<div dir="ltr"><div><font face="arial, sans-serif">The meeting is tomorrow, Tuesday, April 4, 17-18 Helsinki time, 8-9 AM New York time.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">The topics / decisions of interest are:</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">A. Integer constants</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">We have constants that must be powers of two (mode constants), constants that must have a < relationship (error codes and thread levels), constants that should be negative to avoid conflicting with e.g. ranks, and constants that can be anything.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">I have a proposal for constants here: <a href="https://github.com/mpiwg-abi/specification-text-draft/blob/main/IntegerConstants.md">https://github.com/mpiwg-abi/specification-text-draft/blob/main/IntegerConstants.md</a>. I have not yet implemented Dan's suggestion to make constants unique (presumably, for the aforementioned categories that allow it).</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">I would like feedback on the following:</font></div><div><font face="arial, sans-serif">1. Are the values of MPI_MAX_*** acceptable? In all cases, I chose the greater of MPICH and OMPI. For MPI_BSEND_OVERHEAD, I used 512 to be safe. Is that too large? Is 128 better?</font></div><div><font face="arial, sans-serif">2. Are there any opponents to Dan's suggestion that all the constants are unique, within reason? If the consensus favors this, I'll redo all the constants accordingly.</font></div><div><font face="arial, sans-serif">3. Are there any other integer constant values that bother people? I have very little attachment to any of them, and it is trivial to change them now.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">B. Handle constants</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">I implemented a Huffman code for these (</font><a href="https://github.com/mpiwg-abi/specification-text-draft/blob/main/HandleConstants.md">https://github.com/mpiwg-abi/specification-text-draft/blob/main/HandleConstants.md</a>)<span style="font-family:arial,sans-serif">. I made a Python <a href="https://github.com/mpiwg-abi/specification-text-draft/blob/main/print-handle-constants.py">code</a> that implements it, and the program dumps all the values, and can be modified easily to generate mpi_abi.h.</span></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">Does anyone oppose the idea of a Huffman code? I know Hui is indifferent, which is obviously fine. One can ignore the Huffman code and just view the results as some random values I chose :-)</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">If you like Huffman codes, but dislike mine, then please complain soon. There are some parts that I do not love. For example, fixed size types are handled consistently and encode their size (as the log_2 of bytes) in bits 3:5, while language default types are on a different branch and encode their size in bits 8:10. I can makes those consistent, but it means the code branches aren't sequential in the bit indices. I think that's fine, but I am new to Huffman codes.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">An alternative to the above is to say that in mpi_abi.h, that MPI_INT, MPI_LONG and MPI_LONG_LONG are aliased to MPI_INTn_T according to the ABI definition, and do not exist on their own. This has some appeal, but will change the results of MPI_Type_get_name. What do people think about this?</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">The good news is there is lots of free space in the Huffman code for new handle types and new constants. I am not worried about running out of space. Already, I have reserved space for a bunch of types that are likely to exist in C and C++ in the near future, so those will be trivial to add later.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">Finally, as noted on Slack, we have to figure out whether we reserve space for or standardize some types that OMPI defines today in the MPI_ namespace. This is the lowest priority for me right now, so if we don't address it this week, that is fine.</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">Thanks,</font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">Jeff</font></div><div><font face="arial, sans-serif"><br></font></div><div><p class="MsoNormal" style="margin:0cm;font-size:11pt"><font face="arial, sans-serif"><span style="font-size:18pt;color:rgb(37,36,36)">Microsoft Teams
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<font face="arial, sans-serif"><span style="font-size:11pt;color:rgb(95,95,95)"><span style="opacity:0.36">____________________________________________</span></span><br></font></div><div><font face="arial, sans-serif"><br></font></div><font face="arial, sans-serif"><br clear="all"></font><div><font face="arial, sans-serif"><br></font></div><font face="arial, sans-serif"><span class="gmail_signature_prefix">-- </span><br></font><div dir="ltr" class="gmail_signature"><font face="arial, sans-serif">Jeff Hammond<br><a href="mailto:jeff.science@gmail.com" target="_blank" style="">jeff.science@gmail.com</a><br><a href="http://jeffhammond.github.io/" target="_blank" style="">http://jeffhammond.github.io/</a></font></div></div>