docs/subtask.md

RoboLab Subtask System: Comprehensive Guide

This guide provides a complete reference for defining subtasks in RoboLab, covering all supported formats, logical modes, and use cases.

Table of Contents

1. Overview
2. Subtask Definitions
3. The Subtask Dataclass
4. Condition Formats
   • Format 1: Single Callable (Atomic Subtask)
   • Format 2: List of Callables
   • Format 3: List of Tuples (Callable, Score)
   • Format 4: Set of Callables
   • Format 5: Set of Tuples (Callable, Score)
   • Format 6: Dict with Single Callables
   • Format 7: Dict with List of Callables
   • Format 8: Dict with List of Tuples (Callable, Score)
   • Format 9: Dict with Set of Callables
5. Logical Modes
   • Mode 1: "all" (Default)
   • Mode 2: "any"
   • Mode 3: "choose"
6. Composite Functions
7. Sequential Subtasks
8. Scoring System
9. Effective Operations & Difficulty Scoring

---

Overview

RoboLab uses a hierarchical state machine architecture to manage complex manipulation tasks involving multiple objects and sequential execution phases.

Subtask Definitions

Subtasks are defined as a list of subtask groups, where each subtask group can handle parallel subtask checking and composite tasks such as "and"/"any"/"choose" type subtasks. Each subtask group must be complete until the next subtask state machine step.

Key Components

Subtask(conditions, logical, score, K)  ← Subtask dataclass
    ↓
SubtaskStateMachine  ← Manages sequential subtasks
    ↓
ConditionalsStateMachine  ← Manages parallel conditions
    ↓
Parallel execution with regression checking

The Subtask Dataclass

The Subtask dataclass is the core building block for defining task conditions. Each subtask must be completed before moving to the next subtask.

from robolab.core.task.subtask import Subtask

@dataclass
class Subtask:
    """Self-documenting container for a group of parallel conditions."""
    conditions: Union[Callable, list, set, dict]
    score: float = 1.0
    logical: Literal["all", "any", "choose"] = "all"
    K: Optional[int] = None  # Required when logical="choose"
    name: str = "unnamed_subtask"

Condition Formats

The conditions parameter supports 8 different formats for convenience, but will all be unified at loading time:

Format 1: Single Callable (Atomic Subtask)

Use Case: Single condition to check

from functools import partial
from robolab.core.task.subtask import Subtask
from robolab.core.task.conditionals import object_grabbed
Subtask(
    conditions=partial(object_grabbed, object='banana'),
    name="grab_banana"
)

Internal Structure: {"conditions": [(func, 1.0)]}

---

Format 2: List of Callables

Use Case: Multiple conditions as separate groups, each with equal score

Subtask(
    conditions=[
        partial(object_grabbed, object='banana'),
        partial(object_grabbed, object='rubiks_cube')
    ],
    logical="any",  # Grab ANY one object
    name="grab_any_object"
)

Internal Structure: Each callable becomes its own group with equal scores

{
    "group1": [(func1, 0.5)],
    "group2": [(func2, 0.5)]
}

---

Format 3: List of Tuples (Callable, Score)

Use Case: Multiple conditions with custom score weighting

Subtask(
    conditions=[
        (partial(object_grabbed, object='banana'), 0.3),
        (partial(object_in_container, object='banana', container='bowl'), 0.7)
    ],
    logical="all",
    name="weighted_conditions"
)

Internal Structure: Each tuple becomes its own group

{
    "group1": [(func1, 1.0)],  # Scores normalized within group
    "group2": [(func2, 1.0)]
}

---

Format 4: Set of Callables

Use Case: Same as list, but order doesn't matter semantically

Subtask(
    conditions={
        partial(object_grabbed, object='banana'),
        partial(object_grabbed, object='rubiks_cube')
    },
    logical="any",
    name="grab_any_set"
)

Note: Converted to list internally (order may vary)

---

Format 5: Set of Tuples (Callable, Score)

