INSTALLATION INSTRUCTIONS

To build and install the Viterbi decoder libraries, simply say

./configure
make
make install (as root)

This will put the libraries in /usr/local/lib, the include files in
/usr/local/include, and the manual page in /usr/local/man.

SIMD-ASSISTED VERSIONS

Four separate versions of each decoder are provided. One is in
portable C and should run on any system with the GCC compiler and
linker. Three more versions in assembler use the three Intel SIMD
(single instruction, multiple data) instruction sets: MMX, SSE and
SSE2. These SIMD-assisted versions yield dramatically better
performance than the portable C version and should be used whenever
possible.

The MMX (MultiMedia eXtension) instruction set was introduced on later
Pentium CPUs; it is also implemented on the Pentium II and most AMD
CPUs starting with the K6. SSE (SIMD Streaming Extensions) was
introduced in the Pentium III; AMD calls it "3D Now! Professional".
Intel introduced SSE2 on the Pentium 4; to my knowledge it has not yet
been implemented on any AMD CPU.

SSE support implies MMX support, while SSE2 support implies both SSE
and MMX support.

If the target system is IA32 (i.e., i386/i486/i586/i686), all four
versions of the decoder (portable C,MMX,SSE and SSE2) are
built. Additionally, the configure script determines which, if any, of
the three SIMD instruction sets (MMX/SSE/SSE2) are supported on the
local CPU and installs the "best" one as the default for both the
static and shared versions. If none of the SIMD instruction sets are
supported, the portable C version is installed as the default.

On non-IA32 targets only the portable C version is built.

Since the usual GNU-style target_cpu name (e.g., "i686") does not
indicate which SIMD instructions are supported (if any), the configure
script has to run local tests to determine this information. This
currently precludes cross-compilation of the package.

TESTING THE VITERBI DECODER LIBRARY

After running the ./configure script, optional tests can be run as
follows:

make tests
make alltests

"make tests" tests each decoder using the default library, verifying
correct operation and estimating decoding speed. These tests should
always succeed unless something is broken.

On a IA32 machine, "make alltests" tests all four versions of the
library. (On non-IA32 machines, "make alltests" is identical to "make
tests").  Because "make alltests" tries every available SIMD version,
whether or not the local CPU supports it, some of these tests may
fail. E.g., on a Pentium III, the portable C, MMX and SSE tests will
succeed while the SSE2 test will fail.

LINKING APPLICATIONS TO THE VITERBI DECODER LIBRARY

Specifying -lviterbi to the linker links with the default version as
determined by the configure script.  Unless the -static flag is also
specified to the loader, the shared version will be used.

This default can be overridden, for static linking only, as follows:

-lviterbi_port - portable C version
-lviterbi_mmx - MMX version
-lviterbi_sse - SSE version
-lviterbi_sse2 - SSE2 version

7 Dec 2001
Phil Karn, karn@ka9q.net