>From a443d9907737390cda05c1c14da7c6c1044f25db Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <address@hidden>
Date: Fri, 27 Feb 2015 18:56:08 +0100
Subject: [PATCH] Allow computing MemberSymbolTable member access index and
 reusing it.

Looking up the member by name once and then reusing the index to access it
results in a big performance gain when doing it many times in a row, e.g.
CensusView::column_value_varies_across_cells() now takes less than 30% of the
time it took before for a census with ~4000 rows.
---
 any_member.hpp  | 28 ++++++++++++++++++++++------
 census_view.cpp |  7 +++++--
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/any_member.hpp b/any_member.hpp
index 8e5f4a6..ca34394 100644
--- a/any_member.hpp
+++ b/any_member.hpp
@@ -548,6 +548,9 @@ class MemberSymbolTable
     bool equals(MemberSymbolTable<ClassType> const&) const;
     std::vector<std::string> const& member_names() const;
 
+    size_t get_member_index(std::string const&) const;
+    any_member<ClassType> const& get_member_by_index(size_t) const;
+
   protected:
     MemberSymbolTable();
 
@@ -616,17 +619,30 @@ void MemberSymbolTable<ClassType>::complain_that_no_such_member_is_ascribed
 }
 
 template<typename ClassType>
-any_member<ClassType>& MemberSymbolTable<ClassType>::operator[]
-    (std::string const& s
-    )
+size_t MemberSymbolTable<ClassType>::get_member_index(std::string const& s) const
 {
-    typedef std::vector<std::string>::iterator svi;
-    svi i = std::lower_bound(member_names_.begin(), member_names_.end(), s);
+    typedef std::vector<std::string>::const_iterator svci;
+    svci i = std::lower_bound(member_names_.begin(), member_names_.end(), s);
     if(member_names_.end() == i || s != *i)
         {
         complain_that_no_such_member_is_ascribed(s);
         }
-    return member_values_[i - member_names_.begin()];
+    return i - member_names_.begin();
+}
+
+template<typename ClassType>
+any_member<ClassType> const&
+MemberSymbolTable<ClassType>::get_member_by_index(size_t n) const
+{
+    return member_values_[n];
+}
+
+template<typename ClassType>
+any_member<ClassType>& MemberSymbolTable<ClassType>::operator[]
+    (std::string const& s
+    )
+{
+    return member_values_[get_member_index(s)];
 }
 
 template<typename ClassType>
diff --git a/census_view.cpp b/census_view.cpp
index cfc3f66..eb7be4b 100644
--- a/census_view.cpp
+++ b/census_view.cpp
@@ -936,9 +936,12 @@ Input* CensusView::class_parms_from_class_name(std::string const& class_name)
     const any_member<Input>& case_value = case_parms()[0][header];
 
     typedef std::vector<Input>::const_iterator ici;
-    for(ici j = cells.begin(); j != cells.end(); ++j)
+    ici j = cells.begin();
+    size_t const header_index = j->get_member_index(header);
+
+    for(; j != cells.end(); ++j)
         {
-        if(!((*j)[header] == case_value))
+        if(!(j->get_member_by_index(header_index) == case_value))
             {
             return true;
             }
-- 
2.1.0