Use Case: Multiple conditions with scores, order-agnostic

Subtask(
    conditions={
        (partial(object_grabbed, object='banana'), 0.5),
        (partial(object_grabbed, object='rubiks_cube'), 0.5)
    },
    logical="any",
    name="weighted_set"
)

---

Format 6: Dict with Single Callables

Use Case: Explicit group names, single condition per group

Subtask(
    conditions={
        "banana": partial(object_grabbed, object='banana'),
        "cube": partial(object_grabbed, object='rubiks_cube')
    },
    logical="all",  # Both must be grabbed
    name="grab_both_explicit"
)

Internal Structure:

{
    "banana": [(func1, 1.0)],
    "cube": [(func2, 1.0)]
}

---

Format 7: Dict with List of Callables

Use Case: Multiple sequential conditions per group, equal scores

This is the most common format for complex multi-step tasks.

Subtask(
    conditions={
        "banana": [
            partial(object_grabbed, object='banana'),
            partial(object_above_bottom, object='banana', reference_object='bowl'),
            partial(object_dropped, object='banana'),
            partial(object_in_container, object='banana', container='bowl')
        ],
        "cube": [
            partial(object_grabbed, object='rubiks_cube'),
            partial(object_above_bottom, object='rubiks_cube', reference_object='bowl'),
            partial(object_dropped, object='rubiks_cube'),
            partial(object_in_container, object='rubiks_cube', container='bowl')
        ]
    },
    logical="all",  # Both banana AND cube must complete all steps
    name="pick_and_place_both"
)

Internal Structure: Each callable gets equal score within its group

{
    "banana": [(func1, 0.25), (func2, 0.25), (func3, 0.25), (func4, 0.25)],
    "cube": [(func1, 0.25), (func2, 0.25), (func3, 0.25), (func4, 0.25)]
}

Key Feature: Within each group, conditions are checked sequentially with regression checking.

---

Format 8: Dict with List of Tuples (Callable, Score)

Use Case: Full control over groups, sequences, and scores

This is the most flexible format.

Subtask(
    conditions={
        "banana": [
            (partial(object_grabbed, object='banana'), 0.1),
            (partial(object_above_bottom, object='banana', reference_object='bowl'), 0.2),
            (partial(object_dropped, object='banana'), 0.3),
            (partial(object_in_container, object='banana', container='bowl'), 0.4)
        ],
        "cube": [
            (partial(object_grabbed, object='rubiks_cube'), 0.25),
            (partial(object_above_bottom, object='rubiks_cube', reference_object='bowl'), 0.25),
            (partial(object_dropped, object='rubiks_cube'), 0.25),
            (partial(object_in_container, object='rubiks_cube', container='bowl'), 0.25)
        ]
    },
    logical="all",
    name="fully_weighted"
)

Note: Scores within each group are normalized to sum to 1.0.

---

Format 9: Dict with Set of Callables

Use Case: Order-agnostic sequential conditions per group

Subtask(
    conditions={
        "banana": {
            partial(object_grabbed, object='banana'),
            partial(object_in_container, object='banana', container='bowl')
        },
        "cube": {
            partial(object_grabbed, object='rubiks_cube'),
            partial(object_in_container, object='rubiks_cube', container='bowl')
        }
    },
    logical="any",  # Either banana OR cube completes
    name="pick_and_place_any"
)

Note: Converted to list internally.

---

Logical Modes

The logical parameter determines when a subtask group is considered complete.

