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<TITLE>Release Notes for LDPC-codes Software</TITLE>
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<H1>Release Notes for LDPC-codes Software</H1>
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These notes describe all the stable public releases of this software. Old
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and future releases can be obtained via
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<BLOCKQUOTE>
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<A HREF="http://www.cs.toronto.edu/~radford/ldpc.software.html">
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<TT>http://www.cs.toronto.edu/~radford/ldpc.software.html</TT></A>
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</BLOCKQUOTE>
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The current development version is now maintained at
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<BLOCKQUOTE>
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<A HREF="http://github.com/radfordneal/LDPC-codes">
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<TT>http://github.com/radfordneal/LDPC-code</TT></A>
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</BLOCKQUOTE>
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<H2>Version of 2012-02-11.</H2>
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This version has a few bug fixes and some minor new features. The major
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change is that a source repository for the software is now hosted
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at github.com, making it easier for people to create and release
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their own versions of this software.
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<OL>
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<LI> Changed the copyright notice (in the file COPYRIGHT, and elsewhere)
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to remove the requirement that my web site be referenced. (Nowadays,
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I think users should have no problem finding the sources using a
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search engine.)
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<LI> Included a copy of the nrand48 routine from the GNU C library
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in the rand.c module, to ensure that it is always available
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and always the same. (This isn't so on some versions of cygwin.)
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<LI> Added a -f option to encode and decode that forces flushing
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after writing each block. Useful for allowing encode or
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decode to be used as a server, reading and writing blocks
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from named pipes.
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<LI> Added a -z option for pchk-to-alist to suppress output of 0
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row and column indexes that pad up to the maximum number used.
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<LI> Documented the previously undocumented -t options for pchk-to-alist
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and alist-to-pchk.
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<LI> Changed alist-to-pchk so that it no longer requires zero indexes
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that pad out to the maximum needed for a row or column (thanks
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to Monica Kolb for suggesting this).
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<LI> Changed mod2word type in mod2dense.c to uint32_t, to avoid
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wasted space when long is 64 bits (thanks to Mathieu Cunche
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and Vincent Roca for suggesting this).
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<LI> Fixed bug in distrib.c affecting distributions with a single
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number (thanks to Mike Vicuna for pointing it out).
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<LI> Fixed bug in -t option for pchk-to-alist (thanks to Andrea Fontana
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for reporting this).
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<LI> Fixed references in the documentation to mod2sparse_multvec
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that should be to mod2sparse_mulvec (thanks to Andrea Fontana
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for reporting this).
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</OL>
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<H2>Version of 2006-02-08.</H2>
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The copyright notice has been changed in this release to no longer
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restrict use to purposes of research or education. The new copyright
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notice can be read <A HREF="index.html#copyright">here</A>. It is now
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possible to create LDPC codes with varying numbers of checks per bit
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(an extension based on work by Peter Junteng Liu). New programs for
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converting to and from the <A
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HREF="http://www.inference.phy.cam.ac.uk/mackay/codes/alist.html">alist
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format</A> for parity check matrices, used by David MacKay and others,
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have also been added.
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<P>The following new features have been added:
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<OL>
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<LI> The <A HREF="pchk.html#make-ldpc"><TT>make-ldpc</TT></A> program can
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new create LDPC codes with varying numbers of checks per bit. The
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<A HREF="examples.html">examples</A> now include a code of this sort.
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<LI> New programs <A HREF="pchk.html#pchk-to-alist"><TT>pchk-to-alist</TT></A>
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and <A HREF="pchk.html#alist-to-pchk"><TT>alist-to-pchk</TT></A> have
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been added, which convert to and from <A
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HREF="http://www.inference.phy.cam.ac.uk/mackay/codes/alist.html">alist
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format</A>.
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<LI> A <A HREF="run-examples"><TT>run-examples</TT></A> script has been
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added, which runs all the <A HREF="examples.html">examples</A> and
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compares with the saved output that I obtained.
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</OL>
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<H2>Version of 2001-11-18.</H2>
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This is a minor release, whose main purpose is fixing bug (1) below.
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Also, this release has been tested and found to work with the <A
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HREF="http://www.cygwin.com">cygwin</A> Unix environment that runs
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under Microsoft Windows.
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<P>The following new feature has been added:
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<OL>
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<LI> A new <B>-t</B> option has been added to
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<A HREF="pchk.html#print-pchk"><TT>print-pchk</TT></A>, which
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causes it to print the transpose of the parity check matrix.
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</OL>
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The following program module change was made:
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<OL>
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<LI> The behaviour of <A
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HREF="mod2dense.html#invert_selected">mod2dense_invert_selected</A>
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has been changed when the matrix has dependent rows. The result returned
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contains the inverse of a sub-matrix in its initial columns. The contents
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of the remaining columns up to the number of rows was previously undefined,
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but these columns are now set to contain zeros. This was done to fix
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bug (1) below.
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</OL>
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The following bugs were fixed:
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<OL>
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<LI> A bug has been fixed in
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<A HREF="encoding.html#make-gen"><TT>make-gen</TT></A>
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which sometimes
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produced invalid `dense' or `mixed' generator matrices when the parity
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check matrix had redundant rows.
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The `sparse' generator matrices were not affected. The output of the
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<A HREF="ex-dep"><TT>ex-dep</TT></A> example has changed slightly as a
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result.
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<LI> The open mode for reading the file of random numbers has been changed from
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"r" to "rb", for compatibility with non-Unix systems.
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<LI> <A HREF="mod2sparse.html#copy"><TT>mod2sparse_copy</TT></A> has
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been fixed so that it copies the <B>lr</B> and <B>pr</B> fields
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of entries.
