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<HTML><HEAD><TITLE>Release Notes for LDPC Software</TITLE></HEAD><BODY><H1>Release Notes for LDPC Software</H1>These notes describe all the public releases of this software.  Oldand future releases can be obtained via<BLOCKQUOTE><A HREF="http://www.cs.toronto.edu/~radford/ldpc.software.html"><TT>http://www.cs.toronto.edu/~radford/ldpc.software.html</TT></A></BLOCKQUOTE><H2>Release of 2001-11-18.</H2>This is a minor release, whose main purpose is fixing bug (1) below.Also, this release has been tested and found to work with the <AHREF="http://www.cygwin.com">cygwin</A> Unix environment that runsunder Microsoft Windows.<P>The following new feature has been added:<OL><LI> A new <B>-t</B> option has been added to      <A HREF="pchk.html#print-pchk"><TT>print-pchk</TT></A>, which      causes it to print the transpose of the parity check matrix.</OL>The following program module change was made:<OL><LI> The behaviour of <A     HREF="mod2dense.html#invert_selected">mod2dense_invert_selected</A>     has been changed when the matrix has dependent rows.  The result returned      contains the inverse of a sub-matrix in its initial columns.  The contents     of the remaining columns up to the number of rows was previously undefined,     but these columns are now set to contain zeros.  This was done to fix     bug (1) below.</OL>The following bugs were fixed:<OL><LI> A bug has been fixed in      <A HREF="encoding.html#make-gen"><TT>make-gen</TT></A>     which sometimes      produced invalid `dense' or `mixed' generator matrices when the parity      check matrix had redundant rows.     The `sparse' generator matrices were not affected.  The output of the      <A HREF="ex-dep"><TT>ex-dep</TT></A> example has changed slightly as a      result.<LI> The open mode for reading the file of random numbers has been changed from     "r" to "rb", for compatibility with non-Unix systems.<LI> <A HREF="mod2sparse.html#copy"><TT>mod2sparse_copy</TT></A> has     been fixed so that it copies the <B>lr</B> and <B>pr</B> fields     of entries.<LI> The "set -v -e" in the command files for the examples has      been replaced by two commands, "set -e" and "set -v", since some      shells can't set two options at once.</OL>A few minor fixes to the documentation have also been made.<H2>Release of 2001-05-04.</H2>Changes and new features regarding programs and associateddocumentation and examples:<OL><LI> Warnings have been added to the documentation about the dangers of     using zero codewords for testing (due to the possibility of the decoder     accidently being non-symmetric).  The examples have been changed to     not use zero codewords, except for      <A HREF="ex-ham7a"><TT>ex-ham7a</TT></A>, which still     demonstrates this facility.<LI> Decoding by probability propagation has been changed so that if     a probability ratio gets set to NaN ("not a number", the result of      infinite but conflicting evidence from different sources), the probability      ratio is changed to 1, in hopes that something sensible may result.<LI> The decoding procedures have been changed to decode a bit to a 1 if     there is a tie, so that any resulting asymmetry in decoding will      make zero decoding less, rather than more, likely.  See point (1) above.<LI> All programs now allow a file name argument to be "-", which specifies     standard input or standard output, as appropriate.  The      <A HREF="ex-ldpc36-5000a"><TT>ex-ldpc36-5000a</TT></A> example has been     changed to use this facility in order to avoid creating lots of files.<LI> Channels with noise from a logistic distribution (AWLN) have been     implemented.  For details,     see the <A HREF="channel.html">channel documentation</A>.<LI> The <B>make-gen</B> program for "dense" or "mixed" options was modified      so that when some parity checks are redundant, others are not declared      redundant when they aren't.  This makes the result compatible with     what is obtained with the "sparse" option.  The example in the      <A HREF="dep-H.html">discussion of linear dependence in parity check      matrices</A> has changed slightly as a result.<LI> The messages displayed by the <A HREF="decoding.html#decode">decode</A>      program have changed slightly: The block size is no longer displayed,     and the percentage of bits changed is now shown.  The data output     when the <B>-t</B> option is specified now includes the number of     bits changed in each block.  <LI> A new <B>-T</B> option to <A HREF="decoding.html#decode">decode</A>      for displaying     <A HREF="decode-detail.html">detailed information on decoding</A>     has been added.<LI> Doing a <B>make clean</B> will now remove the files created      by running the <A HREF="examples.html">examples</A>.<LI> The files created by the <A HREF="examples.html">examples</A> now     start with "<TT>ex-</TT>" and contain a ".", to make them easier to      identify for cleanup, and the saved output file now ends in      "<TT>-out</TT>" rather than "<TT>.out</TT>".<LI> The scripts for the examples now use the <B>-v</B> option of <B>set</B>     rather than <B>-x</B>, so that the command lines are echoed      faithfully as they are read.<LI> Two new <A HREF="examples.html">examples</A> have been added:     <TT>ex-dep</TT> demonstrates what happens when parity check matrices     have redundant row, and <TT>ex-wrong-model</TT> investigates what     happens when the wrong model is used to decode.</OL>Changes and new features regarding program modules and other internals:<OL><LI> Instructions have been added on      <A HREF="modify.html">how to modify the programs</A>, and some     code has been reorganized to facilitate modifications.<LI> The makefile has been made trivial, simply recompiling everything     from scratch every time.  This is simpler and less error prone     than putting in dependencies.     Compiling all the programs takes only about five seconds on a      modern PC.<LI> The  <A HREF="mod2dense.html#invert_selected"><TT>mod2dense_invert_selected</TT></A>     procedure has been changed     to take an additional argument in which a permutation of rows is     returned.  This extension is needed in order for the result when     the matrix is not of full rank to include as many rows as possible,     as needed for the above modification of <B>make-gen</B>.<LI> New routines      <A HREF="mod2dense.html#copyrows"><TT>mod2dense_copyrows</TT></A> and      <A HREF="mod2sparse.html#copyrows"><TT>mod2sparse_copyrows</TT></A> have     been added, analogous to the previous routines for copying columns.<LI> The decoding procedures have been changed to always return the bit     probabilities (previously, one could pass a null pointer to suppress     this).  This makes things simpler, and facilitates the production of     detailed trace output when the <B>-T</B> option is used.</OL>The following bugs were fixed:<OL><LI> A problem with <B>print-gen</B> prevented the <B>-d</B> option from working     in most cases.  The documentation was also fixed to note what     the <B>L</B> and <B>U</B> matrices printed will look like.<LI> The documentation for      <A HREF="mod2sparse.html#copycols"><TT>mod2sparse_copycols</TT></A> and     <A HREF="mod2dense.html#copycols"><TT>mod2dense_copycols</TT></A>     was ambiguous.  It has been clarified.  The dense and sparse      implementations were inconsistent.  The sparse version has been changed     to match the dense version, which was and is the only version actually     used in the LDPC software.<LI> In <TT>decode.c</TT>, a variable declared to be <TT>float</TT> was printed     using "<TT>%f</TT>", which strangely didn't work with one compiler.       It's now declared as <TT>double</TT>.</OL>There were also numerous minor cleanups of program code and documentation.<H2>Old release of 2000-03-19.</H2>This was the first public release.<HR><A HREF="index.html">Back to index for LDPC software</A></BODY></HTML>
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