From df2448613e942baaa83d82e84f435bbf00e834c6 Mon Sep 17 00:00:00 2001
From: shugeo <sgazeos@gmail.com>
Date: Tue, 15 Oct 2019 20:00:07 +0300
Subject: [PATCH] Added gamma distribution functions.

---
 libnd4j/include/templatemath.h | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/libnd4j/include/templatemath.h b/libnd4j/include/templatemath.h
index 908323369..2ce8cd338 100644
--- a/libnd4j/include/templatemath.h
+++ b/libnd4j/include/templatemath.h
@@ -733,6 +733,27 @@ namespace nd4j {
             T temp = val1; val1=val2; val2=temp;
 		};
 
+//        template <typename X, typename Z>
+//        math_def inline Z nd4j_gamma(X a) {
+//
+//        }
+		template <typename X, typename Z>
+		math_def inline Z nd4j_igamma(X a, X x) {
+            Z aim = nd4j_pow<X, X, Z>(x, a) / (nd4j_exp<X,Z>(x) * std::tgamma(a));
+            auto sum = Z(0.);
+            auto denom = Z(1.);
+            for (auto i = 0; Z(1./denom) > Z(1.0e-6); i++) {
+                denom *= (a + i);
+                sum += nd4j_pow<X, int>(x, i) / denom;
+            }
+            return aim * sum;
+		}
+
+		template <typename X, typename Z>
+		math_def inline Z nd4j_igammac(X a, X x) {
+		    return Z(1.) - nd4j_igamma<X, Z>(a, x);
+		}
+
 #ifdef __CUDACC__
 		namespace atomics {
 template <typename T>