|Re: [eigen] State of eigen support for small integers(16 bit, signed/unsigned)|
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- Subject: Re: [eigen] State of eigen support for small integers(16 bit, signed/unsigned)
- From: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
- Date: Thu, 20 Aug 2009 09:45:34 -0400
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2009/8/20 Rohit Garg <rpg.314@xxxxxxxxx>:
> What is the state of eigen's support for small integers(16 bit,
> signed/unsigned). I had a look at the branch over at bitbucket, and
> there doesn't seem to be any small int specific patches in it.
> Any body care to comment on the state of this branch?
Only Patrick can comment on his own branch;)
> If I need to add support for small ints to eigen, what do I need to
> do? I need all bitwise ops, and yes, 16 bit*16 bit = 32 bit unsigned
> integer multiplication (vectorized of course). Suggestions?
First, read this,
The two most important things are to edit the files NumTraits.h and
MathFunctions.h in Core/.
For vectorization, you'll have to edit the files in Core/arch/... at
least Core/arch/SSE/PacketMath.h. Not sure about how it works for
small ints (are there specific SSE instructions for e.g. adding two
packets of 8 int16's ? you know better than me)
For the bitwise ops, in the non-vector case i don't think you need to
do anything special since operators & |... work natively; you can
always check the Functors.h either in Core/ or in Array/ ; for
vectorization I'm very optimistic too -- we already have ei_pand(),
ei_por() etc in PacketMath.h and since for bitwise ops the integer
size is irrelevant, you should be able to use that.
> BTW, are such features even welcome in eigen?
Yes, most welcome. When I look at forums linking to our website, this
is a frequently wanted feature. The fact that people on this list
asked for it several times, finishes proving that it's a wanted
feature. Vectorization is most welcome here too -- the prospect of 8x
boosts on int16 and 16x boosts on int8 is very interesting...