60 lines
2.9 KiB
Markdown
60 lines
2.9 KiB
Markdown
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# Benchmark Tools
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## compare_bench.py
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The `compare_bench.py` utility which can be used to compare the result of benchmarks.
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The program is invoked like:
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``` bash
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$ compare_bench.py <old-benchmark> <new-benchmark> [benchmark options]...
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```
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Where `<old-benchmark>` and `<new-benchmark>` either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
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The sample output using the JSON test files under `Inputs/` gives:
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``` bash
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$ ./compare_bench.py ./gbench/Inputs/test1_run1.json ./gbench/Inputs/test1_run2.json
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Comparing ./gbench/Inputs/test1_run1.json to ./gbench/Inputs/test1_run2.json
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Benchmark Time CPU
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----------------------------------------------
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BM_SameTimes +0.00 +0.00
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BM_2xFaster -0.50 -0.50
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BM_2xSlower +1.00 +1.00
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BM_10PercentFaster -0.10 -0.10
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BM_10PercentSlower +0.10 +0.10
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```
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When a benchmark executable is run, the raw output from the benchmark is printed in real time to stdout. The sample output using `benchmark/basic_test` for both arguments looks like:
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```
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./compare_bench.py test/basic_test test/basic_test --benchmark_filter=BM_empty.*
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RUNNING: test/basic_test --benchmark_filter=BM_empty.*
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Run on (4 X 4228.32 MHz CPU s)
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2016-08-02 19:21:33
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Benchmark Time CPU Iterations
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--------------------------------------------------------------------
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BM_empty 9 ns 9 ns 79545455
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BM_empty/threads:4 4 ns 9 ns 75268816
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BM_empty_stop_start 8 ns 8 ns 83333333
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BM_empty_stop_start/threads:4 3 ns 8 ns 83333332
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RUNNING: test/basic_test --benchmark_filter=BM_empty.*
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Run on (4 X 4228.32 MHz CPU s)
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2016-08-02 19:21:35
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Benchmark Time CPU Iterations
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--------------------------------------------------------------------
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BM_empty 9 ns 9 ns 76086957
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BM_empty/threads:4 4 ns 9 ns 76086956
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BM_empty_stop_start 8 ns 8 ns 87500000
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BM_empty_stop_start/threads:4 3 ns 8 ns 88607596
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Comparing test/basic_test to test/basic_test
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Benchmark Time CPU
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---------------------------------------------------------
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BM_empty +0.00 +0.00
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BM_empty/threads:4 +0.00 +0.00
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BM_empty_stop_start +0.00 +0.00
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BM_empty_stop_start/threads:4 +0.00 +0.00
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```
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Obviously this example doesn't give any useful output, but it's intended to show the output format when 'compare_bench.py' needs to run benchmarks.
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