ADR-0027: Megatron TP API + worker-wait generalization + mp.spawn
Implements ADR-0027 Phase 2 end-to-end. All 559 tests pass (was 523 + 1 xfail; ring_default_ws strict-xfail is now resolved). D0 — Worker-wait generalization (context.py): - _pending_worker_waits queue on RuntimeContext. - ctx.wait(h) in worker context defers to main via g.parent.switch(). Fast-path for already-completed handles. - Worker API is unchanged: tensor deploy, launch, etc. still look synchronous; they're transparently cooperatively scheduled. - Solves ADR-0024 Phase B kernel-greenlet orphan bug (env.run now only ever drives from main; kernel _parent is always main). D0.5 — Host-read barrier (tensor.py): - Explicit _HOST_READ_BARRIERS registry (T5.g closed-set via code review, not reflection-magic). - numpy/data/__getitem__/__repr__ drain pending worker-waits before host-observable read. - copy_: source-side barrier via source.numpy(). Target-side write barrier is intentionally NOT applied — global pending target barrier prematurely drains cross-rank collectives → deadlock. - Collective pending is excluded from barrier drain condition (collective is cross-rank; its own yield in all_reduce covers the invariant naturally). D1 — torch.multiprocessing.spawn (runtime_api/multiprocessing.py): - API signature parity with real PyTorch spawn; execution is cooperative greenlet scheduler (process isolation etc. are explicit non-goals per D1.0). - _drain_pending drains worker-waits then collectives in one barrier, loop-until-empty. - Round-based exception handling with SystemExit sibling abort + SpawnException(errors) wrapping root-cause ranks. - RuntimeContext attaches ctx.multiprocessing in __post_init__. - benches/ccl_allreduce.py hand-rolled loop collapses to one torch.multiprocessing.spawn call. D2–D6 — kernbench.tp package: - parallel_state: initialize_model_parallel, get_*_rank, get_*_world_size, with weak active-ctx registry in context.py. - layers: ColumnParallelLinear, RowParallelLinear (shape-only primitives — fp16 gemm via tl.load + tl.dot + tl.store). - kernels: _gemm_kernel used by TP layers (self-contained; no bench dependency). - primitives / mappings stubs per D6/D8. Data-path fixes (surfaced by TP gemm + all_reduce sequence): - sim_engine/op_log.py: dma_write snapshot is skipped for TCM sources (PE scratch is repopulated by Phase 2 math/gemm replay — capturing Phase-1-time snapshot picked up STALE data from prior kernel's output aliased at the same scratch addr, causing the later kernel's dma_write to overwrite Phase 2 result with stale value). - sim_engine/op_log.py + sim_engine/data_executor.py: per-operand space recorded on GemmCmd and composite gemm records so HBM-resident operands (tl.load output) don't default to TCM during replay. - runtime_api/context.py: ctx.zeros writes zero-init to MemoryStore at VA keys so kernels reading via VA see deterministic init even without explicit copy_(). Tests (Phase 1 + Phase 2): - test_worker_wait_drain (T3): orphan invariant + resume + multi-rank drain + idempotency + exception propagation. - test_mp_spawn (T4): spawn shape + bind + SpawnException scope. - test_host_read_barrier (T5): barrier contract per entry-point + closed-set registry check. - test_tp_parallel_state (T1): initialize + rank lookup. - test_tp_layers (T2): shape + deterministic numerical correctness (concat-matmul equality for RowParallel, not mean-only). - test_tp_mlp (T6): full 2-layer MLP with deterministic weight numerical match + rank-consistency post all-reduce. - test_ccl_allreduce_matrix: ring_default_ws xfail removed (T7). Regression: 523 pre + 35 new + 1 ex-xfail = 559 passed, 1 intentional skip (T3.e historical failure documentation). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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"""ADR-0027 T2: TP layer shape + numerical correctness (D4/D5).
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Phase 1: ``kernbench.tp.layers`` doesn't exist → import failure. Phase 2
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lands D4/D5 and T2 passes with deterministic non-zero weight patterns.
