fix: operator precedence bug in pack_ue8m0_to_int assertion (mantissa check always passes)

[kuishou68]

In deep_gemm/utils/math.py, the pack_ue8m0_to_int function has an operator precedence bug that makes the validation assertion ineffective.

Bug

def pack_ue8m0_to_int(x: torch.Tensor):
    assert x.dtype == torch.float and x.size(-1) % 4 == 0
    assert (x.view(torch.int) & ((1 << 23) - 1) == 0).all()  # BUG: wrong precedence

In Python, == has higher precedence than &. So the expression is parsed as:

x.view(torch.int) & (((1 << 23) - 1) == 0)

((1 << 23) - 1) == 0 evaluates to False (which is 0 numerically), then x.view(torch.int) & 0 gives all zeros, and .all() on all zeros returns True.

This means the assertion always passes regardless of whether the mantissa bits are actually zero, so it silently accepts invalid inputs instead of catching them.

Fix

Add parentheses to ensure the AND operation happens before the equality check:

assert ((x.view(torch.int) & ((1 << 23) - 1)) == 0).all()

This correctly checks that all mantissa bits (lower 23 bits) are zero, which is the intended behavior for UE8M0 format values.

[kuishou68]

I've opened PR #310 to fix this issue.