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<p>Hi Hugh,</p>
<p><br>
</p>
<p>My guess is that this patch will work for simple cases, but would
break correlation in cases where different antennas have different
numbers of channels or when zoom bands are used or when multiple
datastreams are used for an antenna. I think you will need to
find a different way to get the number of channels appropriate for
the particular datastream. I don't know which function that would
be (if it exists). Maybe Adam happens to know?</p>
<p><br>
</p>
<p>-Walter<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 5/30/25 08:53, Hugh Garsden via
Difx-users wrote:<br>
</div>
<blockquote type="cite" cite="mid:LO0P265MB57638DA01318F7DFB5926593AE61A@LO0P265MB5763.GBRP265.PROD.OUTLOOK.COM">
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Hi Walter,</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">
<span style="color: rgb(0, 0, 0);">The fix is simple but I had
to figure out how to get the inputChannelsPerThread, which
</span><span style="color: black;">setvdifmuxinputchannels() needs.
I decided to get it from the VEX file not the VDIF file
because (I think) we want to check the VDIF file against what
is specified in the VEX. </span></div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: black;">
<br>
</div>
<div class="elementToProof" style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: black;">
The file mpifxcorr/src/vdifnetwork.cpp is where the vmux is
configured for VDIF using configurevdifmux(). I added the call
to setvdifmuxinputchannels() immediately after that. Here is the
diff:</div>
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<br>
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<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
===================================================================</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
--- mpifxcorr/src/vdifnetwork.cpp (revision 11112)</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
+++ mpifxcorr/src/vdifnetwork.cpp (working copy)</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
@@ -344,7 +344,11 @@</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
cfatal << startl << "configurevmux
failed with return code " << rv << endl;</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
MPI_Abort(MPI_COMM_WORLD, 1);</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
}</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
+ if ( setvdifmuxinputchannels(&vm,
config->getFreqTableLength()) != 0 ) {</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
+ cfatal << startl <<
"setvdifmuxinputchannels failed" << endl;</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
+ MPI_Abort(MPI_COMM_WORLD, 1);</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
+ }</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
fanout = config->genMk5FormatName(format,
nrecordedbands, bw, nbits, sampling, vm.outputFrameSize,
config->getDDecimationFactor(configindex, streamnum),
config->getDAlignmentSeconds(configindex, streamnum),
config->getDNumMuxThreads(configindex, streamnum),
formatname);</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
if(fanout != 1)</div>
<div style="margin-left: 40px; font-family: "Courier New", monospace; font-size: 10pt; color: black;" class="elementToProof">
{</div>
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<br>
</div>
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Note I am using DiFX-2.8.1 downloaded via SVN not git.</div>
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<br>
</div>
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<br>
</div>
<div style="margin-left: 0px; font-family: "Aptos", "Aptos_EmbeddedFont", "Aptos_MSFontService", "Calibri", "Helvetica", sans-serif; font-size: 12pt; color: black;" class="elementToProof">
Hugh</div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b>
Difx-users <a class="moz-txt-link-rfc2396E" href="mailto:difx-users-bounces@listmgr.nrao.edu"><difx-users-bounces@listmgr.nrao.edu></a> on
behalf of Walter Brisken via Difx-users
<a class="moz-txt-link-rfc2396E" href="mailto:difx-users@listmgr.nrao.edu"><difx-users@listmgr.nrao.edu></a><br>
<b>Sent:</b> 21 May 2025 16:11<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:difx-users@listmgr.nrao.edu">difx-users@listmgr.nrao.edu</a>
<a class="moz-txt-link-rfc2396E" href="mailto:difx-users@listmgr.nrao.edu"><difx-users@listmgr.nrao.edu></a><br>
<b>Subject:</b> Re: [Difx-users] Multi-thread 4-bit VDIF fails
with 'vdifmux() failed with return code -2014' {External}
{External} {External}</font>
<div> </div>
</div>
<div>
<p>Hi Hugh,</p>
<p><br>
</p>
<p>It may have been oversight that led to the current code and
lack of support for your mode. Can you create a branch with
the implementation of your fix, or just sent a diff to the
