DOC, TST, BUG: Improve uint64 core/algos behavior

1) duplicated()

Updates documentation to describe the "values"
parameter in the signature, adds tests for uint64,
and refactors to use duplicated_uint64.

2) mode()

Updates documentation to describe the "values"
parameter in the signature, adds tests for uint64,
and reactors to use mode_uint64.

3) unique()

Uses UInt64HashTable to patch a uint64 overflow bug
analogous to that seen in Series.unique (patched in
pandas-devgh-14915).

4) Types API

Introduces "is_signed_integer_dtype" and "is_unsigned
_integer_dtype" to the public API. Used in refactoring/
patching of 1-3.

doc/source/whatsnew/v0.20.0.txt

@@ -298,5 +298,6 @@ Bug Fixes
 
 
 - Bug in ``Series.unique()`` in which unsigned 64-bit integers were causing overflow (:issue:`14721`)
+- Bug in ``pd.unique()`` in which unsigned 64-bit integers were causing overflow (:issue:`14915`)
 - Require at least 0.23 version of cython to avoid problems with character encodings (:issue:`14699`)
 - Bug in converting object elements of array-like objects to unsigned 64-bit integers (:issue:`4471`)

pandas/api/tests/test_api.py

@@ -153,10 +153,10 @@ class TestTypes(Base, tm.TestCase):
                'is_floating_dtype', 'is_int64_dtype', 'is_integer',
                'is_integer_dtype', 'is_number', 'is_numeric_dtype',
                'is_object_dtype', 'is_scalar', 'is_sparse',
-               'is_string_dtype',
+               'is_string_dtype', 'is_signed_integer_dtype',
                'is_timedelta64_dtype', 'is_timedelta64_ns_dtype',
-               'is_period', 'is_period_dtype',
-               'is_re', 'is_re_compilable',
+               'is_unsigned_integer_dtype', 'is_period',
+               'is_period_dtype', 'is_re', 'is_re_compilable',
                'is_dict_like', 'is_iterator',
                'is_list_like', 'is_hashable',
                'is_named_tuple', 'is_sequence',

pandas/core/algorithms.py

@@ -9,7 +9,9 @@
 from pandas import compat, lib, tslib, _np_version_under1p8
 from pandas.types.cast import _maybe_promote
 from pandas.types.generic import ABCSeries, ABCIndex
-from pandas.types.common import (is_integer_dtype,
+from pandas.types.common import (is_unsigned_integer_dtype,
+                                 is_signed_integer_dtype,
+                                 is_integer_dtype,
                                  is_int64_dtype,
                                  is_categorical_dtype,
                                  is_extension_type,
@@ -490,12 +492,14 @@ def _value_counts_arraylike(values, dropna=True):
 
 def duplicated(values, keep='first'):
     """
-    Return boolean ndarray denoting duplicate values
+    Return boolean ndarray denoting duplicate values.
 
     .. versionadded:: 0.19.0
 
     Parameters
     ----------
+    values : ndarray-like
+        Array over which to check for duplicate values.
     keep : {'first', 'last', False}, default 'first'
         - ``first`` : Mark duplicates as ``True`` except for the first
           occurrence.
@@ -521,9 +525,12 @@ def duplicated(values, keep='first'):
     elif isinstance(values, (ABCSeries, ABCIndex)):
         values = values.values
 
-    if is_integer_dtype(dtype):
+    if is_signed_integer_dtype(dtype):
         values = _ensure_int64(values)
         duplicated = htable.duplicated_int64(values, keep=keep)
+    elif is_unsigned_integer_dtype(dtype):
+        values = _ensure_uint64(values)
+        duplicated = htable.duplicated_uint64(values, keep=keep)
     elif is_float_dtype(dtype):
         values = _ensure_float64(values)
         duplicated = htable.duplicated_float64(values, keep=keep)
@@ -535,7 +542,19 @@ def duplicated(values, keep='first'):
 
 
 def mode(values):
-    """Returns the mode or mode(s) of the passed Series or ndarray (sorted)"""
+    """
+    Returns the mode(s) of an array.
+
+    Parameters
+    ----------
+    values : array-like
+        Array over which to check for duplicate values.
+
+    Returns
+    -------
+    mode : Series
+    """
+
     # must sort because hash order isn't necessarily defined.
     from pandas.core.series import Series
 
@@ -547,10 +566,12 @@ def mode(values):
         constructor = Series
 
     dtype = values.dtype
-    if is_integer_dtype(values):
+    if is_signed_integer_dtype(values):
         values = _ensure_int64(values)
         result = constructor(sorted(htable.mode_int64(values)), dtype=dtype)
-
+    elif is_unsigned_integer_dtype(values):
+        values = _ensure_uint64(values)
+        result = constructor(sorted(htable.mode_uint64(values)), dtype=dtype)
     elif issubclass(values.dtype.type, (np.datetime64, np.timedelta64)):
         dtype = values.dtype
         values = values.view(np.int64)
@@ -893,8 +914,10 @@ def _hashtable_algo(f, values, return_dtype=None):
     dtype = values.dtype
     if is_float_dtype(dtype):
         return f(htable.Float64HashTable, _ensure_float64)
-    elif is_integer_dtype(dtype):
+    elif is_signed_integer_dtype(dtype):
         return f(htable.Int64HashTable, _ensure_int64)
+    elif is_unsigned_integer_dtype(dtype):
+        return f(htable.UInt64HashTable, _ensure_uint64)
     elif is_datetime64_dtype(dtype):
         return_dtype = return_dtype or 'M8[ns]'
         return f(htable.Int64HashTable, _ensure_int64).view(return_dtype)

pandas/hashtable.pyx

@@ -167,73 +167,6 @@ cpdef value_count_object(ndarray[object] values,
     return result_keys, result_counts
 