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"""
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from __future__ import annotations
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import numpy as np
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import pytest
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def _make_ctx(topology):
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from kernbench.runtime_api.context import RuntimeContext
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from kernbench.runtime_api.types import DeviceSelector
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from kernbench.sim_engine.engine import GraphEngine
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engine = GraphEngine(topology.topology_obj, enable_data=True)
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return RuntimeContext(
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engine=engine,
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target_device=DeviceSelector("all"),
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correlation_id="test_t2",
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spec=topology.topology_obj.spec,
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)
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# ── Shape / structural ───────────────────────────────────────────────
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def test_column_parallel_weight_shape_per_rank(topology):
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"""ColumnParallelLinear weight per rank is (in_features, out // ws)."""
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import kernbench.tp as tp
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from kernbench.runtime_api.tensor import Tensor
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with _make_ctx(topology) as ctx:
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ctx.distributed.init_process_group(backend="ahbm")
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ws = ctx.distributed.get_world_size()
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tp.initialize_model_parallel(ws)
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def _worker(rank: int):
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ctx.ahbm.set_device(rank)
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fc = tp.ColumnParallelLinear(
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in_features=256, out_features=512, torch=ctx,
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)
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assert fc.weight.shape == (256, 512 // ws)
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ctx.multiprocessing.spawn(_worker, args=(), nprocs=ws)
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def test_row_parallel_weight_shape_per_rank(topology):
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"""RowParallelLinear weight per rank is (in_features // ws, out_features)."""
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import kernbench.tp as tp
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with _make_ctx(topology) as ctx:
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ctx.distributed.init_process_group(backend="ahbm")
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ws = ctx.distributed.get_world_size()
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tp.initialize_model_parallel(ws)
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def _worker(rank: int):
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ctx.ahbm.set_device(rank)
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fc = tp.RowParallelLinear(
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in_features=512, out_features=256, torch=ctx,
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)
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assert fc.weight.shape == (512 // ws, 256)
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ctx.multiprocessing.spawn(_worker, args=(), nprocs=ws)
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# ── T2.a: ColumnParallel deterministic numerical ─────────────────────
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def test_column_parallel_forward_matches_matmul(topology):
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"""T2.a: ColumnParallelLinear.forward output == x @ W_rank (rtol 1e-2)."""
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import kernbench.tp as tp
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from kernbench.runtime_api.tensor import Tensor
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with _make_ctx(topology) as ctx:
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ctx.distributed.init_process_group(backend="ahbm")
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ws = ctx.distributed.get_world_size()
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tp.initialize_model_parallel(ws)
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M = 4
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D_in, D_out = 32, 32 * ws
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def _worker(rank: int):
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ctx.ahbm.set_device(rank)
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fc = tp.ColumnParallelLinear(
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in_features=D_in, out_features=D_out, torch=ctx,
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)
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# Deterministic non-zero weight: rank-scaled constant.
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k_local = D_out // ws
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weight_np = np.full(
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(D_in, k_local), 0.01 * (rank + 1), dtype=np.float16,
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)
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src = Tensor(shape=(D_in, k_local), dtype="f16", name="host_w")
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src._host_buffer = weight_np
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fc.weight.copy_(src)
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# Input: full-replicated constant.
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x_np = np.full((M, D_in), 0.5, dtype=np.float16)
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x = ctx.zeros(
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(M, D_in), dtype="f16",
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dp=_replicate_dp(), name=f"t2a_x_r{rank}",
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)
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hx = Tensor(shape=x_np.shape, dtype="f16", name="host_x")
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hx._host_buffer = x_np
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x.copy_(hx)
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y = fc.forward(x)
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out = y.numpy()
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expected = x_np.astype(np.float32) @ weight_np.astype(np.float32)
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assert out.shape == (M, k_local)
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assert np.allclose(out.astype(np.float32), expected,
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rtol=1e-2, atol=1e-2), (
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f"rank {rank}: output does not match x @ W_local"
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)
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ctx.multiprocessing.spawn(_worker, args=(), nprocs=ws)
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# ── T2.b: RowParallel observable equality ────────────────────────────
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def test_row_parallel_forward_concat_matmul_equality(topology):
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"""T2.b (primary): RowParallel output == concat(x) @ concat(W) (all-reduced)."""
