jittor.test.test_cudnn_op有时ok有时fail

[LXY666def]

Describe the bug

jittor.test.test_cudnn_op有时ok有时fail，不清楚原因，终端命令可以正常查到安装的cudnn，jittor/pytorch都可以正常训练

Full Log

======================================================================
FAIL: test (main.TestCudnnConvOp)

Traceback (most recent call last):
File "/home/cityofstars/anaconda3/envs/jittor/lib/python3.8/site-packages/jittor/test/test_cudnn_op.py", line 72, in test
check([10,40,50,4], [5,4,5,5], stride=1, padding=1, dilation=1)
File "/home/cityofstars/anaconda3/envs/jittor/lib/python3.8/site-packages/jittor/test/test_cudnn_op.py", line 70, in check
assert np.allclose(y.data, cy.data), np.abs(y.data-cy.data).max()
AssertionError: 0.0039253235

======================================================================
FAIL: test_backward (main.TestCudnnConvOp)

Traceback (most recent call last):
File "/home/cityofstars/anaconda3/envs/jittor/lib/python3.8/site-packages/jittor/test/test_cudnn_op.py", line 130, in test_backward
check([10,4,40,50], [5,4,5,5], stride=1, padding=1, dilation=1)
File "/home/cityofstars/anaconda3/envs/jittor/lib/python3.8/site-packages/jittor/test/test_cudnn_op.py", line 125, in check
assert np.allclose(y.data, cy.data)
AssertionError

---

Ran 5 tests in 1.407s

FAILED (failures=2)

Minimal Reproduce

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Expected behavior

test应该一直是ok才对