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<p>The segFault occurs with a call to a RSFECPlugin
primitive>>#primMultiplyPolySelfCoefficients:otherCoefficients:product:fieldSize:.
But the crash.dmp shows a RSErasureGaloisWithPlugin as the error
site. I am very confused as the call I am making in the FEC test
is to the RSFECPlugin, but the RSErasurePlugin is the one cited as
causing the segFault. I even removed the RSErasurePlugin from the
vm directory and this is still occurring.<br/>
</p>
<blockquote>
<p>RSFECGenericGFPolyWithPlugin>>#multiplyPoly: other<br/>
<br/>
| product |<br/>
(field = other field)<br/>
ifFalse: [RSErasureIllegalArgumentError signal:
'GenericGFPolys do not have same GenericGF field'].<br/>
(self isZero)<br/>
ifTrue: [^ field zero]<br/>
ifFalse: [other isZero ifTrue: [^ field zero]].<br/>
product := Array new: (self coefficients size + other
coefficients size - 1) withAll: 0.<br/>
<br/>
product := self primMultiplyPolySelfCoefficients: self
coefficients otherCoefficients: other coefficients product:
product fieldSize: field size.<br/>
<br/>
^ RSFECGenericGFPoly newField: field coefficients: product.<br/>
</p>
</blockquote>
Any assistance most welcome. This has me stumped.<br/>
<div class="moz-signature">---<br/>
Kindly,<br/>
Robert<br/>
<br/>
<br/>
</div>
<div class="moz-cite-prefix">On 5/31/21 3:43 PM, Robert Withers
wrote:<br/>
</div>
<blockquote type="cite" cite="mid:9efaa46d-bf63-9708-8063-aca4136fbf7f@pm.me">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<p>My previous email is awaiting approval as it is too big. I
attached a crash.dmp. Here is the email with a link to the crash
dump I placed on dropbox.</p>
<p>I implemented a set of 5 primitives for Polynomial math in the
RSFECPlugin class and added a RSFECGenericGFPolyWithPlugin to
call them. In testing FEC I get a segFault, but looking at the
Smalltalk stack dump it is happening in the RSErasurePlugin
which is not called by the RSFEC code. It looks like a DoIt and
I cannot find the offending code. Where can I look for a DoIt
that is calling RSErasure code when running RSFEC code? Here is
the smalltalk stack dump and I am attaching the crash.dmp file
[1].</p>
<blockquote>
<p> 0x7ffde5e6a1b0 I
RSErasureGaloisWithPlugin>galoisMultiply:by: 0xc7ed9d8:
a(n) RSErasureGaloisWithPlugin<br/>
0x7ffde5e6a220 I
RSErasureGaloisWithPlugin>generateMultiplicationTable
0xc7ed9d8: a(n) RSErasureGaloisWithPlugin<br/>
0x7ffde5e59df0 I RSErasureGaloisWithPlugin>initialize
0xc7ed9d8: a(n) RSErasureGaloisWithPlugin<br/>
0x7ffde5e59e20 M RSErasureGaloisWithPlugin
class(Behavior)>new 0x7fdeec8: a(n)
RSErasureGaloisWithPlugin class<br/>
0x7ffde5e59e60 I RSErasureGalois class>newGalois
0x6a89510: a(n) RSErasureGalois class<br/>
0x7ffde5e59e90 M UndefinedObject>DoIt 0x2de78e0: a(n)
UndefinedObject<br/>
</p>
</blockquote>
<p> []1 crash.zip - <a class="moz-txt-link-freetext" href="https://www.dropbox.com/s/qyq735yksmc4dbr/crash.zip?dl=0" moz-do-not-send="true">https://www.dropbox.com/s/qyq735yksmc4dbr/crash.zip?dl=0</a><br/>
</p>
<blockquote> </blockquote>
---<br/>
Kindly,<br/>
Robert
<div class="moz-signature">---<br/>
Kindly,<br/>
Robert<br/>
<br/>
<br/>
</div>
<div class="moz-cite-prefix">On 5/30/21 8:50 PM, Robert Withers
wrote:<br/>
</div>
<blockquote type="cite" cite="mid:8e0916a2-cacf-a08b-32e4-9dce40383a2f@pm.me">
<pre class="moz-quote-pre" wrap="">Hi Levente,
Thank you for having a look-see and letting me know your thoughts! It
makes sense what you are saying. so I think the only way to speed it up
is to embed the loops into primitives. I have 5 of 6 methods from Poly
that I am stuffing into the plugin. The #dividePoly: is a bit more
complicated, updating the remainder poly and so forth. I do not think a
Poly can be within a primitive. Hopefully, {product := Array new: size
withAll: 0} will work in translation. I fixed #initializeExpTable per
your suggestion.
Thanks!
---
Kindly,
Robert
On 5/30/21 8:18 PM, Levente Uzonyi wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Hi Robert,
I had a quick look at the plugin code. The operations you implemented in
the plugin are way too simple. The VM's JIT makes the smalltalk code run
faster, because it has the same operations implemented, and it can avoid
calling the overhead of calling the primitive many times. Hence the
slowdown.
For example, RSFECPlugin >> #primitiveAddOrSubtractby seems to implement
bitwise xor on two 32-bit unsigned values, but the arguments are always
0-255. The VM has primitive 16, which does bitwise xor and covers that
input range, so the JIT, combined with other operations can generate
machine code directly with that without jumping back and forth between
native code and smalltalk.
If you want a plugin to provide any noticable speedup, you need to do
more computation in a single primtiive call.
Levente
P.S.: I think, in RSFECGenericGC >> #initializeExpTable, the lines
x := x bitXor: primitive.
x bitAnd: (size - 1)]].
should read
x := (x bitXor: primitive) bitAnd: size - 1 ]].
</pre>
</blockquote>
</blockquote>
</blockquote>
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