[Perf] Tiles 5: add Cholesky benchmark demo#483
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TypeCheck has allow_undefined_visitor=true, so removing this override is a no-op. The original code was actively wrong (overwriting correct ret_type with i32), but nothing downstream relied on ret_type from the type_check pass for InternalFuncStmt, so the bug was latent. Removing the override eliminates the misleading TODO and prevents a future pass from accidentally depending on the wrong type.
…tests - Parametrize ger_sub and cholesky tests over f32/f64 dtypes - Use tighter tolerance (1e-10) for f64, 1e-5 for f32 - Parametrize cholesky over src_offset (0, 5, 32) and dst_delta (0, 3, 16) - Verify untouched regions of dst array remain at sentinel value
…olesky_ _ger_sub: 34 lines → 4 lines cholesky_: 224 lines → 22 lines
Quadrants DSL types don't carry operator overloads in their stubs, so pyright can't verify +=, *, /, > on shuffled values.
Fix scipy reference computation: solve X @ L^T = B requires solve_triangular(L, B.T) not solve_triangular(L, B, trans='T'). Add type: ignore[reportOperatorIssue] for DSL operator expressions in _trsm that pyright can't verify.
…_eye_
Replace 16-way explicit register access with loop-based _get_col/_set_col
helpers, eliminating ~145 lines of boilerplate. Also fix trsm test reference
computation (was computing B^T @ L^{-1} instead of B @ L^{-T}).
…e16x16 - Slice-based load/store: arr[r0:r1, c0:c1] for 2D and arr[b, r0:r1, c0:c1] for 3D - qd.outer(a, b) deferred proxy for augmented assignment (t -= qd.outer(a, b)) - _TileSliceProxy, _VecSliceProxy, _TileRefProxy for deferred subscript evaluation - AST purity exemptions for quadrants-internal code - _quadrants_internal flag on Tile struct
The purity checker only flags int/float/Field attribute accesses inside kernels. Tile() and Tile.zeros() don't trigger this, and Tile.SIZE is only accessed in plain Python, not inside kernels.
Add tile16.md covering tile creation, slice load/store, rank-1 updates, Cholesky, and triangular solve. Remove the unused _quadrants_internal getattr escape hatch from the purity checker (file-level check suffices). Add test for Tile.SIZE access inside a kernel.
…top in slices Update tile16 doc examples to use Tile.SIZE. Enforce that both start and stop indices are provided in tile/vec slice syntax (previously stop defaulted to start+16 when omitted). Reorder _TileSliceProxy.__init__ args to match (row_start, row_stop, col_start, col_stop).
The if-condition checking all four slice indices was too long for black. The test_tile16_load_missing_start_raises regex didn't match the updated error message after requiring both start and stop indices.
- test_tile16_outer_symmetric_same_variable: passes same variable for both args to qd.outer(v, v) - test_tile16_vec_proxy_ger_sub_3d: column vector load from 3D array via arr[batch, r0:r1, col] - test_outer_composition_raises: verifies qd.outer(a,b) + qd.outer(c,d) raises TypeError
…errors Only intercept 2D/1D array slices for tile proxy creation when _tile16_cache is non-empty (i.e., _make_tile16x16 has been called). Non-tile programs now get the original "does not support slice" error. Add _DeferredProxyMixin with __add__, __sub__, __mul__, __getitem__, and __repr__ that raise clear TypeErrors explaining the proxy is only valid in tile operations.
Check isinstance(value, t) against cached tile types before creating a _TileRefProxy for struct[:] subscripts. Non-tile structs now fall through to normal subscript handling.
Metal and Vulkan backends don't support f64. Exclude them from test_tile16_f64_roundtrip_into_f32_array and test_proxy_default_dtype_survives_reinit.
The early return on cache hit was bypassing the CPU backend guard, so after a GPU init the cache would let a subsequent CPU init skip the QuadrantsSyntaxError. Move the cache check after the arch guard.
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Opus actions to address 'bad points' in the description: User: modify the demo to work on qd.gpuAssistant: Done. Changed User: add a unit test to qaudrants unit tests that smoke tests that cholesksy_blocked.md runs to completion without crashing …add a unit test to qaudrants unit tests that smoke tests that cholesksy_blocked.md runs to completion without crashing (exit code 0). This should run on qd.gpu Assistant: Let me find existing test patterns and see if there are any subprocess-based smoke tests already. User: sorry, cholesky_blocked.pyAssistant: Let me check how the existing test file for tile16 is structured and see test_utils.test() usage: Let me check how Now let me check how The demo uses module-level Now add the smoke test at the end of the file: Done. Added User: run hte test, hceck it passesAssistant: Passes on both CUDA and Vulkan. 15 seconds total. |
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| def test_tile16_cholesky_blocked_demo(): | ||
| """Smoke-test that misc/demos/cholesky_blocked.py runs to completion.""" | ||
| demo = Path(__file__).resolve().parents[2] / "misc" / "demos" / "cholesky_blocked.py" | ||
| result = subprocess.run([sys.executable, str(demo)], capture_output=True, text=True, timeout=300) |
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This test is parametrized with @test_utils.test(arch=qd.gpu), but the subprocess command does not pass the active req_arch to the child. The demo then initializes with qd.init(arch=qd.gpu), so on multi-backend machines the vulkan/metal parametrizations can still run on a different backend (typically CUDA), which makes this test miss backend-specific regressions. Pass the current backend name to the script and initialize that exact arch in the child process.
