cuTile → Triton Conversion

cuTile → Triton Conversion

Convert @ct.kernel kernels to @triton.jit. API mapping: references/​api-mapping.md (cuTile → Triton).

In this skill’s Markdown, Triton launch syntax kernel［grid］(…) uses Unicode brackets so link checkers do not parse [grid](…) as a hyperlink; use normal ASCII brackets in real Triton code.

Instructions

Follow the phase-gated workflow in translations/​workflow.md. Every conversion should go through analyze → convert → validate → test → benchmark, with explicit gates before moving on. Use the documents in Workflow Selection when the task matches a special case (errors, layout flags, perf).

1. Optimization strategy (perf-sensitive / attention) — If the op is attention, FMHA, sliding window, soft cap, or GQA (e.g. Gemma gemma_attention), read references/​optimization-strategy.md before converting the inner loop, then apply §4 Gemma FMHA checklist. For other GEMM/​BMM/​attention-adjacent kernels, still skim §2–§3 of that file after TMA is done.

2. Select path — Existing TileGym op: standard mode in translations/​workflow.md. If the cuTile source uses transpose / transpose_v, dual layouts, or MLA-style paths, read translations/​advanced-patterns.md before writing Triton (two kernels + META grid, not one kernel + tl.trans).

3. Pre-flight — Run the Pre-flight Analysis grep commands on the cuTile source. Count @ct.kernel definitions; note TMA-relevant ct.load/ct.store, ct.launch, Constant, and layout flags.

4. Read mapping — Keep references/​api-mapping.md open for cuTile → Triton API pairs. For runtime failures (illegal address, dtype, strides), use references/​debugging.md.

5. Convert — Copy the Conversion Checklist into a todo list and execute in order. Structure and file placement: translations/​file-structure.md. Mandatory: any 2D+ block-shaped tile load/​store uses tl.make_tensor_descriptor (TMA), not raw tl.load(ptr+offs, mask=…) for full tiles—skipping this is the most common source of large regressions. Host side: Triton bracket launch <code>kernel［grid］(args)</​code> with tuple or lambda META: (…) for autotune; no ct.launch.

6. Validate — Syntax-check the new Triton module; run the relevant TileGym pytest targets for the op: pytest tests/​ops/​test_<op>.py -k "triton" -vs. Fix failures before benchmarking.

7. Benchmark — Compare Triton vs cuTile on perf tests. If Triton is clearly slower, follow PERFORMANCE ANALYSIS (Phase c2t-5) in translations/​workflow.md and references/​optimizing-reference.md for GEMM/​BMM/​attention; use references/​optimization-strategy.md as the ordered checklist. If you see 10–50× slowdowns, read CRITICAL PERFORMANCE PATTERNS in that same workflow file first.

Execution rules (MUST):

• Create and track the conversion checklist (e.g. TodoWrite) before editing kernel code; complete steps in order—do not skip pre-flight or TMA decisions.
• For attention / FMHA / Gemma / GQA / soft cap / sliding window: read references/​optimization-strategy.md and apply §4 before treating the conversion as optimized.
• Do not ship raw pointer+mask 2D+ tile loads where TMA applies; document any intentional exception.
• If tests or benchmarks fail a gate, stop and fix before declaring the conversion done—do not stack unverified changes.

Workflow Selection

• Existing TileGym op → Standard Mode: translations/​workflow.md
• Errors (cudaErrorIllegalAddress, shape mismatch, numerical mismatch) → references/​debugging.md
• Advanced patterns (TMA, dual layout flags transpose, autotune + META grid, Array.slice, ct.gather().item()) → translations/​advanced-patterns.md (MLA-style two kernels, avoid 3–15× regression on transpose=False).
• Performance (Triton kernel slower than cuTile, autotuning, profiling) → translations/​workflow.md (section PERFORMANCE ANALYSIS (Phase c2t-5))
• Optimization strategy hub (ordered checklist: advanced-patterns + optimizing-reference) → references/​optimization-strategy.md — read first for attention/​FMHA/​Gemma; then drill into the two source docs as needed
• Optimizing GEMM/​BMM/​attention (after TMA, or Triton 10–20% slower) → references/​optimizing-reference.md — EVEN_K fast path, transpose via pointer arithmetic, grid layout, autotune breadth, epilogue subtile; use these patterns during conversion and before perf sign-off (summarized in optimization-strategy §2–§3)
• Gemma attention / GQA FMHA conversion → references/​optimization-strategy.md §4
• Blackwell optimization (complex kernels with iterative algorithms, register pressure, loop unrolling) → references/​optimizing-reference.md §9 — TMA descriptors, loop_unroll_factor, occupancy autotuning, TMEM-friendly block sizes, slab allocator, dual-path kernel design
• ⚠️ 10-50x REGRESSION (catastrophic slowdown after conversion) → translations/​workflow.md — section CRITICAL PERFORMANCE PATTERNS (AVOID 10-50x REGRESSION)
• ⚠️ Good perf on transpose=True only, collapse on transpose=False (or opposite) → translations/​advanced-patterns.md — §1 Dual layout flag; two @triton.jit kernels + grid = lambda META: (... META["BLOCK_H"] ...)