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<LI> The "set -v -e" in the command files for the examples has
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been replaced by two commands, "set -e" and "set -v", since some
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shells can't set two options at once.
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</OL>
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A few minor fixes to the documentation have also been made.
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<H2>Version of 2001-05-04.</H2>
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Changes and new features regarding programs and associated
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documentation and examples:
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<OL>
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<LI> Warnings have been added to the documentation about the dangers of
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using zero codewords for testing (due to the possibility of the decoder
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accidently being non-symmetric). The examples have been changed to
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not use zero codewords, except for
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<A HREF="ex-ham7a"><TT>ex-ham7a</TT></A>, which still
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demonstrates this facility.
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<LI> Decoding by probability propagation has been changed so that if
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a probability ratio gets set to NaN ("not a number", the result of
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infinite but conflicting evidence from different sources), the probability
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ratio is changed to 1, in hopes that something sensible may result.
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<LI> The decoding procedures have been changed to decode a bit to a 1 if
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there is a tie, so that any resulting asymmetry in decoding will
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make zero decoding less, rather than more, likely. See point (1) above.
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<LI> All programs now allow a file name argument to be "-", which specifies
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standard input or standard output, as appropriate. The
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<A HREF="ex-ldpc36-5000a"><TT>ex-ldpc36-5000a</TT></A> example has been
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changed to use this facility in order to avoid creating lots of files.
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<LI> Channels with noise from a logistic distribution (AWLN) have been
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implemented. For details,
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see the <A HREF="channel.html">channel documentation</A>.
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<LI> The <B>make-gen</B> program for "dense" or "mixed" options was modified
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so that when some parity checks are redundant, others are not declared
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redundant when they aren't. This makes the result compatible with
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what is obtained with the "sparse" option. The example in the
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<A HREF="dep-H.html">discussion of linear dependence in parity check
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matrices</A> has changed slightly as a result.
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<LI> The messages displayed by the <A HREF="decoding.html#decode">decode</A>
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program have changed slightly: The block size is no longer displayed,
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and the percentage of bits changed is now shown. The data output
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when the <B>-t</B> option is specified now includes the number of
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bits changed in each block.
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<LI> A new <B>-T</B> option to <A HREF="decoding.html#decode">decode</A>
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for displaying
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<A HREF="decode-detail.html">detailed information on decoding</A>
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has been added.
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<LI> Doing a <B>make clean</B> will now remove the files created
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by running the <A HREF="examples.html">examples</A>.
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<LI> The files created by the <A HREF="examples.html">examples</A> now
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start with "<TT>ex-</TT>" and contain a ".", to make them easier to
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identify for cleanup, and the saved output file now ends in
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"<TT>-out</TT>" rather than "<TT>.out</TT>".
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<LI> The scripts for the examples now use the <B>-v</B> option of <B>set</B>
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rather than <B>-x</B>, so that the command lines are echoed
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faithfully as they are read.
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<LI> Two new <A HREF="examples.html">examples</A> have been added:
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<TT>ex-dep</TT> demonstrates what happens when parity check matrices
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have redundant row, and <TT>ex-wrong-model</TT> investigates what
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happens when the wrong model is used to decode.
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</OL>
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Changes and new features regarding program modules and other internals:
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<OL>
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<LI> Instructions have been added on
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<A HREF="modify.html">how to modify the programs</A>, and some
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code has been reorganized to facilitate modifications.
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<LI> The makefile has been made trivial, simply recompiling everything
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from scratch every time. This is simpler and less error prone
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than putting in dependencies.
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Compiling all the programs takes only about five seconds on a
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modern PC.
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<LI> The
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<A HREF="mod2dense.html#invert_selected"><TT>mod2dense_invert_selected</TT></A>
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procedure has been changed
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to take an additional argument in which a permutation of rows is
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returned. This extension is needed in order for the result when
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the matrix is not of full rank to include as many rows as possible,
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as needed for the above modification of <B>make-gen</B>.
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<LI> New routines
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<A HREF="mod2dense.html#copyrows"><TT>mod2dense_copyrows</TT></A> and
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<A HREF="mod2sparse.html#copyrows"><TT>mod2sparse_copyrows</TT></A> have
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been added, analogous to the previous routines for copying columns.
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<LI> The decoding procedures have been changed to always return the bit
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probabilities (previously, one could pass a null pointer to suppress
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this). This makes things simpler, and facilitates the production of
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detailed trace output when the <B>-T</B> option is used.
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</OL>
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The following bugs were fixed:
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<OL>
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<LI> A problem with <B>print-gen</B> prevented the <B>-d</B> option from working
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in most cases. The documentation was also fixed to note what
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the <B>L</B> and <B>U</B> matrices printed will look like.
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<LI> The documentation for
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<A HREF="mod2sparse.html#copycols"><TT>mod2sparse_copycols</TT></A> and
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<A HREF="mod2dense.html#copycols"><TT>mod2dense_copycols</TT></A>
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was ambiguous. It has been clarified. The dense and sparse
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implementations were inconsistent. The sparse version has been changed
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to match the dense version, which was and is the only version actually
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used in the LDPC software.
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<LI> In <TT>decode.c</TT>, a variable declared to be <TT>float</TT> was printed
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using "<TT>%f</TT>", which strangely didn't work with one compiler.
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It's now declared as <TT>double</TT>.
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</OL>
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There were also numerous minor cleanups of program code and documentation.
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<H2>Version of 2000-03-19.</H2>
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This was the first public release.
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<HR>
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<A HREF="index.html">Back to index for LDPC software</A>
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</BODY></HTML>
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