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| def test_tile16_cholesky_blocked_demo(): | ||
| """Smoke-test that misc/demos/cholesky_blocked.py runs to completion.""" | ||
| demo = Path(__file__).resolve().parents[2] / "misc" / "demos" / "cholesky_blocked.py" | ||
| result = subprocess.run([sys.executable, str(demo)], capture_output=True, text=True, timeout=300) |
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The smoke test currently invokes the benchmark script with its hardcoded heavy settings (N_ENVS=4096, WARMUP=50, ITERS=200), which means one unit test run performs hundreds of large GPU launches and allocates several large fields. Because this test is not marked run_in_serial and runs in a separate subprocess, it bypasses the per-test CUDA memory throttling used in tests/python/conftest.py, increasing the chance of OOM/timeouts when xdist runs tests concurrently. Add a lightweight test mode (or CLI/env overrides) and use that here.
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| H[i0 + r, k0 + c] = (H[i0 + r, k0 + c] - dot) / H[k0 + c, k0 + c] | ||
| qd.simt.block.sync() | ||
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| # Write result to global memory | ||
| for row in range(N): | ||
| c = tid | ||
| while c <= row: | ||
| L_blocked_field[env, row, c] = H[row, c] | ||
| c += TILE | ||
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| # --------------------------------------------------------------------------- | ||
| # Kernel 3: Tile16x16 blocked Cholesky (16 threads, no shared memory) |
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🟡 The guard 'if r < TILE' in the triangular solve section of cholesky_blocked() is vacuously true and never skips any thread. Since tid = idx % TILE with TILE=16, r = tid is always in [0, 15], so 'if r < TILE' is always True. The dead conditional can be removed; it may mislead readers by analogy with the meaningful 'if row < TILE' guard in the Crout diagonal section above, where row = col + 1 + tid can genuinely exceed TILE.
Extended reasoning...
What the bug is: In the triangular solve loop inside cholesky_blocked() (lines 180-192 of misc/demos/cholesky_blocked.py), the code sets r = tid and then guards the body with 'if r < TILE'. Since tid = idx % TILE (with TILE=16), tid is always in the range [0, 15]. Setting r = tid means r is always in [0, 15], so 'if r < TILE' — i.e. 'if r < 16' — is always True and the guard never prevents execution of the body.
The specific code path: In cholesky_blocked(), the outer loop sets tid = idx % TILE (TILE=16), so tid is in {0, 1, ..., 15}. In the off-diagonal block triangular solve:
for c in range(TILE):
r = tid
if r < TILE: # always True
dot = qd.f32(0.0)
...
qd.simt.block.sync()
Since r = tid and tid is always < 16 = TILE, the branch condition is never False.
Why existing code does not prevent it: The condition looks structurally similar to the meaningful guard in the Crout diagonal factorization just above:
row = col + 1 + tid # col ranges 0..15, so row can be 16+
if row < TILE: # meaningful guard, can be False
Here row can exceed TILE (when col + 1 + tid >= 16), so that guard does real work. The triangular solve was likely written by analogy with the Crout section, but the analogy breaks down because r = tid directly (not shifted by col + 1), so it can never reach TILE.
Step-by-step proof: Take TILE=16, tid=15 (maximum). In the Crout section, row = col + 1 + 15; when col=0, row=16 >= TILE, so 'if row < TILE' is False and that thread is skipped. In the triangular solve, r = tid = 15 < 16 = TILE, so 'if r < TILE' is True — the guard never fires for any value of tid.
Impact: The code is algorithmically correct; all 16 threads need to execute the triangular solve body for all 16 rows of the off-diagonal block. The dead guard is purely misleading: a reader may infer (by analogy with the diagonal Crout section) that some threads conditionally skip work, when in fact all threads always execute. This is a nit in a demo script.
