Gridmask Cpu

[PawelA]

Why we need this PR?

• It adds new feature useful for EfficientDet pipeline

What happened in this PR?

• What solution was applied:
  • Added kernel which performs the gridmask augumentation (https://arxiv.org/abs/2001.04086)
  • Added operator
• Affected modules and functionalities:
  • Self-contained
• Key points relevant for the review:
  • Kernel and operator
• Validation and testing:
  • Added operator test
• Documentation (including examples):
  • Todo

JIRA TASK: NA

[JanuszL]

I wonder what would be the perf gain when C is a template argument and we have a compile time generated variant for 1, 3, 4 and the generic one like here.
@mzient what do you think?

[mzient]

The gain can be significant.

[JanuszL]

!build

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[JanuszL]

!build

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[JanuszL]

CI test failed:

======================================================================
FAIL: test_operator_gridmask.test_cpu_vs_cv_random(<nvidia.dali.backend_impl.TensorCPU object at 0x7f9c1680e068>, <nvidia.dali.backend_impl.TensorCPU object at 0x7f9c1680e110>, 51, 0.38158387, 2.6810782)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/nose/case.py", line 198, in runTest
    self.test(*self.arg)
  File "/opt/dali/dali/test/python/test_operator_gridmask.py", line 90, in check
    assert np.all(result2 == input2)
AssertionError
----------------------------------------------------------------------

Can you check it?

[PawelA]

I managed to reproduce it, the problem seems to be that tile * ratio (the width of black squares) is far from an integer (19.46), which trips up the grid generation (because first it makes an unrotated grid, then it rotates it). I can either improve the grid generation, or choose ratio so that tile * ratio is an integer. What do you think?

[JanuszL]

choose ratio so that tile * ratio is an integer

I don't think we can make such assumption in general. How the paper deals with that (or silently ignores the problem)?

improve the grid generatio

I think that would be the preferable way.

[PawelA]

Improved mask grid generation, but now it's much slower. I don't know how to make it faster with np or cv.

[jantonguirao]

You mentioned in the comment that now the tests are slower. I see that the batch size and number of iterations were doubled, which means the test has 4 times more work to do. If you want to reduce testing time I'd reduce the number of iterations (3 should be enough, I think)

[PawelA]

I did, but then i made them fast again (7f268fd), so I brought back the old parameters. I think the time taken by both tests is fine.

[JanuszL]

It takes 12s, looks good.

[JanuszL]

!build

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