Add inf special cases in C implementation of gamma related functions

pytensor/scalar/c_code/gamma.c

@@ -218,6 +218,11 @@ DEVICE double GammaP (double n, double x)
 {                               /* --- regularized Gamma function P */
   if ((n <= 0) || (x < 0)) return NPY_NAN;  /* check the function arguments */
   if (x <=  0) return 0;        /* treat x = 0 as a special case */
+  if (isinf(n)) {
+    if (isinf(x)) return NPY_NAN;
+    return 0;
+  }
+  if (isinf(x)) return 1;
   if (x < n+1) return _series(n, x) *exp(n *log(x) -x -logGamma(n));
   return 1 -_cfrac(n, x) *exp(n *log(x) -x -logGamma(n));
 }  /* GammaP() */
@@ -228,6 +233,11 @@ DEVICE double GammaQ (double n, double x)
 {                               /* --- regularized Gamma function Q */
   if ((n <= 0) || (x < 0)) return NPY_NAN;  /* check the function arguments */
   if (x <=  0) return 1;        /* treat x = 0 as a special case */
+  if (isinf(n)) {
+    if (isinf(x)) return NPY_NAN;
+    return 1;
+  }
+  if (isinf(x)) return 0;
   if (x < n+1) return 1 -_series(n, x) *exp(n *log(x) -x -logGamma(n));
   return _cfrac(n, x) *exp(n *log(x) -x -logGamma(n));
 }  /* GammaQ() */

pytensor/scalar/math.py

@@ -631,6 +631,13 @@ def __eq__(self, other):
     def __hash__(self):
         return hash(type(self))
 
+    def c_code_cache_version(self):
+        v = super().c_code_cache_version()
+        if v:
+            return (2, *v)
+        else:
+            return v
+
 
 chi2sf = Chi2SF(upgrade_to_float64, name="chi2sf")
 
@@ -677,6 +684,13 @@ def __eq__(self, other):
     def __hash__(self):
         return hash(type(self))
 
+    def c_code_cache_version(self):
+        v = super().c_code_cache_version()
+        if v:
+            return (2, *v)
+        else:
+            return v
+
 
 gammainc = GammaInc(upgrade_to_float, name="gammainc")
 
@@ -723,6 +737,13 @@ def __eq__(self, other):
     def __hash__(self):
         return hash(type(self))
 
+    def c_code_cache_version(self):
+        v = super().c_code_cache_version()
+        if v:
+            return (2, *v)
+        else:
+            return v
+
 
 gammaincc = GammaIncC(upgrade_to_float, name="gammaincc")
 

tests/scalar/test_math.py

@@ -41,6 +41,16 @@ def test_gammainc_nan_c():
     assert np.isnan(test_func(-1, -1))
 
 
+def test_gammainc_inf_c():
+    x1 = pt.dscalar()
+    x2 = pt.dscalar()
+    y = gammainc(x1, x2)
+    test_func = make_function(CLinker().accept(FunctionGraph([x1, x2], [y])))
+    assert np.isclose(test_func(np.inf, 1), sp.gammainc(np.inf, 1))
+    assert np.isclose(test_func(1, np.inf), sp.gammainc(1, np.inf))
+    assert np.isnan(test_func(np.inf, np.inf))
+
+
 def test_gammaincc_python():
     x1 = pt.dscalar()
     x2 = pt.dscalar()
@@ -59,6 +69,16 @@ def test_gammaincc_nan_c():
     assert np.isnan(test_func(-1, -1))
 
 
+def test_gammaincc_inf_c():
+    x1 = pt.dscalar()
+    x2 = pt.dscalar()
+    y = gammaincc(x1, x2)
+    test_func = make_function(CLinker().accept(FunctionGraph([x1, x2], [y])))
+    assert np.isclose(test_func(np.inf, 1), sp.gammaincc(np.inf, 1))
+    assert np.isclose(test_func(1, np.inf), sp.gammaincc(1, np.inf))
+    assert np.isnan(test_func(np.inf, np.inf))
+
+
 def test_gammal_nan_c():
     x1 = pt.dscalar()
     x2 = pt.dscalar()