From 9f311fd65b3f9bf8fbc23f669dbd07b6536d156d Mon Sep 17 00:00:00 2001
From: Mykola Lukashchuk <nikola.lukashuk@gmail.com>
Date: Thu, 24 Oct 2024 13:56:37 +0200
Subject: [PATCH] fix: add prod between inverse wisharts

---
 src/distributions/wishart_inverse.jl        |  6 ++++++
 test/distributions/wishart_inverse_tests.jl | 15 ++++++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/distributions/wishart_inverse.jl b/src/distributions/wishart_inverse.jl
index 676c9b0c..6c308999 100644
--- a/src/distributions/wishart_inverse.jl
+++ b/src/distributions/wishart_inverse.jl
@@ -231,6 +231,12 @@ function BayesBase.prod(::PreserveTypeProd{Distribution}, left::InverseWishart,
     return prod(PreserveTypeProd(Distribution), convert(InverseWishartFast, left), right)
 end
 
+BayesBase.default_prod_rule(::Type{<:InverseWishart}, ::Type{<:InverseWishart}) = PreserveTypeProd(Distribution)
+
+function BayesBase.prod(::PreserveTypeProd{Distribution}, left::InverseWishart, right::InverseWishart)
+    return prod(PreserveTypeProd(Distribution), convert(InverseWishartFast, left), convert(InverseWishartFast, right))
+end
+
 function BayesBase.insupport(ef::ExponentialFamilyDistribution{InverseWishartFast}, x::Matrix)
     return size(getindex(unpack_parameters(ef), 2)) == size(x) && isposdef(x)
 end
diff --git a/test/distributions/wishart_inverse_tests.jl b/test/distributions/wishart_inverse_tests.jl
index 7f6ffcc6..3c586004 100644
--- a/test/distributions/wishart_inverse_tests.jl
+++ b/test/distributions/wishart_inverse_tests.jl
@@ -236,10 +236,10 @@ end
     import Distributions: InverseWishart
 
     for Sleft in rand(InverseWishart(10, Array(Eye(2))), 2), Sright in rand(InverseWishart(10, Array(Eye(2))), 2), νright in (6, 7), νleft in (4, 5)
-        let left = InverseWishart(νleft, Sleft), right = InverseWishartFast(νright, Sright)
+        let left = InverseWishart(νleft, Sleft), right = InverseWishart(νleft, Sleft), right_fast = convert(InverseWishartFast, right)
             # Test commutativity of the product
-            prod_result1 = prod(PreserveTypeProd(Distribution), left, right)
-            prod_result2 = prod(PreserveTypeProd(Distribution), right, left)
+            prod_result1 = prod(PreserveTypeProd(Distribution), left, right_fast)
+            prod_result2 = prod(PreserveTypeProd(Distribution), right_fast, left)
             
             @test prod_result1.ν ≈ prod_result2.ν
             @test prod_result1.S ≈ prod_result2.S
@@ -248,12 +248,17 @@ end
             @test prod_result1 isa InverseWishartFast
             @test prod_result2 isa InverseWishartFast
 
-            # prod prod stays if we convert fisrt and then do product
+            # prod stays if we convert fisrt and then do product
             left_fast = convert(InverseWishartFast, left)
-            prod_fast = prod(ClosedProd(), left_fast, right)
+            prod_fast = prod(ClosedProd(), left_fast, right_fast)
 
             @test prod_fast.ν ≈ prod_result1.ν
             @test prod_fast.S ≈ prod_result2.S
+
+            # prod for Inverse Wishart is defenied 
+            prod_result_not_fast = prod(PreserveTypeProd(Distribution), left, right)
+            @test prod_result_not_fast.ν ≈ prod_result1.ν
+            @test prod_result_not_fast.S ≈ prod_result1.S
         end
     end
 end