import torch device = torch.device("mps")

1. Incorrectly allows move to MPS

x = torch.randn(2, 2, dtype=torch.cdouble, device="cpu").to(device) print(x.dtype) # torch.complex128 on mps

2. Crash on operation

RuntimeError: Undefined type ComplexDouble

y = x * x

3. Correctly blocks conversion (Inconsistent with above)

TypeError: Trying to convert ComplexDouble to the MPS backend...

z = torch.randn(2, 2, device=device).to(torch.cdouble)

Fix Plan

1. Update PyTorch to the latest version

Ensure you're running the latest version of PyTorch. This issue might be fixed in a newer version.

2. Modify torch.randn to use torch.complex128 directly on the MPS device

import torch
device = torch.device("mps")

# Correct way to create complex128 tensor on MPS
x = torch.randn(2, 2, dtype=torch.complex128, device=device)
print(x.dtype)  # torch.complex128 on mps

# Perform operations on x
y = x * x

3. Update torch.randn to raise a TypeError when moving complex128 to MPS

import torch
device = torch.device("mps")

# Incorrectly allows move to MPS (fix this)
def custom_randn(*args, **kwargs):
    if args[0].dtype == torch.cdouble and device.type == "mps":
        raise TypeError("Cannot move complex128 to MPS")
    return torch.randn(*args, **kwargs)

x = custom_randn(2, 2, dtype=torch.cdouble, device="cpu").to(device)
try:
    print(x.dtype)  # Should raise TypeError
except TypeError as e:
    print(e)

4. Verify the fix

Run the reproduction code again and ensure it raises a TypeError when moving complex128 to MPS.