BUG: Enforce high >= low on uniform number generators

Check that high is weakly larger than low and raise if now

closes #17905

4 files changed, 28 insertions, 14 deletions

diff --git a/numpy/random/_generator.pyx b/numpy/random/_generator.pyx
index 7ffa36775..cd951526b 100644
--- a/numpy/random/_generator.pyx
+++ b/numpy/random/_generator.pyx
@@ -859,7 +859,8 @@ cdef class Generator:
             greater than or equal to low.  The default value is 0.
         high : float or array_like of floats
             Upper boundary of the output interval.  All values generated will be
-            less than high.  The default value is 1.0.
+            less than high.  The default value is 1.0. high - low must be
+            non-negative.
         size : int or tuple of ints, optional
             Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
             ``m * n * k`` samples are drawn.  If size is ``None`` (default),
@@ -914,7 +915,7 @@ cdef class Generator:
         """
         cdef bint is_scalar = True
         cdef np.ndarray alow, ahigh, arange
-        cdef double _low, _high, range
+        cdef double _low, _high, rng
         cdef object temp
 
         alow = <np.ndarray>np.PyArray_FROM_OTF(low, np.NPY_DOUBLE, np.NPY_ALIGNED)
@@ -923,13 +924,13 @@ cdef class Generator:
         if np.PyArray_NDIM(alow) == np.PyArray_NDIM(ahigh) == 0:
             _low = PyFloat_AsDouble(low)
             _high = PyFloat_AsDouble(high)
-            range = _high - _low
-            if not np.isfinite(range):
-                raise OverflowError('Range exceeds valid bounds')
+            rng = _high - _low
+            if not np.isfinite(rng):
+                raise OverflowError('high - low range exceeds valid bounds')
 
             return cont(&random_uniform, &self._bitgen, size, self.lock, 2,
                         _low, '', CONS_NONE,
-                        range, '', CONS_NONE,
+                        rng, 'high - low', CONS_NON_NEGATIVE,
                         0.0, '', CONS_NONE,
                         None)
 
@@ -943,7 +944,7 @@ cdef class Generator:
             raise OverflowError('Range exceeds valid bounds')
         return cont(&random_uniform, &self._bitgen, size, self.lock, 2,
                     alow, '', CONS_NONE,
-                    arange, '', CONS_NONE,
+                    arange, 'high - low', CONS_NON_NEGATIVE,
                     0.0, '', CONS_NONE,
                     None)
 
diff --git a/numpy/random/mtrand.pyx b/numpy/random/mtrand.pyx
index d43e7f5aa..7f4fe1c3c 100644
--- a/numpy/random/mtrand.pyx
+++ b/numpy/random/mtrand.pyx
@@ -1026,7 +1026,8 @@ cdef class RandomState:
             greater than or equal to low.  The default value is 0.
         high : float or array_like of floats
             Upper boundary of the output interval.  All values generated will be
-            less than or equal to high.  The default value is 1.0.
+            less than or equal to high.  The default value is 1.0. high - low must be
+            non-negative.
         size : int or tuple of ints, optional
             Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
             ``m * n * k`` samples are drawn.  If size is ``None`` (default),
@@ -1095,7 +1096,7 @@ cdef class RandomState:
         """
         cdef bint is_scalar = True
         cdef np.ndarray alow, ahigh, arange
-        cdef double _low, _high, range
+        cdef double _low, _high, rng
         cdef object temp
 
         alow = <np.ndarray>np.PyArray_FROM_OTF(low, np.NPY_DOUBLE, np.NPY_ALIGNED)
@@ -1104,13 +1105,13 @@ cdef class RandomState:
         if np.PyArray_NDIM(alow) == np.PyArray_NDIM(ahigh) == 0:
             _low = PyFloat_AsDouble(low)
             _high = PyFloat_AsDouble(high)
-            range = _high - _low
-            if not np.isfinite(range):
-                raise OverflowError('Range exceeds valid bounds')
+            rng = _high - _low
+            if not np.isfinite(rng):
+                raise OverflowError('High - low range exceeds valid bounds')
 
             return cont(&random_uniform, &self._bitgen, size, self.lock, 2,
                         _low, '', CONS_NONE,
-                        range, '', CONS_NONE,
+                        rng, 'high - low', CONS_NON_NEGATIVE,
                         0.0, '', CONS_NONE,
                         None)
 
@@ -1123,7 +1124,7 @@ cdef class RandomState:
             raise OverflowError('Range exceeds valid bounds')
         return cont(&random_uniform, &self._bitgen, size, self.lock, 2,
                     alow, '', CONS_NONE,
-                    arange, '', CONS_NONE,
+                    arange, 'high - low', CONS_NON_NEGATIVE,
                     0.0, '', CONS_NONE,
                     None)
 
diff --git a/numpy/random/tests/test_generator_mt19937.py b/numpy/random/tests/test_generator_mt19937.py
index b69cd38d4..4b534fcec 100644
--- a/numpy/random/tests/test_generator_mt19937.py
+++ b/numpy/random/tests/test_generator_mt19937.py
@@ -1666,6 +1666,12 @@ class TestRandomDist:
         # DBL_MAX by increasing fmin a bit
         random.uniform(low=np.nextafter(fmin, 1), high=fmax / 1e17)
 
+    def test_uniform_neg_range(self):
+        func = random.uniform
+        assert_raises(ValueError, func, 2, 1)
+        assert_raises(ValueError, func,  [1, 2], [1, 1])
+        assert_raises(ValueError, func,  [[0, 1],[2, 3]], 2)
+
     def test_scalar_exception_propagation(self):
         # Tests that exceptions are correctly propagated in distributions
         # when called with objects that throw exceptions when converted to
diff --git a/numpy/random/tests/test_random.py b/numpy/random/tests/test_random.py
index c13fc39e3..473ca08e4 100644
--- a/numpy/random/tests/test_random.py
+++ b/numpy/random/tests/test_random.py
@@ -916,6 +916,12 @@ class TestRandomDist:
         # account for i386 extended precision DBL_MAX / 1e17 + DBL_MAX >
         # DBL_MAX by increasing fmin a bit
         np.random.uniform(low=np.nextafter(fmin, 1), high=fmax / 1e17)
+    
+    def test_uniform_neg_range(self):
+        func = np.random.uniform
+        assert_raises(ValueError, func, 2, 1)
+        assert_raises(ValueError, func,  [1, 2], [1, 1])
+        assert_raises(ValueError, func,  [[0, 1],[2, 3]], 2)
 
     def test_scalar_exception_propagation(self):
         # Tests that exceptions are correctly propagated in distributions