Fix Issue #182

Author: thelfer

src/MaterialStateManager.cxx

@@ -392,7 +392,7 @@ namespace mgis {
         std::copy(from.begin(), from.end(), to.begin());
       };  // end update_span
       auto update_field_holder =
-          [&check_size](MaterialStateManager::FieldHolder& to,
+          [&o, &check_size](MaterialStateManager::FieldHolder& to,
                         const MaterialStateManager::FieldHolder& from) {
             if (mgis::holds_alternative<mgis::real>(from)) {
               to = mgis::get<mgis::real>(from);
@@ -406,6 +406,11 @@ namespace mgis {
               } else if (mgis::holds_alternative<std::vector<mgis::real>>(to)) {
                 // reuse existing memory
                 auto& to_v = mgis::get<std::vector<mgis::real>>(to);
+                if (to_v.size() != from_v.size()) {
+                  if (to_v.size() * o.n == from_v.size()) {
+                    to_v.resize(from_v.size());
+                  }
+                }
                 check_size(from_v.size(), to_v.size());
                 std::copy(from_v.begin(), from_v.end(), to_v.begin());
               } else {
@@ -421,7 +426,12 @@ namespace mgis {
                 std::copy(from_v.begin(), from_v.end(), to_v.begin());
               } else if (mgis::holds_alternative<std::vector<mgis::real>>(to)) {
                 // reuse existing memory
-                auto to_v = mgis::get<std::vector<mgis::real>>(to);
+                auto& to_v = mgis::get<std::vector<mgis::real>>(to);
+                if (to_v.size() != from_v.size()) {
+                  if (to_v.size() * o.n == from_v.size()) {
+                    to_v.resize(from_v.size());
+                  }
+                }
                 check_size(from_v.size(), to_v.size());
                 std::copy(from_v.begin(), from_v.end(), to_v.begin());
               } else {