Mode 1: "all" (Default)

Semantics: All groups must complete all their conditions

Progress Tracking:

Completed: 0/2 groups, Score: 0.00
  rubiks_cube: 0/4 conditions (0% complete)
  banana: 0/4 conditions (0% complete)

Completed: 0/2 groups, Score: 0.375
  rubiks_cube: 0/4 conditions (0% complete)
  banana: 3/4 conditions (75% complete)

Completed: 1/2 groups, Score: 0.75
  rubiks_cube: 2/4 conditions (50% complete)
  banana: 4/4 conditions (100% complete) ✓

Completed: 2/2 groups, Score: 1.0 ✓
  rubiks_cube: 4/4 conditions (100% complete) ✓
  banana: 4/4 conditions (100% complete) ✓

---

Mode 2: "any"

Semantics: Success when any single group completes all its conditions

Progress Tracking:

Completed: 0/3 groups, Score: 0.00
  red_block: 0/4 conditions (0% complete)
  blue_block: 0/4 conditions (0% complete)
  green_block: 0/4 conditions (0% complete)

Completed: 0/3 groups, Score: 0.50
  red_block: 0/4 conditions (0% complete)
  blue_block: 2/4 conditions (50% complete)
  green_block: 0/4 conditions (0% complete)

Completed: 1/3 groups, Score: 1.0 ✓ (blue_block completed)
  red_block: 0/4 conditions (0% complete)
  blue_block: 4/4 conditions (100% complete) ✓
  green_block: 1/4 conditions (25% complete)

---

Mode 3: "choose"

Semantics: Success when exactly K groups complete all their conditions

Important: The K parameter is required when using logical="choose".

Progress Tracking:

Completed: 0/5 groups, Score: 0.30, Need K=2
  banana_01: 0/4 conditions (0% complete)
  banana_02: 3/4 conditions (75% complete)
  banana_03: 1/4 conditions (25% complete)
  banana_04: 0/4 conditions (0% complete)
  banana_05: 2/4 conditions (50% complete)
  Top 2: [0.75, 0.50] → avg = 0.625

Completed: 1/5 groups, Score: 0.75, Need K=2
  banana_01: 0/4 conditions (0% complete)
  banana_02: 4/4 conditions (100% complete) ✓
  banana_03: 1/4 conditions (25% complete)
  banana_04: 0/4 conditions (0% complete)
  banana_05: 2/4 conditions (50% complete)
  Top 2: [1.0, 0.50] → avg = 0.75

Completed: 2/5 groups, Score: 1.0 ✓ (K=2 reached!)
  banana_01: 0/4 conditions (0% complete)
  banana_02: 4/4 conditions (100% complete) ✓
  banana_03: 1/4 conditions (25% complete)
  banana_04: 0/4 conditions (0% complete)
  banana_05: 4/4 conditions (100% complete) ✓
  Top 2: [1.0, 1.0] → avg = 1.0

---

Composite Functions

Composite functions automatically expand into multiple atomic subtasks, providing convenient shortcuts for common task patterns.

pick_and_place()

The pick_and_place() function is a composite that creates a complete pick-and-place sequence:

Signature:

@composite
def pick_and_place(
    object: str | list[str],
    container: str,
    logical: Literal["all", "any", "choose"] = "all",
    K: Optional[int] = None,
    score: float = 1.0
) -> Subtask:

Returns: A Subtask dataclass with the following structure:

{
    "object1": [
        (partial(object_grabbed, object='object1'), 0.25),
        (partial(object_above_bottom, object='object1', reference_object='container'), 0.25),
        (partial(object_dropped, object='object1'), 0.25),
        (partial(object_in_container, object='object1', container='container'), 0.25)
    ],
    "object2": [
        # ... same sequence for object2
    ]
}

Examples:

from robolab.core.task.conditionals import pick_and_place

# Example 1: Both objects must be placed
subtasks = [
    pick_and_place(
        object=["rubiks_cube", "banana"],
        container="bowl",
        logical="all",
        score=1.0
    )
]

# Example 2: Any one object is sufficient
subtasks = [
    pick_and_place(
        object=["red_block", "blue_block", "green_block"],
        container="bin",
        logical="any",
        score=0.5
    )
]

# Example 3: Exactly 2 out of 3 objects
subtasks = [
    pick_and_place(
        object=["banana_01", "banana_02", "banana_03"],
        container="bowl",
        logical="choose",
        K=2,
        score=1.0
    )
]

NOTE Do NOT use for termination conditions (use object_placed_in_container instead). Terminations check final state only, while subtasks track intermediate progress.