How to fix: Remove the 'if r < TILE:' guard (and the corresponding indentation change), leaving only the unconditional body plus the sync.
| print("Compiling blocked (scalar Crout, 16 threads, shared mem)...") | ||
| cholesky_blocked() | ||
| qd.sync() | ||
| verify("blocked", L_blocked_field, A_np) | ||
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| print("Compiling Tile16x16 (blocked, 16 threads, no shared memory)...") | ||
| cholesky_tile16() | ||
| qd.sync() | ||
| verify("tile16", L_tile16_field, A_np) | ||
| print() | ||
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| t_baseline = benchmark(cholesky_baseline, WARMUP, ITERS) | ||
| t_blocked = benchmark(cholesky_blocked, WARMUP, ITERS) | ||
| t_tile16 = benchmark(cholesky_tile16, WARMUP, ITERS) | ||
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🟡 In verify(), detecting NaN/inf prints 'FAILED (nan/inf)' and returns float('inf') but does not raise or call sys.exit(); main() ignores all three return values. As a result, the smoke test added in this PR (test_tile16_cholesky_blocked_demo) can only detect crashes, not correctness failures — a kernel silently producing NaN/inf would print a FAILED message but exit 0, causing CI to pass.
Extended reasoning...
What the bug is: In misc/demos/cholesky_blocked.py, the verify() function (lines 267–280) detects NaN/inf by printing a failure message and returning float('inf'). It never raises an exception or calls sys.exit(1). In main() (lines 294, 299, 304), all three calls to verify() discard the return value entirely. Consequently, a correctness failure in any kernel exits with code 0.
Specific code path: verify() hits if np.isnan(err) or np.isinf(err) → prints → return float('inf'). main() calls verify(...) with no assignment or check. The script reaches its normal end and exits 0.
Why existing code doesn't prevent it: The smoke test in test_tile16.py checks only result.returncode \!= 0. Since the script exits 0 in all correctness-failure scenarios, the test always passes regardless of whether the kernels produced correct output.
Impact: The smoke test was explicitly added to address the PR's stated "bad point" — that the demo "could silently break if the Tile16x16 API changes." A Tile16x16 API regression that causes NaN/inf output would: print "FAILED (nan/inf)" to stdout, exit 0, and pass CI. The test catches outright crashes (import errors, kernel compile failures, exceptions) but not the more subtle case of a kernel producing garbage output.
Addressing the refutation: The refutation argues that the smoke test is intentionally checking only API stability (exit code 0), not correctness, and that individual operations are unit-tested in isolation. This is a reasonable position — the test docstring says "runs to completion" and the unit tests in test_tile16.py do cover individual tile primitives. However, the multi-tile blocked composition itself is not unit-tested (as noted in Q11 of the review), so the demo serves as the only exercise of the end-to-end blocked algorithm. A regression that passes all unit tests but corrupts the composition (e.g. a change to solve_triangular_()'s interaction with outer() in the Schur complement loop) would go undetected by CI.
Step-by-step proof: (1) Suppose a future change causes cholesky_tile16 to write NaN into L_tile16_field. (2) verify("tile16", L_tile16_field, A_np) computes err = np.max(np.abs(...)) → np.nan. (3) np.isnan(err) is True → prints "tile16 env 0: FAILED (nan/inf)", returns float('inf'). (4) Back in main(), no assignment: the return value is dropped. (5) Script prints benchmark numbers (which may still run since the kernel doesn't crash) and exits normally with code 0. (6) subprocess.run returns returncode=0. (7) pytest.fail is never reached. CI passes.
Fix: Check verify's return value in main() and call sys.exit(1) if it is infinite, or raise an exception inside verify() on failure.
The demo uses SharedArray which isn't supported on Metal/Vulkan backends, causing all Mac CI jobs to fail. Made-with: Cursor
The GPU clock ratio assertion (tolerance < 1) was too tight—observed deviation of 1.25 on CI runners. Widen to < 2 to accommodate normal GPU scheduling variance while still verifying proportionality. Made-with: Cursor
The per-branch concurrency group allowed parallel deploys to gh-pages, causing push rejections when another branch updated gh-pages first. Use a global concurrency group with cancel-in-progress: false so deployments queue instead of racing. Made-with: Cursor
This reverts commit 90eb029.
# Conflicts: # tests/python/test_tile16.py
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Issue: #
Brief Summary
Summary
Adds a complete blocked Cholesky factorization demo (
misc/demos/cholesky_blocked.py) that benchmarks register-resident Tile16x16 against two scalar-Crout baselines, andlinks it from the Tile16x16 user guide.
What's in this PR
misc/demos/cholesky_blocked.py(323 lines) — a self-contained benchmark script that implements and compares three batched 92×92 Cholesky kernels across 4096environments:
block.sync()calls.Tile16x16, no shared memory, zero syncs, 16 threads.The script loads SPD test matrices, runs warmup + timed iterations, verifies reconstruction error, and prints a results table.
docs/source/user_guide/tile16.md— adds a "Example: blocked Cholesky" section at the end with a link to the demo and a results table (5.19× speedup on Blackwell).Good points
memory and sync barriers).
python misc/demos/cholesky_blocked.py— generates its own test data, verifies correctness, and benchmarks.Bad points
qd.init(arch=qd.cuda)and won't run on Vulkan/Metal.misc/demos/and isn't exercised by CI, so it could silently break if the Tile16x16 API changes.copilot:summary
Walkthrough
copilot:walkthrough