Pre-flight Analysis (Run BEFORE converting)

# Count kernels (only main kernel gets @triton.jit, helpers stay plain def)
grep "@ct\.kernel" source.py | wc -l

# Check for patterns needing special handling
grep "ct\.transpose\|ct\.permute" source.py   # → use tl.trans/​tl.permute
grep "ct\.astype" source.py                    # → use .to(dtype)
grep "ct\.load\|ct\.store" source.py          # → TMA for 2D+ (tl.make_tensor_descriptor), NOT raw tl.load(ptr+offs)
grep "ct\.launch" source.py                    # → bracket launch: kernel then [grid] then (args)
grep "ct\.Constant\|ct\.ConstInt" source.py    # → tl.constexpr
grep "ct\.cdiv" source.py                      # → triton.cdiv (host) or Python (a+b-1)//b
grep "ct\.bid\|ct\.num_blocks" source.py       # → tl.program_id/​tl.num_programs
grep "1 << .*\.bit_length" source.py           # → triton.next_power_of_2 if needed
grep "transpose\|transpose_v" source.py       # → if hit, read translations/​advanced-patterns.md (dual kernels + META grid)

Conversion Checklist

Copy this checklist and track progress:

Conversion Progress:
 [ ] Step 0 (attention / Gemma FMHA / GQA / soft cap / sliding window): Read [references/​optimization-strategy.md](./​references/​optimization-strategy.md) and apply §4 checklist before inner-loop Triton
 [ ] Step 1: Pre-flight — run grep commands above, note special patterns and 2D+ loads (→ TMA)
 [ ] Step 2: Analyze source cuTile kernel (identify patterns, shapes, dtypes)
 [ ] Step 3: Create Triton file with correct structure (see translations/​file-structure.md)
 [ ] Step 4: Convert kernel signature (tensor args → pointer args, Constant → constexpr)
 [ ] Step 4b: TMA (MANDATORY for 2D+ loads) — use tl.make_tensor_descriptor for every 2D+ tile load/​store; do NOT ship raw tl.load(ptr+offs,mask) for block-shaped access (see workflow.md § TMA OPTIMIZATION)
 [ ] Step 5: Convert kernel body (apply gotchas table below + API mapping)
 [ ] Step 6: Convert host wrapper (grid tuple/​lambda, bracket-style launch: kernel, grid, then arguments; no ct.launch); call triton.set_allocator(alloc_fn) if using TMA
 [ ] Step 7: Validate — run pytest or syntax check on Triton file
 [ ] Step 8: Test — run pytest, verify X passed 0 failed
 [ ] Step 9: If test fails → fix → re-validate → re-test (loop until green)
 [ ] Step 10: Benchmark — run perf test, compare vs cuTile (see workflow.md § PERFORMANCE ANALYSIS)
 [ ] Step 10b: If GEMM/​BMM/​attention and Triton >20% slower → walk [references/​optimization-strategy.md](./​references/​optimization-strategy.md) §2–§3 then [references/​optimizing-reference.md](./​references/​optimizing-reference.md) (EVEN_K, transpose, grid, autotune, epilogue subtile), then re-benchmark
 [ ] Step 10c: If op has `transpose` / layout flag → read [translations/​advanced-patterns.md](./​translations/​advanced-patterns.md); verify **separate kernels** per layout (not transpose-kernel + `tl.trans`); **autotuned** launches use `lambda META: (triton.cdiv(..., META["BLOCK_H"]), ...)` — no fixed `BLOCK_H`/`BLOCK_N` through `apply()` unless autotune is disabled