list, and I can take a look?</p>
<p><br>
</p>
<p>I am pretty sure no one has actually ever used DiFX with VDIF
streams that are both multi-channel per thread and
multi-thread, so this may be new ground you are covering. In
theory it should be supported.<br>
</p>
<p><br>
</p>
<p>Thanks,</p>
<p><br>
</p>
<p>Walter<br>
</p>
<p><br>
</p>
<div class="x_moz-cite-prefix">On 5/21/25 08:57, Hugh Garsden
via Difx-users wrote:<br>
</div>
<blockquote type="cite">
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<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Hi all,</div>
<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Regarding Jake's message below, difx is using multiplexing
to combine multiple threads into a single thread. However it
can only deal with 1 channel per input thread because that
is hardwired in the code. Here:
<a href="https://urldefense.com/v3/__https://github.com/difx/difx/blob/c2ac995454fa96de38c651f6eea484b4a5db73ca/libraries/vdifio/src/vdifmux.c*L150__;Iw!!PDiH4ENfjr2_Jw!GKpKkvu39hHk0v0fSLpyefSUwep7WvZzidPuv9nndJiLPv2q5yJE6hIh9yBgvCN-tErCoIU8vbAh3zs19yNSkb6EJWWsrDXxwg5o$" id="OWAc5ea3557-12e4-1262-23d6-bd219c0c32b0" class="x_OWAAutoLink x_moz-txt-link-freetext" moz-do-not-send="true"><font color="red"><b>MailScanner has detected a possible fraud attempt from "urldefense.com" claiming to be</b></font> <font color="red"><b>MailScanner
has detected a possible fraud attempt from
"urldefense.com" claiming to be</b></font> <font color="red"><b>MailScanner has detected a possible fraud
attempt from "urldefense.com" claiming to be</b></font>
https://github.com/difx/difx/blob/c2ac995454fa96de38c651f6eea484b4a5db73ca/libraries/vdifio/src/vdifmux.c#L150
[github.com]</a>. The way to change that is mentioned in
comment, which is to call setvdifmuxinputchannels(). That's
what the vmux program does, and it works ok. I'm wondering
why difx doesn't do that, and maybe there should be a
warning about it not doing that. Anyway, that line of code
is in configurevdifmux() so I've added a call to
setvdifmuxinputchannels() after configurevdifmux() is called
in difx, and now the multiplexing is working with more than
1 channel.</div>
<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Hugh</div>
<div class="x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Difx-users
<a class="x_moz-txt-link-rfc2396E" href="mailto:difx-users-bounces@listmgr.nrao.edu" moz-do-not-send="true">
<difx-users-bounces@listmgr.nrao.edu></a> on
behalf of Jacob Brooks via Difx-users
<a class="x_moz-txt-link-rfc2396E" href="mailto:difx-users@listmgr.nrao.edu" moz-do-not-send="true"><difx-users@listmgr.nrao.edu></a><br>
<b>Sent:</b> 20 February 2025 12:12<br>
<b>To:</b> <a class="x_moz-txt-link-abbreviated moz-txt-link-freetext" href="mailto:difx-users@listmgr.nrao.edu" moz-do-not-send="true">
difx-users@listmgr.nrao.edu</a> <a class="x_moz-txt-link-rfc2396E" href="mailto:difx-users@listmgr.nrao.edu" moz-do-not-send="true">
<difx-users@listmgr.nrao.edu></a><br>
<b>Subject:</b> [Difx-users] Multi-thread 4-bit VDIF fails
with 'vdifmux() failed with return code -2014' {External}</font>
<div> </div>
</div>
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<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Hi all,</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
We're currently trying to get DiFX working with the
following setup: 4-bit, 2 channel (L + R pols), 2 threads
(2 subbands), delivered in real time via UDP. It has been
working fine up until the point where we tried adding a
second thread - single-thread VDIF has been working for
us.<br>
<br>
When running in multi-threaded mode, the datastream
processes crash with the following message:<br>
<br>
'vdifmux() failed with return code -2014, likely input
buffer is too small!'<br>
<br>
I have managed to trace the problem to a check in
'getLowestFrameNumber' in vdifio/src/vdifmux.c. The
inequality check in that function:<br>
<br>
'getVDIFNumChannels(vh) != vm->inputChannelsPerThread'</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
succeeds as the function returns a value of 2 while
'inputChannelsPerThread' has a value of 1. This happens
for every iteration so vdifmux() fails and returns a -2014
error code.</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
I'm not sure where to go from here and was hoping someone
more familiar with DiFX could help out. Hopefully I'm not
missing something obvious! If you need any more
information I haven't provided please do ask.</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
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Cheers,</div>
<div class="x_x_elementToProof" style="font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif; font-size:12pt; color:rgb(0,0,0)">
Jake</div>
</div>
<br>
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