SolitaryThinker
a9e5f6ee7a
Directory rename (git mv, history preserved) plus rewrite of all references: absolute imports in tests, the zero-dep runner, docstrings, comments, and the README. No behavior change. Run: python3 -m pytest v2/tests/ -q ; python3 v2/run_tests.py ; python3 -m v2.examples
59 lines
2.1 KiB
Python
59 lines
2.1 KiB
Python
"""FakeDeviceMesh — a ParallelDims-style builder, CPU-testable (design_v3 §8; torchtitan).
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> Declarative, validated, compiled to a PyTorch ``DeviceMesh`` via a ``ParallelDims``-
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> style builder (product-of-degrees validation, cached submeshes).
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On a GPU box this compiles to ``torch.distributed.device_mesh.DeviceMesh``. Here it is a
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pure-Python mesh of rank tuples so topology logic is unit-tested without GPUs.
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Degree-one axes exist as trivial groups so component code needs no special cases.
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"""
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from __future__ import annotations
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from itertools import product
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from .plan import ParallelPlan
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from .validation import validate_plan
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class FakeDeviceMesh:
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def __init__(self, plan: ParallelPlan):
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self.plan = plan
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self.order = plan.mesh_order or list(plan.axes.keys())
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self.shape = tuple(plan.degree(a) for a in self.order)
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self.world_size = plan.world_size()
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def group_ranks(self, axis: str) -> list[list[int]]:
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"""All collective groups along one axis (each is a list of global ranks)."""
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if axis not in self.order:
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return [[0]] # degree-one trivial group
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axis_idx = self.order.index(axis)
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groups: list[list[int]] = []
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ranges = [range(d) for d in self.shape]
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seen: set[tuple] = set()
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for coord in product(*ranges):
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key = coord[:axis_idx] + coord[axis_idx + 1:]
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if key in seen:
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continue
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seen.add(key)
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group = []
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for i in range(self.shape[axis_idx]):
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c = list(coord)
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c[axis_idx] = i
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group.append(self._coord_to_rank(tuple(c)))
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groups.append(group)
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return groups
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def _coord_to_rank(self, coord: tuple[int, ...]) -> int:
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rank = 0
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for c, d in zip(coord, self.shape):
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rank = rank * d + c
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return rank
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def __repr__(self) -> str:
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return f"FakeDeviceMesh(order={self.order}, shape={self.shape}, world={self.world_size})"
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def build_mesh(plan: ParallelPlan, card=None, **kw) -> FakeDeviceMesh:
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validate_plan(plan, card=card, **kw)
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return FakeDeviceMesh(plan)
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