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Some clarifications (actually MIPS doesn't implement the float DCT/IDCT using SIMD instructions)

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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.4.x@1517 632fc199-4ca6-4c93-a231-07263d6284db
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DRC
2015-01-16 07:16:53 +00:00
parent 3af282df3c
commit c60d662ee4
2 changed files with 10 additions and 11 deletions
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17
Makefile.am
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@@ -440,17 +440,18 @@ endif
# The output of the floating point tests is not validated by default, because
# the output differs depending on the type of floating point math used, and
# this is only deterministic if there is full SIMD coverage of all of the
# floating point algorithms in libjpeg-turbo. Pass one of the following on the
# make command line to validate the floating point tests against one of the
# expected results:
# this is only deterministic if the DCT/IDCT are implemented using SIMD
# instructions on a particular platform. Pass one of the following on the make
# command line to validate the floating point tests against one of the expected # results:
#
# FLOATTEST=sse validate against the expected results from the libjpeg-turbo
# SSE SIMD extensions
# FLOATTEST=32bit validate against the expected results from the MIPS DSPr2
# SIMD extensions or 32-bit FPUs or GCC when -mfpmath=sse is
# used (which is the default on x86-64 systems)
# FLOATTEST=64bit validate against the exepected results from 64-bit FPUs
# FLOATTEST=32bit validate against the expected results from the C code
# when running on a 32-bit FPU (or when SSE is being used for
# floating point math, which is generally the default with
# x86-64 compilers)
# FLOATTEST=64bit validate against the exepected results from the C code
# when running on a 64-bit FPU
# CC: RGB->YCC SAMP: fullsize/int FDCT: float ENT: prog huff
./cjpeg -sample 3x2 -dct float -prog -outfile testout_3x2_float_prog.jpg $(srcdir)/testimages/testorig.ppm

4
README-turbo.txt
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@@ -313,9 +313,7 @@ following reasons:
range of the quality scale is typically more like a 1.0 dB difference.)
-- If the floating point algorithms in libjpeg-turbo are not implemented using
SIMD instructions on a particular platform, then the accuracy of the
floating point DCT/IDCT can depend on the compiler settings. For instance,
different results will be obtained when using -mfpmath=387 or -mfpmath=sse
with GCC on x86 systems.
floating point DCT/IDCT can depend on the compiler settings.
While libjpeg-turbo does emulate the libjpeg v8 API/ABI, under the hood, it is
still using the same algorithms as libjpeg v6b, so there are several specific