Merge pull request #9577 from bashtage/dirichlet-alpha-validation

BUG: Missing dirichlet input validation

2 files changed, 12 insertions, 0 deletions

diff --git a/numpy/random/mtrand/mtrand.pyx b/numpy/random/mtrand/mtrand.pyx
index 68905f7ad..c4b4f7748 100644
--- a/numpy/random/mtrand/mtrand.pyx
+++ b/numpy/random/mtrand/mtrand.pyx
@@ -4666,6 +4666,11 @@ cdef class RandomState:
         samples : ndarray,
             The drawn samples, of shape (size, alpha.ndim).
 
+        Raises
+        -------
+        ValueError
+            If any value in alpha is less than or equal to zero
+
         Notes
         -----
         .. math:: X \\approx \\prod_{i=1}^{k}{x^{\\alpha_i-1}_i}
@@ -4731,6 +4736,8 @@ cdef class RandomState:
 
         k           = len(alpha)
         alpha_arr   = <ndarray>PyArray_ContiguousFromObject(alpha, NPY_DOUBLE, 1, 1)
+        if np.any(np.less_equal(alpha_arr, 0)):
+            raise ValueError('alpha <= 0')
         alpha_data  = <double*>PyArray_DATA(alpha_arr)
 
         shape = _shape_from_size(size, k)
diff --git a/numpy/random/tests/test_random.py b/numpy/random/tests/test_random.py
index 3a1d8af51..39c45889f 100644
--- a/numpy/random/tests/test_random.py
+++ b/numpy/random/tests/test_random.py
@@ -525,6 +525,11 @@ class TestRandomDist(object):
 
         assert_raises(TypeError, np.random.dirichlet, p, float(1))
 
+    def test_dirichlet_bad_alpha(self):
+        # gh-2089
+        alpha = np.array([5.4e-01, -1.0e-16])
+        assert_raises(ValueError, np.random.mtrand.dirichlet, alpha)
+
     def test_exponential(self):
         np.random.seed(self.seed)
         actual = np.random.exponential(1.1234, size=(3, 2))