---

Sequential Subtasks

Multiple Subtask objects can be chained to create multi-stage tasks. Each stage must complete before the next begins.

Basic Sequential Example

subtasks = [
    # Stage 1:
    Subtask(...),
    # Stage 2:
    Subtask(...)
]

Mixed Logical Modes

subtasks = [
    # Stage 1: Pick any one block, must be complete before starting the next one
    pick_and_place(
        object=["red_block", "blue_block"],
        container="bowl",
        logical="any",
        score=0.3
    ),

    # Stage 2: Both fruits must be placed.
    pick_and_place(
        object=["banana", "apple"],
        container="bowl",
        logical="all",
        score=0.4
    ),

]

Progress Tracking:

Overall Progress: 0/2 stages complete (0%)
Current Stage 1: logical='any', score=0.3
  red_block: 2/4 (50%)
  blue_block: 0/4 (0%)

Overall Progress: 1/2 stages complete (50%)
Current Stage 2: logical='all', score=0.4
  banana: 0/4 (0%)
  apple: 0/4 (0%)

Overall Progress: 2/2 stages complete (100%) ✓

---

Scoring System

Score Normalization

Within Each Group: Condition scores are relative to each other, normalized to sum to 1.0

# Before normalization
conditions = {
    "banana": [
        (func1, 0.1),
        (func2, 0.2),
        (func3, 0.3)
    ]
}
# Total: 0.6

# After normalization (automatic)
conditions = {
    "banana": [
        (func1, 0.167),  # 0.1 / 0.6
        (func2, 0.333),  # 0.2 / 0.6
        (func3, 0.500)   # 0.3 / 0.6
    ]
}
# Total: 1.0

Across Subtasks: Subtasks are also relative to each other, which will be normalized to 1.

subtasks = [
    Subtask(..., score=0.2),  # 20% of total task
    Subtask(..., score=0.5),  # 50% of total task
    Subtask(..., score=0.3)   # 30% of total task
]
# These don't need to sum to 1.0, but they define relative weights

A visual example of subtask state tracking for a group of objects:

Running RubiksCubeBananaTaskHomeOffice_0: 'put the cube and banana in the bowl'


 19%|█████████████████▏                                                                        | 90/470 [00:13<01:09,  5.45it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 0, 'banana': 1}
Objects and their current subtasks:
  rubiks_cube (step 0/4):
     0. ❌ object_grabbed(object=rubiks_cube) <-- CURRENT
     1. ❌ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (pending)
     2. ❌ object_dropped(object=rubiks_cube) (pending)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 1/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ❌ object_above_bottom_surface(object=banana, surface=bowl) <-- CURRENT
     2. ❌ object_dropped(object=banana) (pending)
     3. ❌ object_in_container(object=banana, container=bowl, tolerance=0.05) (pending)
==================================================
Subtask status: i: 90, status: {'status': <SubtaskStatusCode.OBJECT_GRABBED_SUCCESS: 120>, 'completed': 1, 'total': 8, 'info': "success: object_grabbed(object='banana');"}


 30%|██████████████████████████▉                                                              | 142/470 [00:23<01:11,  4.56it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 0, 'banana': 2}
Objects and their current subtasks:
  rubiks_cube (step 0/4):
     0. ❌ object_grabbed(object=rubiks_cube) <-- CURRENT
     1. ❌ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (pending)
     2. ❌ object_dropped(object=rubiks_cube) (pending)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 2/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ❌ object_dropped(object=banana) <-- CURRENT
     3. ❌ object_in_container(object=banana, container=bowl, tolerance=0.05) (pending)
==================================================
Subtask status: i: 142, status: {'status': <SubtaskStatusCode.OBJECT_ABOVE_BOTTOM_SURFACE_SUCCESS: 160>, 'completed': 2, 'total': 8, 'info': "success: object_above_bottom_surface(object='banana', surface='bowl');"}


