From 6de585ea01d51c82807588b9cab17710bc326513 Mon Sep 17 00:00:00 2001
From: Luigi Ballabio <luigi.ballabio@gmail.com>
Date: Mon, 16 Sep 2024 10:23:06 +0200
Subject: [PATCH] Avoid interpolation if not needed

---
 ql/indexes/inflationindex.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/ql/indexes/inflationindex.cpp b/ql/indexes/inflationindex.cpp
index 2c4c16c18d..d1bee54991 100644
--- a/ql/indexes/inflationindex.cpp
+++ b/ql/indexes/inflationindex.cpp
@@ -262,7 +262,11 @@ namespace QuantLib {
             QL_REQUIRE(YY0 != Null<Rate>(),
                        "Missing " << name() << " fixing for " << periodStart);
 
-            if (interpolated()) { // NOT ratio, IS interpolated
+            if (!interpolated() || /* degenerate case */ fixingDate == periodStart) {
+
+                return YY0;
+
+            } else {
 
                 Real dp = periodEnd + 1 - periodStart;
                 Real dl = fixingDate - periodStart;
@@ -271,10 +275,6 @@ namespace QuantLib {
                            "Missing " << name() << " fixing for " << periodEnd+1);
                 return YY0 + (YY1 - YY0) * dl / dp;
 
-            } else { // NOT ratio, NOT interpolated
-
-                return YY0;
-
             }
         }
     }