NVIDIA / NVIDIA/cutlass

[BUG]strange tv layout for LdMatrix16x16x8bOp

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Description

When building atom copy ldmatrix for 8b element, the layout doesn't seem normal. I expect it to be (32, 16): (16, 1). Since Nvidia haven't released a cuteDSL FP8 Gemm example for blackwell geforce, is it possibly a bug?

a_dtype = cutlass.Int8
atom_copy_ldmatrix_A = cute.make_copy_atom(
    cute.nvgpu.warp.LdMatrix16x16x8bOp(2),
    a_dtype,
)
print(f"copy_atom_op: LdMatrix16x16x8bOp")
print(f"DEBUG: atom_copy_ldmatrix_A: \n {atom_copy_ldmatrix_A}")
--------------------------------
# Output
copy_atom_op: LdMatrix16x16x8bOp
DEBUG: atom_copy_ldmatrix_A: 
 Copy Atom
  ThrID:         32:1
  TV Layout Src: ((2,2,4,2),16):((16,128,32,256),1)
  TV Layout Dst: ((4,8),(1,2,2,4)):((32,1),(1,16,8,128))
  Value type:    i8
Image

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First steps

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Research direction

Start with the shown Python reproduction and the cute.nvgpu.warp.LdMatrix16x16x8bOp entry point. Inspect how the copy atom constructs its source and destination layouts, then compare the printed result with the expected (32, 16):(16, 1) layout. Done means determining whether the output is an implementation bug or an incorrect expectation, with a focused reproduction or fix identified.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp, python
Domain
hpc
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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