 39%|██████████████████████████████████▊                                                      | 184/470 [00:32<01:02,  4.57it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 0, 'banana': 3}
Objects and their current subtasks:
  rubiks_cube (step 0/4):
     0. ❌ object_grabbed(object=rubiks_cube) <-- CURRENT
     1. ❌ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (pending)
     2. ❌ object_dropped(object=rubiks_cube) (pending)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 3/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ❌ object_in_container(object=banana, container=bowl, tolerance=0.05) <-- CURRENT
==================================================
Subtask status: i: 184, status: {'status': <SubtaskStatusCode.OBJECT_DROPPED_SUCCESS: 140>, 'completed': 3, 'total': 8, 'info': "success: object_dropped(object='banana');"}


 39%|███████████████████████████████████                                                      | 185/470 [00:32<00:57,  4.92it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 0, 'banana': 4}
Objects and their current subtasks:
  rubiks_cube (step 0/4):
     0. ❌ object_grabbed(object=rubiks_cube) <-- CURRENT
     1. ❌ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (pending)
     2. ❌ object_dropped(object=rubiks_cube) (pending)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 4/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ✅ object_in_container(object=banana, container=bowl, tolerance=0.05) (completed)
==================================================
Subtask status: i: 185, status: {'status': <SubtaskStatusCode.OBJECT_IN_CONTAINER_SUCCESS: 110>, 'completed': 4, 'total': 8, 'info': "success: object_in_container(object='banana', container='bowl', tolerance=0.05). All subtasks complete for banana.;"}


 88%|██████████████████████████████████████████████████████████████████████████████▍          | 414/470 [01:11<00:10,  5.43it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 1, 'banana': 4}
Objects and their current subtasks:
  rubiks_cube (step 1/4):
     0. ✅ object_grabbed(object=rubiks_cube) (completed)
     1. ❌ object_above_bottom_surface(object=rubiks_cube, surface=bowl) <-- CURRENT
     2. ❌ object_dropped(object=rubiks_cube) (pending)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 4/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ✅ object_in_container(object=banana, container=bowl, tolerance=0.05) (completed)
==================================================
Subtask status: i: 414, status: {'status': <SubtaskStatusCode.OBJECT_GRABBED_SUCCESS: 120>, 'completed': 5, 'total': 8, 'info': "success: object_grabbed(object='rubiks_cube');"}


 93%|██████████████████████████████████████████████████████████████████████████████████▉      | 438/470 [01:17<00:07,  4.56it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 2, 'banana': 4}
Objects and their current subtasks:
  rubiks_cube (step 2/4):
     0. ✅ object_grabbed(object=rubiks_cube) (completed)
     1. ✅ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (completed)
     2. ❌ object_dropped(object=rubiks_cube) <-- CURRENT
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (pending)
  banana (step 4/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ✅ object_in_container(object=banana, container=bowl, tolerance=0.05) (completed)
==================================================
Subtask status: i: 438, status: {'status': <SubtaskStatusCode.OBJECT_ABOVE_BOTTOM_SURFACE_SUCCESS: 160>, 'completed': 6, 'total': 8, 'info': "success: object_above_bottom_surface(object='rubiks_cube', surface='bowl');"}


 97%|██████████████████████████████████████████████████████████████████████████████████████▎  | 456/470 [01:20<00:02,  4.73it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 3, 'banana': 4}
Objects and their current subtasks:
  rubiks_cube (step 3/4):
     0. ✅ object_grabbed(object=rubiks_cube) (completed)
     1. ✅ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (completed)
     2. ✅ object_dropped(object=rubiks_cube) (completed)
     3. ❌ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) <-- CURRENT
  banana (step 4/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ✅ object_in_container(object=banana, container=bowl, tolerance=0.05) (completed)
==================================================
Subtask status: i: 456, status: {'status': <SubtaskStatusCode.OBJECT_DROPPED_SUCCESS: 140>, 'completed': 7, 'total': 8, 'info': "success: object_dropped(object='rubiks_cube');"}


