MSVC++ before 2015 Update 2 has a bug in sleep_for where it tries to
implicitly += the input with a nanoseconds variable. Work around this by
using nanoseconds directly (which can be implicitly +='d with
chrono::nanoseconds).
Having access to the thread count from within a benchmark is useful,
for when one wants to distribute a workload dynamically among the
benchmarks running in parallel e.g when using ThreadRange() or
ThreadPerCpu().
This patch adopts a new internal structure for how timings are performed.
Currently every iteration of a benchmark checks to see if it has been running
for an appropriate amount of time. Checking the clock introduces noise into
the timings and this can cause inconsistent output from each benchmark.
Now every iteration of a benchmark only checks an iteration count to see if it
should stop running. The iteration count is determined before hand by testing
the benchmark on a series of increasing iteration counts until a suitable count
is found. This increases the amount of time it takes to run the actual benchmarks
but it also greatly increases the accuracy of the results.
This patch introduces some breaking changes. The notable breaking changes are:
1. Benchmarks run on multiple threads no generate a report per thread. Instead
only a single report is generated.
2. ::benchmark::UseRealTime() was removed and replaced with State::UseRealTime().
Fixes#89
UseRealTime was defined in the internal namespace by mistake.
Similarly, documentation suggested that benchmark::SetLabel should be
used to set a label, and a function was declared but not defined, while
actually the call should be 'state.SetLabel'.
This patch does two things:
1. It overhalls the static initialization in Walltime to be simplier. It uses
a static variable inside WallTime::Now() to initialize the timer.
2. Add a logging mechanism so that the -v flag actually has meaning and
reimplement the CHECK macros to allow extra messages to be streamed in.
This patch cleans up our use of generic macros and also merges changes in the
build system.
It adds options -DBENCHMARK_ENABLE_TESTING and -DBENCHMARK_ENABLE_SHARED.
Previously the benchmark_test program executed the benchmark tests to make sure
the API was working but was not checking the number of tests that were
completed. If the regular expression matching breaks, zero tests could be ran.
Similarly, if one of the APIs breaks and doesn't run the correct amount of tests
then `make test` will catch this.
Benchmark library builds and runs but only single-threaded. Multithreaded
support needs a bit more love.
Currently requires some C++11 support (g++ 4.6.3 seems to work).
