| -rw-r--r-- | doc/gsl-shell-index/benchmarks.rst | 55 |
diff --git a/doc/gsl-shell-index/benchmarks.rst b/doc/gsl-shell-index/benchmarks.rst new file mode 100644 index 00000000..76374332 --- /dev/null +++ b/doc/gsl-shell-index/benchmarks.rst @@ -0,0 +1,55 @@ + +.. _benchmarks: + +Benchmarks +========== + +The performance of the algorithms implemented in GSL Shell have been tested agaist an equivalent C implementation. + +The purpose of the benchmarks is twofold. One of the objectives is to test the correctness of the results against the native GSL implementation while the other is to compare C and Lua implementation in term of performance. + +The performance is measured simply in term of time of execution, no attemt has been done to add other factors like memory utilisation or others. + +Besides the benchmark of optimized C code the LuaJIT2 implementation was tested with and without the JIT support enabled. +When the JIT support is disabled (option ``-joff``) the algorithm is executed in purely interpreted mode. +This latter result is reported to give an idea of the improvement given by the JIT compiler. + +Results +------- + +We present here the results of the benchmark in term of execution time. +The time is normalized taking the ratio with the 'LuaJIT2' results. +The ratio obtained is therefore plotted in logarithmic scale. + +.. figure:: gsl-shell-benchmark.png + +A few remarks about these results. + +Only a very few ODE algorithms are currently implemented in GSL Shell and these use an interface different of those used in the GSL library. +In GSL Shell the variables of the ode system are not packed into an array but are passed like function arguments. +One implication is that only ODE system with a small number of variables can be integrated. +This difference can affect the execution speed and should be kept in mind. + +Otherwise there is nothing that prevents the implementation in GSL Shell of an ODE integrator in array form. +This is actually planned to be done in the near future. + +For all the other algorithms the GSL implementation closely mirror the GSL interface and the comparaison is aboslutely fair. + + +Technical details +----------------- + +The C and Lua version of the benchmark was written to solve exactly the same problem with the same input values and the same algorithm parameters. + +The C version of the benchmark was compiled using the following compiler flags: ``-O2 -fomit-frame-pointer``. +The GSL library itself was compiled with the same options and the executable was created by linking to the GSL shared library. + +While some tweak of the compiler options are possible to improve performance of GSL C code no attempt was done in this direction. +The idea was that we want to compare the Lua implementation with a C executable compiled with standard optimizing options and in accord to common practices. + +Benchmark availability +---------------------- + +The source code of all the benchmark is available with the GSL Shell source code inside the 'benchmarks' folder. + +We encourage all the interested users to reproduce the benchmarks results by themselves. |