Add scalar rule for loggamma(a, x)

devmotion · devmotion · commit 41f11656128f · 2021-04-07T08:45:19.000+02:00
diff --git a/src/chainrules.jl b/src/chainrules.jl
@@ -114,3 +114,10 @@ ChainRulesCore.@scalar_rule(
 ChainRulesCore.@scalar_rule(logabsgamma(x), digamma(x), ChainRulesCore.Zero())
 
 ChainRulesCore.@scalar_rule(loggamma(x), digamma(x))
+ChainRulesCore.@scalar_rule(
+    loggamma(a, x),
+    (
+        ChainRulesCore.@thunk(error("not implemented")),
+        -exp(- (x + Ω)) * x^(a - 1),
+    )
+)
