of like a lambda, in that you define new variables that only exist in that scope.

And yep, your reading of that logic is exactly right. Those Has and HasAll derived predicates are pretty tough to get working, which is why PDDL domain definition is kind of an art and people want to get away from it.