 97%|██████████████████████████████████████████████████████████████████████████████████████▋  | 458/470 [01:21<00:02,  5.18it/s]
--------------------------------------------------
SUBTASK STATE
--------------------------------------------------
Current Object Progress: {'rubiks_cube': 4, 'banana': 4}
Objects and their current subtasks:
  rubiks_cube (step 4/4):
     0. ✅ object_grabbed(object=rubiks_cube) (completed)
     1. ✅ object_above_bottom_surface(object=rubiks_cube, surface=bowl) (completed)
     2. ✅ object_dropped(object=rubiks_cube) (completed)
     3. ✅ object_in_container(object=rubiks_cube, container=bowl, tolerance=0.05) (completed)
  banana (step 4/4):
     0. ✅ object_grabbed(object=banana) (completed)
     1. ✅ object_above_bottom_surface(object=banana, surface=bowl) (completed)
     2. ✅ object_dropped(object=banana) (completed)
     3. ✅ object_in_container(object=banana, container=bowl, tolerance=0.05) (completed)
==================================================
Subtask status: i: 458, status: {'status': <SubtaskStatusCode.OBJECT_IN_CONTAINER_SUCCESS: 110>, 'completed': 8, 'total': 8, 'info': "success: object_in_container(object='rubiks_cube', container='bowl', tolerance=0.05). All subtasks complete for rubiks_cube.;"}

---

Subtask Counts & Difficulty Scoring

Tasks are automatically assigned a difficulty score and difficulty label based on their subtask structure and attributes. This scoring is deterministic and computed from the task definition — no manual labeling is required.

Subtask Counts (num_subtasks)

The num_subtasks metric counts the number of distinct manipulation actions the robot must perform, accounting for the subtask's logical mode:

Logical Mode	Subtask Count
"all"	Number of object groups (every group must complete)
"any"	1 (only one group needs to complete)
"choose"	K (exactly K groups must complete)

The total is summed across all sequential stages in the task. For example, a task with two sequential stages — the first requiring "all" of 2 objects, the second "any" of 3 — has 2 + 1 = 3 subtasks.

See count_subtasks() in robolab/core/task/subtask_utils.py.

Difficulty Score

The difficulty score combines manipulation volume with skill complexity:

difficulty_score = num_subtasks + max(skill_weight)

where max(skill_weight) is the highest weight among the task's attributes. The skill weights are:

Weight	Attributes
0	color, semantics, size, conjunction, vague
+1	spatial
+2	counting, sorting, stacking, affordance
+3	reorientation

Difficulty Labels

Labels are assigned based on the score using fixed thresholds:

Label	Score Range
simple	score <= 2
moderate	score 3–4
complex	score >= 5

Examples

Task	Subtasks	Max Skill Weight	Score	Label
RubiksCubeTask (1 pick-and-place, no special attrs)	1	0	1	simple
BowlStackingLeftOnRightTask (1 subtask, spatial)	1	1 (spatial)	2	simple
Stack3RubiksCubeTask (2 subtasks, stacking)	2	2 (stacking)	4	moderate
BlockStackingSpecifiedOrderTask (3 subtasks, stacking+color)	3	2 (stacking)	5	complex
ReorientAllMugsTask (4 subtasks, reorientation)	4	3 (reorientation)	7	complex

Implementation

The scoring constants and function live in robolab/core/task/subtask_utils.py:

• SKILL_WEIGHTS — attribute-to-weight mapping
• DIFFICULTY_THRESHOLDS — (simple_max, moderate_max) tuple
• compute_difficulty_score(num_subtasks, attributes) — returns (score, label)

The metadata pipeline (robolab/tasks/_utils/load_task_info.py) automatically populates num_subtasks, difficulty_score, and difficulty_label for each task. Summary statistics are available via:

python robolab/tasks/_utils/compute_task_statistics.py --difficulty
python robolab/tasks/_utils/compute_task_statistics.py --difficulty -v  # full task list