Simplify implementation of _is_sorted.

anntzer · anntzer · commit ba38186594c6 · 2022-12-02T13:58:14.000+01:00
We don't need a separate specialization for ints (we can rely on the
compiler to inline isnan&lt;int&gt; as always false), and having a separate
loop to find the first non-nan value isn't necessary either.

One change in behavior this causes (in this private function) is that a
fully nan input is considered as being sorted, but this is consistent
with empty inputs being considered sorted too, and also OK with the
actual use of the function (determine whether to go through a fast path
in drawing lines -- fully nan lines are not drawn anyways).
diff --git a/src/_path.h b/src/_path.h
@@ -1244,68 +1244,24 @@ bool convert_to_string(PathIterator &path,
 }
 
 template<class T>
-struct _is_sorted
+bool is_sorted(PyArrayObject *array)
 {
-    bool operator()(PyArrayObject *array)
-    {
-        npy_intp size;
-        npy_intp i;
-        T last_value = -INFINITY;
-        T current_value;
-
-        size = PyArray_DIM(array, 0);
-
-        for (i = 0; i < size; ++i) {
-            last_value = *((T *)PyArray_GETPTR1(array, i));
-            if (!std::isnan(last_value)) {
-                break;
-            }
-        }
-
-        if (i == size) {
-            // The whole array is non-finite
-            return false;
-        }
-
-        for (; i < size; ++i) {
-            current_value = *((T *)PyArray_GETPTR1(array, i));
-            if (!std::isnan(current_value)) {
-                if (current_value < last_value) {
-                    return false;
-                }
-                last_value = current_value;
-            }
-        }
-
-        return true;
-    }
-};
-
-
-template<class T>
-struct _is_sorted_int
-{
-    bool operator()(PyArrayObject *array)
-    {
-        npy_intp size;
-        npy_intp i;
-        T last_value;
-        T current_value;
-
-        size = PyArray_DIM(array, 0);
-
-        last_value = *((T *)PyArray_GETPTR1(array, 0));
-
-        for (i = 1; i < size; ++i) {
-            current_value = *((T *)PyArray_GETPTR1(array, i));
-            if (current_value < last_value) {
+    npy_intp size = PyArray_DIM(array, 0);
+    using limits = std::numeric_limits<T>;
+    T last = limits::has_infinity ? -limits::infinity() : limits::min();
+
+    for (npy_intp i = 0; i < size; ++i) {
+        T current = *(T *)PyArray_GETPTR1(array, i);
+        // The following tests !isnan(current), but also works for integral
+        // types.  (The isnan(IntegralType) overload is absent on MSVC.)
+        if (current == current) {
+            if (current < last) {
                 return false;
             }
-            last_value = current_value;
+            last = current;
         }
-
-        return true;
     }
+    return true;
 };
 
 
diff --git a/src/_path_wrapper.cpp b/src/_path_wrapper.cpp
@@ -807,54 +807,29 @@ static PyObject *Py_is_sorted(PyObject *self, PyObject *obj)
 
     /* Handle just the most common types here, otherwise coerce to
     double */
-    switch(PyArray_TYPE(array)) {
+    switch (PyArray_TYPE(array)) {
     case NPY_INT:
-        {
-            _is_sorted_int<npy_int> is_sorted;
-            result = is_sorted(array);
-        }
+        result = is_sorted<npy_int>(array);
         break;
-
     case NPY_LONG:
-        {
-            _is_sorted_int<npy_long> is_sorted;
-            result = is_sorted(array);
-        }
+        result = is_sorted<npy_long>(array);
         break;
-
     case NPY_LONGLONG:
-        {
-            _is_sorted_int<npy_longlong> is_sorted;
-            result = is_sorted(array);
-        }
+        result = is_sorted<npy_longlong>(array);
         break;
-
     case NPY_FLOAT:
-        {
-            _is_sorted<npy_float> is_sorted;
-            result = is_sorted(array);
-        }
+        result = is_sorted<npy_float>(array);
         break;
-
     case NPY_DOUBLE:
-        {
-            _is_sorted<npy_double> is_sorted;
-            result = is_sorted(array);
-        }
+        result = is_sorted<npy_double>(array);
         break;
-
     default:
-        {
-            Py_DECREF(array);
-            array = (PyArrayObject *)PyArray_FromObject(obj, NPY_DOUBLE, 1, 1);
-
-            if (array == NULL) {
-                return NULL;
-            }
-
-            _is_sorted<npy_double> is_sorted;
-            result = is_sorted(array);
+        Py_DECREF(array);
+        array = (PyArrayObject *)PyArray_FromObject(obj, NPY_DOUBLE, 1, 1);
+        if (array == NULL) {
+            return NULL;
         }
+        result = is_sorted<npy_double>(array);
     }
 
     Py_DECREF(array);
