[FFmpeg-devel] [PATCH] avutil/tests/lfg.c: added proper normality test

[Thomas Turner]

On Fri, Feb 24, 2017 at 6:59 PM, Michael Niedermayer <michael at niedermayer.cc
> wrote:

> On Fri, Feb 24, 2017 at 06:43:20PM -0800, Thomas Turner wrote:
> > On Wed, Feb 22, 2017 at 2:16 PM, Michael Niedermayer
> <michael at niedermayer.cc
> > > wrote:
> >
> > > oops forgot to reply to all, this one went only to thomas by mistake
> > >
> > > On Tue, Feb 21, 2017 at 08:12:57PM -0800, Thomas Turner wrote:
> > > >
> > > >
> > > > On 02/17/2017 02:15 PM, Michael Niedermayer wrote:
> > > > > On Thu, Feb 16, 2017 at 08:29:38PM -0800, Thomas Turner wrote:
> > > > >> The Chen-Shapiro(CS) test was used to test normality for
> > > > >> Lagged Fibonacci PRNG.
> > > > >>
> > > > >> Normality Hypothesis Test:
> > > > >>
> > > > >> The null hypothesis formally tests if the population
> > > > >> the sample represents is normally-distributed. For
> > > > >> CS, when the normality hypothesis is True, the
> > > > >> distribution of QH will have a mean close to 1.
> > > > >>
> > > > >> Information on CS can be found here:
> > > > >>
> > > > >> http://www.stata-journal.com/sjpdf.html?articlenum=st0264
> > > > >> http://www.originlab.com/doc/Origin-Help/NormalityTest-Algorithm
> > > > >>
> > > > >> Signed-off-by: Thomas Turner <thomastdt at googlemail.com>
> > > > >> ---
> > > > >>  libavutil/tests/lfg.c    |  170 ++++++--
> > > > >>  tests/fate/libavutil.mak |    4 +
> > > > >>  tests/ref/fate/lfg       | 1007 ++++++++++++++++++++++++++++++
> > > ++++++++++++++++
> > > > >>  3 files changed, 1157 insertions(+), 24 deletions(-)
> > > > >>  create mode 100644 tests/ref/fate/lfg
> > > > >
> > > > > works on x86_64 linux but fails on x86_32
> > > >
> > > > What if we force gcc compiler to use IEEE 754 floating-point
> > > semantics...Will adding the following gcc compilation flags to ffmpeg
> > > configuration allow the test to pass? : -msse2 -mfpmath=sse
> > >
> > > there is no gurantee that the hardware this runs on supports sse
> > > nor that the compiler is gcc
> > >
> > > C has a somewhat loose definition of floating point operations,
> > > that allows C compilers to perform more optimizations and run on more
> > > hardware. There isnt much that can be done about this, short of not
> > > using floating point
> > >
> > > But why does it not work with default options?
> > >
> > x86_32 machine produces a negative overflow for double precision value.
> But
> > unable to figure out precisely why. my guesstimation would be because of
> > the difference in floating point arithmetic.
> >
>
> > > or is that unknown ?
> > > did you succeed in reproduring the issue ?
> > >
> > trying to compile 32bit on my 64bit machine with:
> >
> > ./configure --enable-debug=3 --cc='cc -m32'
> > but i get the following error:
> >
> > cc -m32 is unable to create an executable file.
> > If cc -m32 is a cross-compiler, use the --enable-cross-compile option.
> > Only do this if you know what cross compiling means.
> > C compiler test failed.
>
> try this:
>
> ./configure --cc='ccache gcc' --enable-debug=3 --arch=x86_32
> --target-os=linux --extra-cflags=-m32 --extra-ldflags=-m32
> --enable-cross-compile
>
> still received an error:
ccache gcc is unable to create an executable file.
C compiler test failed.

I've attached the log file produced by the ./configure, if that helps


> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Observe your enemies, for they first find out your faults. -- Antisthenes
>
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>
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