__ridx__ is an _undefined name_ in this context but __self.ridx__ is used three other times in this method and nine times in this class. Undefined names may raise [NameError](https://docs.python.org/3/library/exceptions.html#NameError) at runtime.
flake8 testing of https://github.com/opencv/opencv
$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
```
./modules/ts/misc/table_formatter.py:50:23: F821 undefined name 'ridx'
self.rows[ridx + 1].props = properties
^
```
Arm: fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4 (#11409)
* fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4
* avoid the race condition in the reduce
* imgproc(ocl): simplify CLAHE code
* remove unused class
* Issue 11242 intrinsics v_extract, v_rotate improvement, branch 3.4, without C++11 (remove type restrictions for SSE2, use PALIGNR on SSSE3, compile to no-op when imm is 0 or nlanes).
* fix whitespace
* Fix#11242 (NEON intrinsics v_rotate...) branch 3.4
Separate macro expansion OPENCV_HAL_IMPL_NEON_SHIFT_OP for bitwise shifts for integers, from macro expansion OPENCV_HAL_IMPL_NEON_ROTATE for lane rotations. Bitwise shifts do not apply to floats, but lane-rotations can apply to both.
* fix whitespace
* Fix#11242 compile error (VSX intrinsics v_rotate(a)) branch 3.4 no-c++11
* Fix CV_Asserts with negation of strings
{!"string"} causes some compilers to throw a warning.
The value of the string is not that important -- it's only for printing
the assertion message.
Replace these calls with:
CV_Error(Error::StsError, "string")
to suppress the warning.
* remove unnecessary 'break' after CV_Error()
* model is not learned when grabcut is called with GC_EVAL
* fixed test, was writing to wrong file.
* modified patch by Iwan Paolucci; added GC_EVAL_FREEZE_MODEL in addition to GC_EVAL (which semantics is retained)