Fix unary reductions

[magnatelee]

This PR to fix #359 and also make count_nonzero use the same template so that it can support axis.

[magnatelee]

cc @trxcllnt this PR might have some merge conflicts with your ongoing PR if you are working on the C++ code.

[ipdemes]

I know it wasn't in original tests, but could you, maybe, add tests for different array dimension from (up to LEGATE_MAX_DIM)?

[magnatelee]

I know it wasn't in original tests, but could you, maybe, add tests for different array dimension from (up to LEGATE_MAX_DIM)?

dafa481

[manopapad]

This program:

import cunumeric as cn
print(cn.argmax(cn.ones((3,))))

is failing with:

Traceback (most recent call last):
  File "/Users/mpapadakis/legate.core/install/lib/python3.8/site-packages/legion_top.py", line 434, in legion_python_main
    run_path(args[start], run_name='__main__')
  File "/Users/mpapadakis/legate.core/install/lib/python3.8/site-packages/legion_top.py", line 255, in run_path
    exec(code, module.__dict__, module.__dict__)
  File "a.py", line 2, in <module>
    print(cn.argmax(cn.ones((3,))))
  File "/Users/mpapadakis/cunumeric/cunumeric/coverage.py", line 106, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 88, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/module.py", line 4447, in argmax
    return a.argmax(axis=axis, out=out)
  File "/Users/mpapadakis/cunumeric/cunumeric/coverage.py", line 106, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 1569, in argmax
    return self._perform_unary_reduction(
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 3558, in _perform_unary_reduction
    result._thunk.unary_reduction(
  File "/Users/mpapadakis/cunumeric/cunumeric/deferred.py", line 75, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/deferred.py", line 1703, in unary_reduction
    lhs_array.fill(np.array(fill_value, dtype=lhs_array.dtype))
OverflowError: Python int too large to convert to C long

and this:

import cunumeric as cn
print(cn.argmax(cn.array([1,2,3,1])))

is failing with:

Traceback (most recent call last):
  File "/Users/mpapadakis/legate.core/install/lib/python3.8/site-packages/legion_top.py", line 434, in legion_python_main
    run_path(args[start], run_name='__main__')
  File "/Users/mpapadakis/legate.core/install/lib/python3.8/site-packages/legion_top.py", line 255, in run_path
    exec(code, module.__dict__, module.__dict__)
  File "a.py", line 2, in <module>
    print(cn.argmax(cn.array([1,2,3,1])))
  File "/Users/mpapadakis/cunumeric/cunumeric/coverage.py", line 106, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 88, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/module.py", line 4447, in argmax
    return a.argmax(axis=axis, out=out)
  File "/Users/mpapadakis/cunumeric/cunumeric/coverage.py", line 106, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 1569, in argmax
    return self._perform_unary_reduction(
  File "/Users/mpapadakis/cunumeric/cunumeric/array.py", line 3558, in _perform_unary_reduction
    result._thunk.unary_reduction(
  File "/Users/mpapadakis/cunumeric/cunumeric/deferred.py", line 75, in wrapper
    return func(*args, **kwargs)
  File "/Users/mpapadakis/cunumeric/cunumeric/deferred.py", line 1703, in unary_reduction
    lhs_array.fill(np.array(fill_value, dtype=lhs_array.dtype))
  File "/Users/mpapadakis/cunumeric/cunumeric/deferred.py", line 1103, in fill
    assert numpy_array.size == 1
AssertionError

[magnatelee]

@manopapad I think what you reported is a known issue: #87 argmin and argmax currently support only the cases where the output is at least 1-d and an axis is given. #346 is supposed to address it, so let's not fix it in this PR.