Fix Issue #182

Author: thelfer

src/MaterialStateManager.cxx

@@ -303,8 +303,8 @@ namespace mgis::behaviour {
       std::copy(from.begin(), from.end(), to.begin());
     };  // end update_span
     auto update_field_holder =
-        [&check_size](MaterialStateManager::FieldHolder& to,
-                      const MaterialStateManager::FieldHolder& from) {
+        [&o, &check_size](MaterialStateManager::FieldHolder& to,
+                          const MaterialStateManager::FieldHolder& from) {
           if (std::holds_alternative<mgis::real>(from)) {
             to = std::get<mgis::real>(from);
           } else if (std::holds_alternative<std::vector<mgis::real>>(from)) {
@@ -317,6 +317,11 @@ namespace mgis::behaviour {
             } else if (std::holds_alternative<std::vector<mgis::real>>(to)) {
               // reuse existing memory
               auto& to_v = std::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 {
@@ -332,7 +337,12 @@ namespace mgis::behaviour {
               std::copy(from_v.begin(), from_v.end(), to_v.begin());
             } else if (std::holds_alternative<std::vector<mgis::real>>(to)) {
               // reuse existing memory
-              auto to_v = std::get<std::vector<mgis::real>>(to);
+              auto& to_v = std::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 {