Eliminate unnecessary copy operations in function parameters and range-based loops (#8589)

src/test/lp/argument_parser.h

@@ -42,19 +42,19 @@ public:
         }
     }
 
-    void add_option(std::string s) {
+    void add_option(const std::string& s) {
         add_option_with_help_string(s, "");
     }
 
-    void add_option_with_help_string(std::string s, std::string help_string) {
+    void add_option_with_help_string(const std::string& s, const std::string& help_string) {
         m_options[s]=help_string;
     }
 
-    void add_option_with_after_string(std::string s) {
+    void add_option_with_after_string(const std::string& s) {
         add_option_with_after_string_with_help(s, "");
     }
 
-    void add_option_with_after_string_with_help(std::string s, std::string help_string) {
+    void add_option_with_after_string_with_help(const std::string& s, const std::string& help_string) {
         m_options_with_after_string[s]=help_string;
     }
 
@@ -82,19 +82,19 @@ public:
         return status_is_ok;
     }
 
-    bool contains(std::unordered_map<std::string, std::string> & m, std::string s) {
+    bool contains(std::unordered_map<std::string, std::string> & m, const std::string& s) {
         return m.find(s) != m.end();
     }
 
-    bool contains(std::set<std::string> & m, std::string s) {
+    bool contains(std::set<std::string> & m, const std::string& s) {
         return m.find(s) != m.end();
     }
 
-    bool option_is_used(std::string option) {
+    bool option_is_used(const std::string& option) {
         return contains(m_used_options, option) || contains(m_used_options_with_after_string, option);
     }
 
-    std::string get_option_value(std::string option) {
+    std::string get_option_value(const std::string& option) {
         auto t = m_used_options_with_after_string.find(option);
         if (t != m_used_options_with_after_string.end()){
             return t->second;
@@ -102,11 +102,11 @@ public:
         return std::string();
     }
 
-    bool starts_with(std::string s, char const * prefix) {
+    bool starts_with(const std::string& s, char const * prefix) {
         return starts_with(s, std::string(prefix));
     }
 
-    bool starts_with(std::string s, std::string prefix) {
+    bool starts_with(const std::string& s, const std::string& prefix) {
         return s.substr(0, prefix.size()) == prefix;
     }
 

src/test/lp/lp.cpp

@@ -684,11 +684,11 @@ std::string create_output_file_name(bool minimize, std::string file_name,
 }
 
 std::string create_output_file_name_for_glpsol(bool minimize,
-                                               std::string file_name) {
+                                               const std::string& file_name) {
     return file_name + (minimize ? "_min" : "_max") + "_glpk_out";
 }
 
-int run_glpk(std::string file_name, std::string glpk_out_file_name,
+int run_glpk(const std::string& file_name, const std::string& glpk_out_file_name,
              bool minimize, unsigned time_limit) {
     std::string minmax(minimize ? "--min" : "--max");
     std::string tmlim = time_limit > 0 ? std::string(" --tmlim ") +
@@ -700,7 +700,7 @@ int run_glpk(std::string file_name, std::string glpk_out_file_name,
     return system(command_line.c_str());
 }
 
-std::string get_status(std::string file_name) {
+std::string get_status(const std::string& file_name) {
     std::ifstream f(file_name);
     if (!f.is_open()) {
         std::cout << "cannot open " << file_name << std::endl;
@@ -728,7 +728,7 @@ struct sort_pred {
     }
 };
 
-vector<std::string> get_file_names_from_file_list(std::string filelist) {
+vector<std::string> get_file_names_from_file_list(const std::string& filelist) {
     std::ifstream file(filelist);
     if (!file.is_open()) {
         std::cout << "cannot open " << filelist << std::endl;

src/test/lp/smt_reader.h

@@ -66,7 +66,7 @@ namespace lp {
             lconstraint_kind m_kind;
             std::vector<std::pair<mpq, std::string>> m_coeffs;
             mpq m_right_side;
-            void add_pair(mpq c, std::string name) {
+            void add_pair(mpq c, const std::string& name) {
                 m_coeffs.push_back(make_pair(c, name));
             }
             formula_constraint() : m_right_side(numeric_traits<mpq>::zero()) {}
@@ -81,7 +81,7 @@ namespace lp {
         std::string                               m_file_name;
         std::ifstream                             m_file_stream;
         std::string                               m_line;
-        smt_reader(std::string file_name):
+        smt_reader(const std::string& file_name):
             m_is_OK(true),
             m_line_number(0),
             m_file_name(file_name), 
@@ -372,7 +372,7 @@ namespace lp {
         }
         */
 
-        unsigned register_name(std::string s) {
+        unsigned register_name(const std::string& s) {
             auto it = m_name_to_var_index.find(s);
             if (it!= m_name_to_var_index.end())
                 return it->second;

src/test/lp/test_file_reader.h

@@ -59,7 +59,7 @@ class test_file_reader {
     std::ifstream m_file_stream;
 public:
     // constructor
-    test_file_reader(std::string file_name) :  m_file_stream(file_name) {
+    test_file_reader(const std::string& file_name) :  m_file_stream(file_name) {
         if (!m_file_stream.is_open()) {
             std::cout << "cannot open file " << "\'" << file_name << "\'" << std::endl;
         }