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cutlass/examples/python/CuTeDSL/dsl_tutorials/dataclass_immutable.py
2026-06-22 22:07:29 -04:00

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"""
Dataclass Example: Passing Tensors via Frozen Dataclass
=======================================================
Demonstrates passing tensors from `@cute.jit` to `@cute.kernel`
using `@dataclass(frozen=True)`.
Uses fake tensors for compilation and TVM-FFI for efficient runtime dispatch.
To run:
.. code-block:: bash
python examples/python/CuTeDSL/cute/dataclass_immutable.py
"""
from dataclasses import dataclass
import cutlass
import cutlass.cute as cute
from cutlass import Int32
@dataclass(frozen=True)
class CopyParams:
"""
Dataclass with one static attribute and two tensors.
Attributes:
num_threads: Threads per block (static - used for loop unrolling)
src: Source tensor (dynamic)
dst: Destination tensor (dynamic)
"""
num_threads: int # static
src: cute.Tensor # dynamic
dst: cute.Tensor # dynamic
@cute.jit
def memcpy_jit(mSrc: cute.Tensor, mDst: cute.Tensor, num_threads: cutlass.Constexpr[int]):
"""Host function - passes tensors via dataclass."""
params = CopyParams(
num_threads=num_threads,
src=mSrc,
dst=mDst,
)
N = mSrc.shape[0]
num_blocks = cute.ceil_div(N, num_threads)
memcpy_kernel(params, N).launch(
grid=[num_blocks, 1, 1],
block=[num_threads, 1, 1],
)
@cute.kernel
def memcpy_kernel(params: CopyParams, N: Int32):
"""Device kernel - receives tensors via CopyParams dataclass."""
tidx, _, _ = cute.arch.thread_idx()
bidx, _, _ = cute.arch.block_idx()
idx = bidx * params.num_threads + tidx
if idx < N:
params.dst[idx] = params.src[idx]
if __name__ == "__main__":
import torch
from cutlass.cute.runtime import make_fake_compact_tensor
n = cute.sym_int64()
# 1. Create fake tensors for compilation (no GPU memory allocated)
fake_src = make_fake_compact_tensor(cutlass.Float32, (n,), stride_order=(0,))
fake_dst = make_fake_compact_tensor(cutlass.Float32, (n,), stride_order=(0,))
# 2. Compile with --enable-tvm-ffi
compiled_fn = cute.compile(
memcpy_jit, fake_src, fake_dst, num_threads=128, options="--enable-tvm-ffi"
)
# 3. Create real torch tensors
src = torch.randn(1024, device="cuda", dtype=torch.float32)
dst = torch.zeros_like(src)
# 4. Run compiled kernel
compiled_fn(src, dst)
# 5. Verify dst == src
torch.cuda.synchronize()
torch.testing.assert_close(dst, src)
print("PASS")