From 8de0d12083c904eded759d590b879a501672d3c6 Mon Sep 17 00:00:00 2001
From: yrasool <111371895+yrasool@users.noreply.github.com>
Date: Mon, 22 Jun 2026 14:44:37 -0400
Subject: [PATCH] Fix mergeMctals with many input files

---
 libmcnptools/src/mergeMctals.cpp              |  6 ++++--
 libmcnptools/tests/mctal/tests/CMakeLists.txt |  1 +
 .../mctal/tests/MctalMergeManyInputs.cpp      | 21 +++++++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 libmcnptools/tests/mctal/tests/MctalMergeManyInputs.cpp

diff --git a/libmcnptools/src/mergeMctals.cpp b/libmcnptools/src/mergeMctals.cpp
index 3e674e0..88d2715 100644
--- a/libmcnptools/src/mergeMctals.cpp
+++ b/libmcnptools/src/mergeMctals.cpp
@@ -25,10 +25,11 @@ Mctal mergeMctals(const std::string& name, const std::vector<std::string> mctal_
   Mctal base(mctal_names.at(0));
 
   std::vector<Mctal> mctals;
+  mctals.reserve(mctal_names.size() - 1);
   for(unsigned int m=1; m<mctal_names.size(); m++) {
     if( verbosity > 1 )
       std::cerr << "Indexing MCTAL file \'" << mctal_names.at(m) << "\'" << std::endl;
-    mctals.push_back(Mctal(mctal_names.at(m)));
+    mctals.emplace_back(mctal_names.at(m));
   }
 
   const std::vector<int> tallies = base.GetTallyList();
@@ -137,10 +138,11 @@ Mctal parallelMergeMctals(const std::string& name, const std::vector<std::string
     Mctal base(mctal_names.at(lrank));
 
     std::vector<Mctal> mctals;
+    mctals.reserve(mctal_names.size() / size + 1);
     for(size_t m=lrank+size; m<mctal_names.size(); m+=size) {
       if( verbosity > 1 )
         std::cerr << "Task " << lrank << " indexing MCTAL file \'" << mctal_names.at(m) << "\'" << std::endl;
-      mctals.push_back(Mctal(mctal_names.at(m)));
+      mctals.emplace_back(mctal_names.at(m));
     }
 
     // build the total number of histories and random numbers used
diff --git a/libmcnptools/tests/mctal/tests/CMakeLists.txt b/libmcnptools/tests/mctal/tests/CMakeLists.txt
index 49de87b..28b51a1 100644
--- a/libmcnptools/tests/mctal/tests/CMakeLists.txt
+++ b/libmcnptools/tests/mctal/tests/CMakeLists.txt
@@ -6,6 +6,7 @@ list(APPEND TEST_SRCS
   MctalKcodeCycles.cpp
   MctalKcodeNdat.cpp
   MctalKcodeValue.cpp
+  MctalMergeManyInputs.cpp
   MctalNps.cpp
   MctalRandoms.cpp
   MctalTallyCBins.cpp
diff --git a/libmcnptools/tests/mctal/tests/MctalMergeManyInputs.cpp b/libmcnptools/tests/mctal/tests/MctalMergeManyInputs.cpp
new file mode 100644
index 0000000..893b34a
--- /dev/null
+++ b/libmcnptools/tests/mctal/tests/MctalMergeManyInputs.cpp
@@ -0,0 +1,21 @@
+#include "gtest/gtest.h"
+#include "mcnptools/Mctal.hpp"
+#include "mcnptools/mergeMctals.hpp"
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+TEST(MctalMerge, ManyInputFiles) {
+  const std::string output = "test_mctal_merged_many";
+  std::vector<std::string> mctals(130, "test_mctal");
+  std::remove(output.c_str());
+
+  EXPECT_NO_THROW({
+    mcnptools::Mctal merged = mcnptools::mergeMctals(output, mctals);
+    merged.GetTally(1);
+    merged.GetTally(4);
+  });
+
+  std::remove(output.c_str());
+}