 
-@cython.wraparound(False)
-@cython.boundscheck(False)
-def mode_object(ndarray[object] values, ndarray[uint8_t, cast=True] mask):
-    cdef:
-        int count, max_count = 2
-        int j = -1 # so you can do +=
-        int k
-        ndarray[object] modes
-        kh_pymap_t *table
-
-    table = kh_init_pymap()
-    build_count_table_object(values, mask, table)
-
-    modes = np.empty(table.n_buckets, dtype=np.object_)
-    for k in range(table.n_buckets):
-        if kh_exist_pymap(table, k):
-            count = table.vals[k]
-
-            if count == max_count:
-                j += 1
-            elif count > max_count:
-                max_count = count
-                j = 0
-            else:
-                continue
-            modes[j] = <object> table.keys[k]
-
-    kh_destroy_pymap(table)
-
-    return modes[:j + 1]
-
-
-@cython.wraparound(False)
-@cython.boundscheck(False)
-def mode_int64(int64_t[:] values):
-    cdef:
-        int count, max_count = 2
-        int j = -1 # so you can do +=
-        int k
-        kh_int64_t *table
-        ndarray[int64_t] modes
-
-    table = kh_init_int64()
-
-    build_count_table_int64(values, table, 0)
-
-    modes = np.empty(table.n_buckets, dtype=np.int64)
-
-    with nogil:
-        for k in range(table.n_buckets):
-            if kh_exist_int64(table, k):
-                count = table.vals[k]
-
-                if count == max_count:
-                    j += 1
-                elif count > max_count:
-                    max_count = count
-                    j = 0
-                else:
-                    continue
-                modes[j] = table.keys[k]
-
-    kh_destroy_int64(table)
-
-    return modes[:j + 1]
-
-
 @cython.wraparound(False)
 @cython.boundscheck(False)
 def duplicated_object(ndarray[object] values, object keep='first'):

pandas/src/hashtable_func_helper.pxi.in

@@ -112,3 +112,85 @@ def duplicated_{{dtype}}({{dtype}}_t[:] values,
     return out
 
 {{endfor}}
+
+#----------------------------------------------------------------------
+# Mode Computations
+#----------------------------------------------------------------------
+
+{{py:
+
+# dtype, ctype, table_type, npy_dtype
+dtypes = [('int64', 'int64_t', 'int64', 'int64'),
+          ('uint64', 'uint64_t', 'uint64', 'uint64'),
+          ('object', 'object', 'pymap', 'object_')]
+}}
+
+{{for dtype, ctype, table_type, npy_dtype in dtypes}}
+
+
+@cython.wraparound(False)
+@cython.boundscheck(False)
+
+{{if dtype == 'object'}}
+
+
+def mode_{{dtype}}(ndarray[{{ctype}}] values,
+                   ndarray[uint8_t, cast=True] mask):
+{{else}}
+
+
+def mode_{{dtype}}({{ctype}}[:] values):
+{{endif}}
+    cdef:
+        int count, max_count = 2
+        int j = -1 # so you can do +=
+        int k
+        kh_{{table_type}}_t *table
+        ndarray[{{ctype}}] modes
+
+    table = kh_init_{{table_type}}()
+
+    {{if dtype == 'object'}}
+    build_count_table_{{dtype}}(values, mask, table)
+    {{else}}
+    build_count_table_{{dtype}}(values, table, 0)
+    {{endif}}
+
+    modes = np.empty(table.n_buckets, dtype=np.{{npy_dtype}})
+
+    {{if dtype != 'object'}}
+    with nogil:
+        for k in range(table.n_buckets):
+            if kh_exist_{{table_type}}(table, k):
+                count = table.vals[k]
+
+                if count == max_count:
+                    j += 1
+                elif count > max_count:
+                    max_count = count
+                    j = 0
+                else:
+                    continue
+
+                modes[j] = table.keys[k]
+    {{else}}
+    for k in range(table.n_buckets):
+        if kh_exist_{{table_type}}(table, k):
+            count = table.vals[k]
+
+            if count == max_count:
+                j += 1
+            elif count > max_count:
+                max_count = count
+                j = 0
+            else:
+                continue
+
+            modes[j] = <object> table.keys[k]
+    {{endif}}
+
+    kh_destroy_{{table_type}}(table)
+
+    return modes[:j + 1]
+
+{{endfor}}