Post-conversion Verification (TMA is mandatory for 2D+ loads):
 [ ] TMA: All 2D+ tile loads use tl.make_tensor_descriptor(...).load([...]); no raw ptr+mask for block-shaped 2D+ access (else 5x-20x regression)
 [ ] Grid uses tuple or lambda (not 3-tuple required like cuTile)
 [ ] Triton autotune added if cuTile op used kernel_configs/​autotune (see workflow § PERFORMANCE ANALYSIS)
 [ ] Host grid uses triton.cdiv where appropriate (not (a+b-1)//b only)
 [ ] Pointer/​offset indexing: Triton uses element offsets (ptr + offs), not block index in tl.load (or use TMA descriptor)
 [ ] ct.astype(x, dtype) → x.to(dtype) in Triton
 [ ] ct.mma(a, b, acc=acc) → tl.dot(a, b, acc) (no keyword in Triton)
 [ ] Optional/​None args: Triton allows None in kernel args if desired (cuTile required dummy+flag)
 [ ] Masking applied when BLOCK_SIZE > actual dimension (same as cuTile); with TMA, masks can often be removed for full tiles
 [ ] Reduction divisor uses actual_size, NOT BLOCK_SIZE
 [ ] fp32/​tf32: Triton defaults allow_tf32=True; match cuTile behavior if you had explicit tf32 cast
 [ ] If any 2D+ load uses raw ptr+mask (exception only): document WHY TMA was not used
 [ ] tl.assume() alignment hints added for strides and pointers

Gotchas (Most Common Translation Errors) {#gotchas-most-common-translation-errors}

Comprehensive table of patterns that frequently break or regress when porting @ct.kernel to @triton.jit — mma accumulator, type cast, grid, TMA usage, dtype handling, layout flags, batched matmul, etc.

See: references/​gotchas.md — read this BEFORE writing the Triton kernel.

Performance Gotchas (10-50x Regression Risk) {#performance-gotchas-10-50x-regression-risk}

⚠️ These cause CATASTROPHIC slowdowns. Check BEFORE benchmarking.

Patterns and their impact: TMA vs raw ptr+mask (5-20×), autotune vs fixed tile sizes (2-3×), broadcast_to + tl.dot (10-50×), extract_slice chains (2-5×), and more.

See: references/​performance-gotchas.md — full regression-risk table.

Full details: translations/​workflow.md — section CRITICAL PERFORMANCE PATTERNS (AVOID 10-50x REGRESSION).

Full API mapping: references/​api-mapping.md.

Triton math dtype (erf/​erfc/​exp/​log/​sqrt) and the "don't substitute erf with tanh" pattern: references/​debugging.md — section Triton Math Function Dtype Requirements (CRITICAL).

Optimization strategy (hub)

File: references/​optimization-strategy.md

Summarizes translations/​advanced-patterns.md (layout flags, dual kernels, autotune+META, batched launch, Blackwell pointers) and references/​optimizing-reference.md (post-TMA micro-opts, §9) into §1–§3 plus a mandatory §4 Gemma FMHA checklist.

Rule: For attention / FMHA / Gemma-style conversions, open optimization-strategy in the same session as workflow — do not rely on TMA alone for perf sign-off.

Reference Documents {#reference-documents}

Read from cuTile → Triton perspective. Core files live in this skill under ``.

Worked Examples

Use cutile_kernel.py as source and triton_kernel.py as target:

Read cutile_kernel.py first, then triton_kernel.py, to see the inverse mapping.

⚠️ MANDATORY COMPLETION CHECKLIST (DO NOT SKIP)

A conversion is NOT COMPLETE until ALL items are checked. Copy and complete:

MANDATORY COMPLETION GATES:
 [ ] 1. CORRECTNESS: pytest passes with 0 failures
     Command: python -m pytest {test_path} -k "test_op and triton" -vs --tb=short
     Gate: "X passed, 0 failed"

 [ ] 2. TMA OPTIMIZATION: All 2D+ tile loads use tl.make_tensor_descriptor
     Verify: grep -n "tl.load.*mask" triton_file.py | wc -l  # Should be 0 for 2D+ ops
     Skip = 5-20x performance regression

 [ ] 3. PERFORMANCE TEST: Triton within 20% of cuTile baseline
     Command: python -m pytest {test_path} -k "test_perf" --print-record -v
     OR: Run benchmark script: cd tests/​benchmark && python bench_{op}.py
     Gate: Triton TFLOPS >= 0.8 * CuTile TFLOPS

 [ ] 4. PERFORMANCE COMPARISON RECORDED:
     Document results:
     | Config | Triton (TFLOPS) | CuTile (TFLOPS) | Ratio |
     |--------|-----------------|-----------------|-------|
     | [fill] | [fill]          | [fill]          | [fill]|

CONVERSION COMPLETE: All 4 gates passed? → YES / NO

Why this matters:

• Gate 1 catches functional bugs
• Gate 2 prevents catastrophic 5-20x regressions (most common mistake)
• Gate 3 validates that optimization was effective
• Gate 4 creates accountability record

If any gate fails: Fix and re-verify before declaring complete.