Code Contribution: 【Lv1】【Bug Fix】- Fixed the issue where the cat operator would throw an error when the dim is a negative number.

[Bowen12992]

concat (cat) 在运行时，dim 为负数的时候有概率会报错，下面是复现代码，使用注释掉的 torch 的 aten 算子运行不会报错

import flag_gems
import torch

def cat_negative_dim_test():
    x = torch.randn(3, 2, device="cuda")
    y = torch.randn(3, 3, device="cuda")
    return flag_gems.cat((x, y, x), -1)
    # return torch.cat((x, y, x), -1)

y = cat_negative_dim_test()
print(y)

报错如下：

  File "/work/FlagGems/src/flag_gems/ops/cat.py", line 41, in cat
    raise RuntimeError(
RuntimeError: Sizes of tensors must match except in dimension -1. Expected size 2 but got size 3 for tensor number 1 in the list

[Tango2018cc]

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[2niuhe]

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[Tango2018cc]

领取后，请于下周1前完成，谢谢

[2niuhe]

PR: https://github.com/FlagOpen/FlagGems/pull/261