[lmi-commits] [lmi] master de40a50 4/4: Simplify simplify_floating_point()

[Greg Chicares]

branch: master
commit de40a50a80642f735888bd957d6ed2fa4b9c059d
Author: Gregory W. Chicares <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Simplify simplify_floating_point()
    
    The decision tree here:
      http://lists.nongnu.org/archive/html/lmi/2018-02/msg00157.html
    selects this more scrutable algorithm based on performance measurements
    using the unit test:
    
    new algorithm, then old: median of five runs
      2/3, lmi  : 4.042e-006 s mean;          4 us least of 2474 runs
      2/3, lmi  : 3.983e-006 s mean;          4 us least of 2511 runs
    
    new algorithm, then old: fastest of five runs
      2/3, lmi  : 3.758e-006 s mean;          4 us least of 2661 runs
      2/3, lmi  : 3.539e-006 s mean;          3 us least of 2826 runs
    
    That comparison measures mete_two_thirds(), which converts from double
    to string and back again: it doesn't measure simplify_floating_point()
    in isolation, but it demonstrates that there's no gross pessimization
    that would override the desire for clarity.
---
 Makefile.am           | 10 +++++++++-
 numeric_io_traits.hpp | 14 +++++---------
 objects.make          |  8 ++++++++
 3 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index 07f475d..2d2f3d5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -569,7 +569,8 @@ test_alert_CXXFLAGS = $(AM_CXXFLAGS)
 test_any_member_SOURCES = \
   $(common_test_objects) \
   any_member_test.cpp \
-  facets.cpp
+  facets.cpp \
+  miscellany.cpp
 test_any_member_CXXFLAGS = $(AM_CXXFLAGS)
 
 test_assert_lmi_SOURCES = \
@@ -723,6 +724,7 @@ test_gpt_SOURCES = \
   gpt_commutation_functions.cpp \
   gpt_test.cpp \
   ihs_irc7702.cpp \
+  miscellany.cpp \
   timer.cpp
 test_gpt_CXXFLAGS = $(AM_CXXFLAGS)
 
@@ -868,6 +870,7 @@ test_mortality_rates_CXXFLAGS = $(AM_CXXFLAGS)
 test_name_value_pairs_SOURCES = \
   $(common_test_objects) \
   facets.cpp \
+  miscellany.cpp \
   name_value_pairs.cpp \
   name_value_pairs_test.cpp
 test_name_value_pairs_CXXFLAGS = $(AM_CXXFLAGS)
@@ -881,6 +884,7 @@ test_ncnnnpnn_CXXFLAGS = $(AM_CXXFLAGS)
 
 test_numeric_io_SOURCES = \
   $(common_test_objects) \
+  miscellany.cpp \
   numeric_io_test.cpp \
   timer.cpp
 test_numeric_io_CXXFLAGS = $(AM_CXXFLAGS)
@@ -929,6 +933,7 @@ test_premium_tax_LDADD = \
 test_print_matrix_SOURCES = \
   $(common_test_objects) \
   facets.cpp \
+  miscellany.cpp \
   print_matrix_test.cpp
 test_print_matrix_CXXFLAGS = $(AM_CXXFLAGS)
 
@@ -1054,6 +1059,7 @@ test_tn_range_SOURCES = \
   $(common_test_objects) \
   datum_base.cpp \
   facets.cpp \
+  miscellany.cpp \
   tn_range_test.cpp \
   tn_range_test_aux.cpp
 test_tn_range_CXXFLAGS = $(AM_CXXFLAGS)
@@ -1061,6 +1067,7 @@ test_tn_range_CXXFLAGS = $(AM_CXXFLAGS)
 test_value_cast_SOURCES = \
   $(common_test_objects) \
   facets.cpp \
+  miscellany.cpp \
   value_cast_test.cpp
 test_value_cast_CXXFLAGS = $(AM_CXXFLAGS)
 
@@ -1078,6 +1085,7 @@ test_wx_new_CXXFLAGS = $(AM_CXXFLAGS)
 test_xml_serialize_SOURCES = \
   $(common_test_objects) \
   facets.cpp \
+  miscellany.cpp \
   timer.cpp \
   xml_lmi.cpp \
   xml_serialize_test.cpp
diff --git a/numeric_io_traits.hpp b/numeric_io_traits.hpp
index 93ea6a3..ebfd102 100644
--- a/numeric_io_traits.hpp
+++ b/numeric_io_traits.hpp
@@ -26,6 +26,7 @@
 
 #include "bourn_cast.hpp"
 #include "ieee754.hpp"                  // is_infinite<>()
+#include "miscellany.hpp"               // rtrim()
 
 #include <algorithm>                    // max()
 #include <cmath>                        // fabs(), log10()
@@ -92,15 +93,10 @@ inline int floating_point_decimals(T t)
 
 inline std::string simplify_floating_point(std::string const& s)
 {
-    std::string::const_reverse_iterator ri = s.rbegin();
-  loop:
-    switch(*ri)
-        {
-        case '0': ++ri; goto loop;
-        case '.': ++ri;
-        default : ;
-        }
-    return std::string(s.begin(), ri.base());
+    std::string z(s);
+    rtrim(z, "0");
+    rtrim(z, ".");
+    return z;
 }
 
 /// Traits for conversion between arithmetic types and strings.
diff --git a/objects.make b/objects.make
index 6960d89..04e4f9b 100644
--- a/objects.make
+++ b/objects.make
@@ -512,6 +512,7 @@ any_member_test$(EXEEXT): \
   $(common_test_objects) \
   any_member_test.o \
   facets.o \
+  miscellany.o \
 
 assert_lmi_test$(EXEEXT): \
   $(common_test_objects) \
@@ -642,6 +643,7 @@ gpt_test$(EXEEXT): \
   gpt_commutation_functions.o \
   gpt_test.o \
   ihs_irc7702.o \
+  miscellany.o \
   timer.o \
 
 handle_exceptions_test$(EXEEXT): \
@@ -772,6 +774,7 @@ name_value_pairs_test$(EXEEXT): \
   $(boost_filesystem_objects) \
   $(common_test_objects) \
   facets.o \
+  miscellany.o \
   name_value_pairs.o \
   name_value_pairs_test.o \
 
@@ -781,6 +784,7 @@ ncnnnpnn_test$(EXEEXT): \
 
 numeric_io_test$(EXEEXT): \
   $(common_test_objects) \
+  miscellany.o \
   numeric_io_test.o \
   timer.o \
 
@@ -824,6 +828,7 @@ premium_tax_test$(EXEEXT): \
 print_matrix_test$(EXEEXT): \
   $(common_test_objects) \
   facets.o \
+  miscellany.o \
   print_matrix_test.o \
 
 product_file_test$(EXEEXT): \
@@ -935,12 +940,14 @@ tn_range_test$(EXEEXT): \
   $(common_test_objects) \
   datum_base.o \
   facets.o \
+  miscellany.o \
   tn_range_test.o \
   tn_range_test_aux.o \
 
 value_cast_test$(EXEEXT): \
   $(common_test_objects) \
   facets.o \
+  miscellany.o \
   value_cast_test.o \
 
 vector_test$(EXEEXT): \
@@ -956,6 +963,7 @@ xml_serialize_test$(EXEEXT): \
   $(common_test_objects) \
   $(xmlwrapp_objects) \
   facets.o \
+  miscellany.o \
   timer.o \
   xml_lmi.o \
   xml_serialize_test.o \