[lmi-commits] [lmi] master cbb6cad 4/4: Measure speed of various stream-cast implementations

[Greg Chicares]

branch: master
commit cbb6cade2f89a3bada06860f5179c4695662b137
Author: Gregory W. Chicares <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Measure speed of various stream-cast implementations
    
    The purpose of the added tests is to measure various speed improvements,
    and ultimately to make stream_cast<>() and ledger_format() faster. See:
      https://lists.nongnu.org/archive/html/lmi/2019-01/msg00005.html
    et seqq.
---
 Makefile.am          |   3 +-
 objects.make         |   1 +
 stream_cast_test.cpp | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/Makefile.am b/Makefile.am
index c4909cc..4ee10cb 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1075,7 +1075,8 @@ test_stratified_algorithms_CXXFLAGS = $(AM_CXXFLAGS)
 test_stream_cast_SOURCES = \
   $(common_test_objects) \
   facets.cpp \
-  stream_cast_test.cpp
+  stream_cast_test.cpp \
+  timer.cpp
 test_stream_cast_CXXFLAGS = $(AM_CXXFLAGS)
 
 test_system_command_SOURCES = \
diff --git a/objects.make b/objects.make
index a45395b..c1c89d5 100644
--- a/objects.make
+++ b/objects.make
@@ -949,6 +949,7 @@ stream_cast_test$(EXEEXT): \
   $(common_test_objects) \
   facets.o \
   stream_cast_test.o \
+  timer.o \
 
 system_command_test$(EXEEXT): \
   $(common_test_objects) \
diff --git a/stream_cast_test.cpp b/stream_cast_test.cpp
index 720f3e5..d391ed6 100644
--- a/stream_cast_test.cpp
+++ b/stream_cast_test.cpp
@@ -24,6 +24,114 @@
 #include "stream_cast.hpp"
 
 #include "test_tools.hpp"
+#include "timer.hpp"
+
+/// A minimalistic clone of stream_cast<>().
+
+template<typename To, typename From>
+To cast_1(From from, To = To())
+{
+    std::stringstream interpreter;
+    interpreter.imbue(blank_is_not_whitespace_locale());
+
+    To result = To();
+    if
+        (  !(interpreter << from)
+        || !(interpreter >> result)
+        || !(interpreter >> std::ws).eof()
+        )
+        {
+        throw std::runtime_error("Oops!");
+        }
+    return result;
+}
+
+/// Like cast_1<>(), but with static 'interpreter'.
+
+template<typename To, typename From>
+To cast_2(From from, To = To())
+{
+    static std::stringstream interpreter;
+    interpreter.imbue(blank_is_not_whitespace_locale());
+    interpreter.str(std::string{});
+    interpreter.clear();
+
+    To result = To();
+    if
+        (  !(interpreter << from)
+        || !(interpreter >> result)
+        || !(interpreter >> std::ws).eof()
+        )
+        {
+        throw std::runtime_error("Oops!");
+        }
+    return result;
+}
+
+std::stringstream& imbued()
+{
+    static std::stringstream interpreter;
+    interpreter.imbue(blank_is_not_whitespace_locale());
+    return interpreter;
+}
+
+/// Like cast_2<>(), but with statically imbued static 'interpreter'.
+
+template<typename To, typename From>
+To cast_3(From from, To = To())
+{
+    std::stringstream& interpreter {imbued()};
+    interpreter.str(std::string{});
+    interpreter.clear();
+    To result = To();
+    if
+        (  !(interpreter << from)
+        || !(interpreter >> result)
+        || !(interpreter >> std::ws).eof()
+        )
+        {
+        throw std::runtime_error("Oops!");
+        }
+    return result;
+}
+
+/// Like cast_3<>(), but without calling str().
+
+template<typename To, typename From>
+To cast_4(From from, To = To())
+{
+    std::stringstream& interpreter {imbued()};
+    interpreter.clear();
+    To result = To();
+    if
+        (  !(interpreter << from)
+        || !(interpreter >> result)
+        || !(interpreter >> std::ws).eof()
+        )
+        {
+        throw std::runtime_error("Oops!");
+        }
+    return result;
+}
+
+void assay_speed()
+{
+    static double const e {2.718281828459045};
+    auto f0 = [] {stream_cast<std::string>(e);};
+    auto f1 = [] {cast_1     <std::string>(e);};
+    auto f2 = [] {cast_2     <std::string>(e);};
+    auto f3 = [] {cast_3     <std::string>(e);};
+    auto f4 = [] {cast_4     <std::string>(e);};
+    std::cout
+        << "\n  Speed tests..."
+        << "\n  stream_cast     : " << TimeAnAliquot(f0)
+        << "\n  minimalistic    : " << TimeAnAliquot(f1)
+        << "\n  static stream   : " << TimeAnAliquot(f2)
+        << "\n  static facet too: " << TimeAnAliquot(f3)
+        << "\n  without str()   : " << TimeAnAliquot(f4)
+        << std::endl
+        ;
+}
 
 int test_main(int, char*[])
 {
@@ -98,6 +206,8 @@ int test_main(int, char*[])
         ,"Cannot convert (char const*)(0) to std::string."
         );
 
+    assay_speed();
+
     return 0;
 }