From b9b24ab0398f01269282d81ce7a2bfa1929e18cc Mon Sep 17 00:00:00 2001
From: "Hugo U. R. Strand" <hugo.strand@gmail.com>
Date: Tue, 3 Nov 2026 14:14:51 +0100
Subject: [PATCH] [imtime] reuse Hilbert transforms in convolution

---
 c++/cppdlr/dlr_imtime.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/c++/cppdlr/dlr_imtime.hpp b/c++/cppdlr/dlr_imtime.hpp
index 29884c8..d0989b9 100644
--- a/c++/cppdlr/dlr_imtime.hpp
+++ b/c++/cppdlr/dlr_imtime.hpp
@@ -343,8 +343,10 @@ namespace cppdlr {
         auto h = arraymult(tcf2it_v, tmp);
 
         // Off-diagonal contribution
+        auto hfc = arraymult(hilb_v, fc);
+        auto hgc = arraymult(hilb_v, gc);
         for (int i = 0; i < r; ++i) {
-          tmp(i, _, _) = matmul(arraymult(hilb_v, fc)(i, _, _), gc(i, _, _)) + matmul(fc(i, _, _), arraymult(hilb_v, gc)(i, _, _));
+          tmp(i, _, _) = matmul(hfc(i, _, _), gc(i, _, _)) + matmul(fc(i, _, _), hgc(i, _, _));
         }
 
         return beta * (h + arraymult(cf2it, tmp));