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benchmarks: fix output formatting

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snprintf is a better tool for this task, anyway, but here's what was
wrong with the stream formatting:

s << name << ":" << std::setw(45 - (int)s.tellp())

cannot be used to align columns, tellp() may return any of:
    0
    name.length()
    name.length() + strlen(":")

because the compiler is allowed to reorder the evaluation of
sub-expressions as it likes -- it may evaluate s.tellp() before
evaluating (s << name) or in-between (s << name) and (s << ":")

try with gcc-4.8
This commit is contained in:
Mickey Rose 2016-02-16 16:27:32 +01:00
parent 5d1fd56cef
commit 90fcdc90d3
1 changed files with 11 additions and 9 deletions
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20
benchmark/bench_framework.hpp
View file

@ -9,7 +9,7 @@
// stl
#include <chrono>
#include <iomanip>
#include <cstdio> // snprintf
#include <iostream>
#include <set>
#include <sstream>
@ -96,11 +96,7 @@ int run(T const& test_runner, std::string const& name)
{
std::chrono::high_resolution_clock::time_point start;
std::chrono::high_resolution_clock::duration elapsed;
std::stringstream s;
s << name << ":"
<< std::setw(45 - (int)s.tellp()) << std::right
<< " t:" << test_runner.threads()
<< " i:" << test_runner.iterations();
if (test_runner.threads() > 0)
{
using thread_group = std::vector<std::unique_ptr<std::thread> >;
@ -120,9 +116,15 @@ int run(T const& test_runner, std::string const& name)
test_runner();
elapsed = std::chrono::high_resolution_clock::now() - start;
}
s << std::setw(65 - (int)s.tellp()) << std::right
<< std::chrono::duration_cast<std::chrono::milliseconds>(elapsed).count() << " milliseconds\n";
std::clog << s.str();
char msg[200];
std::snprintf(msg, sizeof(msg),
"%-43s %3zu threads %9zu iters %6.0f milliseconds",
name.c_str(),
test_runner.threads(),
test_runner.iterations(),
std::chrono::duration<double, std::milli>(elapsed).count());
std::clog << msg << "\n";
}
return 0;
}