2020-08-20 19:19:49 +08:00
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# Sandboxing PFFFT library
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Builder: CMake
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OS: Linux
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### For testing:
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`cd build`, then `./pffft_sandboxed`
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### For debug:
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`SAPI_VLOG_LEVEL=1 ./pffft_sandboxed --v=100
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--sandbox2_danger_danger_permit_all_and_log <auxiliar file>`
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## ***About the project***
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*PFFFT library is concerned with 1D Fast-Fourier Transformations finding a
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compromise between accuracy and speed. It deals with real and complex
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vectors, both cases being illustrated in the testing part (`main_pffft.c`
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for initially and original version, `main_pffft_sandboxed.cc` for our
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currently implemented sandboxed version).
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The original files can be found at: https://bitbucket.org/jpommier/pffft/src.*
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*The purpose of sandboxing is to limit the permissions and capabilities of
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library’s methods, in order to secure the usage of them.
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After obtaining the sandbox, the functions will be called through an
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Sandbox API (being called `api` in the current test) and so, the
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operations, system calls or namspaces access may be controlled.
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From both `pffft.h` and `fftpack.h` headers, useful methods are added to
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sapi library builded with CMake. There is also a need to link math library
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as the transformations made require mathematical operators.
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Regarding the testing of the methods, one main is doing this job by
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iterating through a set of values, that represents the accuracy of
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transformations and print the speed for each value and type of
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transformation. More specifically, the input length is the target for
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accuracy (named as `N`) and it stands for the number of data points from
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the series that calculate the result of transformation. It is also
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important to mention that the `cplx` variable stands for a boolean value
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that tells the type of transformation (0 for REAL and 1 for COMPLEX) and
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it is taken into account while testing.
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In the end, the performance of PFFFT library it is outlined by the output.*
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#### CMake observations resume:
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* linking pffft and fftpack (which contains necessary functions for pffft)
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* set math library
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#### Sandboxed main observations resume:
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* containing two testing parts (fft / pffft benchmarks)
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* showing the performance of the transformations implies
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testing them through various FFT dimenstions.
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Variable N, the input length, will take specific values
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meaning the number of points to which it is set the calculus
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(more details of mathematical purpose of N - https://en.wikipedia.org/wiki/Cooley%E2%80%93Tukey_FFT_algorithm).
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* output shows speed depending on the input length
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### Bugs history
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- [Solved] pffft benchmark bug: "Sandbox not active"
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N = 64, status OK, pffft_transform generates error
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N > 64, status not OK
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Problem on initialising sapi::StatusOr<PFFFT_Setup *> s; the memory that stays
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for s is not the same with the address passed in pffft_transform function.
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(sapi :: v :: GenericPtr - to be changed)
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Temporary solution: change the generated files to accept
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uintptr_t instead of PFFFT_Setup
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Solution: using "sapi::v::RemotePtr" instead of "sapi::v::GenericPtr"
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2020-08-20 20:37:34 +08:00
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to access the memory of object s
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- [Unresolved] compiling bug: "No spave left on device"
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The building process creates some `embed` files that use lots of
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memory, trying to write them on /tmp.
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Temporary solution: clean /tmp directory by `sudo rm -rf /tmp/*`.
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