Source code is from Boost:
http://www.boost.org/doc/libs/1_46_1/boost/math/special_functions/erf.hpp
with appropriate modifications for FFmpeg.
Tested on interval -6 to 6 (beyond which it saturates), +/-NAN, +/-INFINITY
under -fsanitize=undefined on clang to test for possible undefined behavior.
This function turns out to actually be essentially as accurate and faster than the
libm (GNU/BSD's/Mac OS X), and I can think of 3 reasons why upstream
does not use this:
1. They are not aware of it.
2. They are concerned about licensing - this applies especially to GNU
libm.
3. They do not know and/or appreciate the benefits of rational
approximations over polynomial approximations. Boost uses them to great
effect, see e.g swr/resample for bessel derived from them, which is also
similarly superior to libm variants.
First, performance.
sample benchmark (clang -O3, Haswell, GNU/Linux):
3e8 values evenly spaced from 0 to 6
time (libm):
./test 13.39s user 0.00s system 100% cpu 13.376 total
time (boost based):
./test 9.20s user 0.00s system 100% cpu 9.190 total
Second, accuracy.
1e8 eval pts from 0 to 6
maxdiff (absolute): 2.2204460492503131e-16
occuring at point where libm erf is correctly rounded, this is not.
Illustration of superior rounding of this function:
arg : 0.83999999999999997
erf : 0.76514271145499457
boost : 0.76514271145499446
real : 0.76514271145499446
i.e libm is actually incorrectly rounded. Note that this is clear from:
https://github.com/JuliaLang/openlibm/blob/master/src/s_erf.c (the Sun
implementation used by both BSD and GNU libm's), where only 1 ulp is
guaranteed.
Reasons it is not easy/worthwhile to create a "correctly rounded"
variant of this function (i.e 0.5ulp):
1. Upstream libm's don't do it anyway, so we can't guarantee this unless
we force this implementation on all platforms. This is not easy, as the
linker would complain unless measures are taken.
2. Nothing in FFmpeg cares or can care about such things, due to the
above and FFmpeg's nature.
3. Creating a correctly rounded function will in practice need some use of long
double/fma. long double, although C89/C90, unfortunately has problems on
ppc. This needs fixing of toolchain flags/configure. In any case this
will be slower for miniscule gain.
Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
For systems with broken libms.
Tested with NAN, -NAN, INFINITY, -INFINITY, +/-x for regular double x and
combinations of these.
Old versions of MSVC need some UINT64_C hackery.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Reviewed-by: Hendrik Leppkes <h.leppkes@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
Commit 14ea4151d7 had a bug in that the
conversion of the uint64_t result to an int (the return signature) would
lead to implementation defined behavior, and in this case simply
returned 0 for NAN. A fix via AND'ing the result with 1 does the trick,
simply by ensuring a 0 or 1 return value.
Patch tested with FATE on x86-64, GNU/Linux by forcing the compatibility
code via an ifdef hack suggested by Michael.
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
It is known that the naive sqrt(x*x + y*y) approach for computing the
hypotenuse suffers from overflow and accuracy issues, see e.g
http://www.johndcook.com/blog/2010/06/02/whats-so-hard-about-finding-a-hypotenuse/.
This adds hypot support to FFmpeg, a C99 function.
On platforms without hypot, this patch does a reaonable workaround, that
although not as accurate as GNU libm, is readable and does not suffer
from the overflow issue. Improvements can be made separately.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
isnan and isinf are actually macros as per the standard. In particular,
the existing implementation has incorrect signature. Furthermore, this
results in undefined behavior for e.g double values outside float range
as per the standard.
This patch corrects the undefined behavior for all usage within FFmpeg.
Note that long double is not handled as it is not used in FFmpeg.
Furthermore, even if at some point long double gets used, it is likely
not needed to modify the macro in practice for usage in FFmpeg. See
below for analysis.
Getting long double to work strictly per the spec is significantly harder
since a long double may be an IEEE 128 bit quad (very rare), 80 bit
extended precision value (on GCC/Clang), or simply double (on recent Microsoft).
On the other hand, any potential future usage of long double is likely
for precision (when a platform offers extra precision) and not for range, since
the range anyway varies and is not as portable as IEEE 754 single/double
precision. In such cases, the implicit cast to a double is well defined
and isinf and isnan should work as intended.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
The emulation is unused and causes compilation trouble on systems
where fminf() is defined in <math.h> but missing from libm.
This should fix compilation on Debian powerpcspe.
This avoids issues when the FFMIN parameter evaluation has side effects
Reviewed-by: Clément Bœsch <u@pkh.me>
Reviewed-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
The function is known to be missing in at least one target (MSVC).
Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
* commit '80521c1997a23e148edf89e11b939ab8646297ca':
build: allow targets to specify extra objects to link with executables
swscale: avoid pointless use of compound literals
libm: add fallbacks for various single-precision functions
network: use getservbyport() only if available
network: add fallbacks for INADDR_LOOPBACK and INET_ADDRSTRLEN
Include sys/time.h before sys/resource.h
Conflicts:
Makefile
configure
libavutil/libm.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
configure: Check for the math function rint
TechSmith Screen Codec 2 decoder
rtsp: Add listen mode
rtsp: Make rtsp_open_transport_ctx() non-static
rtsp: Move rtsp_read_close
rtsp: Parse the mode=receive/record parameter in transport lines
Conflicts:
Changelog
libavcodec/avcodec.h
libavcodec/version.h
libavformat/version.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
mss1: validate number of changeable palette entries
mss1: report palette changed when some additional colours were decoded
x86: fft: replace call to memcpy by a loop
udp: Support IGMPv3 source specific multicast and source blocking
dxva2: include dxva.h if found
libm: Provide fallback definitions for isnan() and isinf()
tcp: Pass NULL as hostname to getaddrinfo if the string is empty
tcp: Set AI_PASSIVE when the socket will be used for listening
Conflicts:
configure
libavcodec/mss1.c
libavformat/udp.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
avconv: add an assert to silence an uninitialized variable warning.
avconv: shut up an uninitialized variable warning.
avfiltergraph: shut up uninitialized variable warning.
af_join: initialize a variable to shut up gcc warning.
amix: fix format specifier for AVFilterLink.sample_rate.
lavfi: make filters less verbose.
mpc8: read APE tags.
lavr: x86: fix ff_conv_fltp_to_flt_6ch function prototypes
libm: provide fallback definition for cbrtf() using powf()
network: Don't redefine error codes if they already exist in errno.h
configure: Check for sys/time.h
network: Include unistd.h from network.h
avconv: don't include vsrc_buffer.h, which doesn't exist anymore
lavfi: reorder AVFilterLink fields.
lavfi: reorder AVFilterContext fields.
lavfi: reorder AVFilter fields.
lavfi: reorder AVFilterBufferRef fields.
lavfi: reorder AVFilterBuffer fields.
Conflicts:
configure
libavcodec/v210dec.h
libavfilter/asrc_anullsrc.c
libavfilter/avfilter.h
libavfilter/buffersrc.c
libavfilter/src_movie.c
libavfilter/vf_aspect.c
libavfilter/vf_crop.c
libavfilter/vf_drawbox.c
libavfilter/vf_fade.c
libavfilter/vf_overlay.c
libavfilter/vf_pad.c
libavfilter/vf_scale.c
libavfilter/vsrc_color.c
libavformat/network.h
libavutil/libm.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
This adds a fallback for cbrtf() using powf(x, 1/3). Since
powf() with a non-integer exponent requires a non-negative
base, special handling of negative inputs is needed.
Signed-off-by: Mans Rullgard <mans@mansr.com>
AMR NB and WB decoders are optimized for MIPS architecture.
Appropriate Makefiles are changed accordingly.
Cnfigure script is changed in order to support optimizations.
Optimizations are enabled by default when compiling is done for
mips architecture.
Appropriate cflags are automatically set.
Support for several mips CPUs is added in configure script.
New ffmpeg options are added for disabling optimizations.
The FFMPEG option --disable-mipsfpu disables MIPS floating point
optimizations.
The FFMPEG option --disable-mips32r2 disables MIPS32R2
optimizations.
The FFMPEG option --disable-mipsdspr1 disables MIPS DSP ASE R1
optimizations.
The FFMPEG option --disable-mipsdspr2 disables MIPS DSP ASE R2
optimizations.
Signed-off-by: Nedeljko Babic <nbabic@mips.com>
Reviewed-by: Vitor Sessak <vitor1001@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
* qatar/master:
APIChanges: document git revision for CODEC_CAP_SLICE_THREADS addition.
Introduce slice threads flag.
FATE: allow forcing thread-type when doing threaded fate runs.
Use av_log_ask_for_sample() where appropriate.
error: sort, pack, and align error code and string definitions
The stabilization period after version bumps should be one month, not one week.
applehttp: Expose the stream bitrate via metadata
doc: Add some initial docs on the applehttp demuxer
Provide a fallback version of the libm function trunc
libavdevice: Define _XOPEN_SOURCE for usleep
lavc: provide deprecated avcodec_thread_init until next major version
lavc: provide the opt.h header until the next bump
error: change AVERROR_EOF value
error: remove AVERROR_NUMEXPECTED
error: add error code AVERROR_OPTION_NOT_FOUND, and use it in opt.c
Conflicts:
libavcodec/h264.c
libavutil/error.c
libavutil/error.h
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Passing an explicit filename to this command is only necessary if the
documentation in the @file block refers to a file different from the
one the block resides in.
Originally committed as revision 22921 to svn://svn.ffmpeg.org/ffmpeg/trunk
ffmpeg.c uses lrintf(), which is missing on some systems. Previously
it picked up the replacement via libavutil/internal.h due to
HAVE_AV_CONFIG_H being erroneously defined.
Moving these replacements to a separate header enables ffmpeg.c to
use them without being exposed to internal interfaces.
This use of a non-public header is justified by the header in question
not being part of the internal interface either. It should rather be
considered as part of the build system, which is shared between the
libraries and the applications.
This header cannot be installed since the tested conditions depend on
the compiler.
Originally committed as revision 22399 to svn://svn.ffmpeg.org/ffmpeg/trunk