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import kernbench.tp as tp
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from kernbench.runtime_api.tensor import Tensor
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with _make_ctx(topology) as ctx:
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ctx.distributed.init_process_group(backend="ahbm")
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ws = ctx.distributed.get_world_size()
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tp.initialize_model_parallel(ws)
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M = 4
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D_in, D_out = 32 * ws, 32 # must divide ws evenly
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results: dict[int, np.ndarray] = {}
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def _worker(rank: int):
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ctx.ahbm.set_device(rank)
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fc = tp.RowParallelLinear(
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in_features=D_in, out_features=D_out, torch=ctx,
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)
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# Per-rank W_k = constant 0.01 * (rank + 1)
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n_local = D_in // ws
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weight_np = np.full(
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(n_local, D_out), 0.01 * (rank + 1), dtype=np.float16,
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)
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src = Tensor(shape=weight_np.shape, dtype="f16", name="host_w")
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src._host_buffer = weight_np
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fc.weight.copy_(src)
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# Input x_k = constant 0.1 * (rank + 1) (pretending it was
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# column-sharded from upstream).
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x_np = np.full((M, n_local), 0.1 * (rank + 1), dtype=np.float16)
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x = ctx.zeros(
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(M, n_local), dtype="f16",
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dp=_replicate_dp(), name=f"t2b_x_r{rank}",
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)
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hx = Tensor(shape=x_np.shape, dtype="f16", name="host_x")
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hx._host_buffer = x_np
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x.copy_(hx)
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y = fc.forward(x)
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results[rank] = y.numpy().astype(np.float32)
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ctx.multiprocessing.spawn(_worker, args=(), nprocs=ws)
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# Host-side reference: compute sum_r (x_r @ W_r) = y (same on all ranks).
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expected = np.zeros((M, D_out), dtype=np.float32)
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n_local = D_in // ws
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for r in range(ws):
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x_r = np.full((M, n_local), 0.1 * (r + 1), dtype=np.float32)
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w_r = np.full((n_local, D_out), 0.01 * (r + 1), dtype=np.float32)
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expected += x_r @ w_r
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for r, out in results.items():
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assert np.allclose(out, expected, rtol=1e-2, atol=1e-2), (
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f"rank {r}: all-reduced output != expected partial sum"
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)
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# ── T2.c: rank-consistency post all-reduce ───────────────────────────
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def test_row_parallel_rank_identity_post_all_reduce(topology):
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"""T2.c: after all_reduce, all ranks see elementwise-identical output."""
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import kernbench.tp as tp
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from kernbench.runtime_api.tensor import Tensor
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with _make_ctx(topology) as ctx:
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ctx.distributed.init_process_group(backend="ahbm")
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ws = ctx.distributed.get_world_size()
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tp.initialize_model_parallel(ws)
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M = 2
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D_in, D_out = 16 * ws, 16
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results: dict[int, np.ndarray] = {}
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def _worker(rank: int):
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ctx.ahbm.set_device(rank)
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fc = tp.RowParallelLinear(
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in_features=D_in, out_features=D_out, torch=ctx,
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)
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n_local = D_in // ws
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weight_np = np.full((n_local, D_out), 0.01, dtype=np.float16)
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src = Tensor(shape=weight_np.shape, dtype="f16", name="host_w")
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src._host_buffer = weight_np
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fc.weight.copy_(src)
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x_np = np.full((M, n_local), 0.1, dtype=np.float16)
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x = ctx.zeros(
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(M, n_local), dtype="f16",
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dp=_replicate_dp(), name=f"t2c_x_r{rank}",
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)
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hx = Tensor(shape=x_np.shape, dtype="f16", name="host_x")
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hx._host_buffer = x_np
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x.copy_(hx)
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y = fc.forward(x)
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results[rank] = y.numpy()
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ctx.multiprocessing.spawn(_worker, args=(), nprocs=ws)
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ref = results[0]
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for r, out in results.items():
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assert np.allclose(out, ref, rtol=1e-2, atol=1e-2), (
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f"rank {r} output differs from rank 0 — all_reduce failed to make "
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f"outputs elementwise identical"
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)
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def _replicate_dp():
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from kernbench.policy.placement.dp import DPPolicy
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return DPPolicy(cube="replicate", pe="replicate", num_cubes=1, num_pes=1)
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