Re: How to write optimized code for an instruction set not supported by my computer?

From	Mario Castelán Castro <marioxcc.MT@yandex.com>
Newsgroups	linux.debian.user
Subject	Re: How to write optimized code for an instruction set not supported by my computer?
Date	2015-11-14 02:20 +0100
Message-ID	<quxFw-5CH-3@gated-at.bofh.it> (permalink)
References	<qrBmh-4ms-3@gated-at.bofh.it> <qsH6i-6m1-5@gated-at.bofh.it> <quxma-5g3-3@gated-at.bofh.it>
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El 13/11/15 a las 18:50, Joel Rees escribió:
> On Mon, Nov 9, 2015 at 7:54 AM, Mario Castelán Castro
> <marioxcc.MT@yandex.com> wrote:
>> [...]
>> joel.rees@gmail.com writes:
>>>
>>> The question being begged is this -- Do you really want to use AVX
>>> enough to sign the Intel agreement that you can't read unless you
>>> agree to it before you read it so you can download it and read it?
>>>
>>> It *is* a valid question, and I can't tell you the answer to that.
>>> Maybe you can't answer that question yourself yet.
>>
>>
>> No, I am not willing to use Intel's proprietary tools. In an earlier message
>> in the same thread I said that I avoid proprietary software. That is one of
>> the reasons of why I use Debian: It is easy to avoid the proprietary
>> software.
>
> Might I suggest you question (in addition to the questions about
> actual performance benefits) whether dealing with Intel's hardware
> licensing is significantly less onerous than dealing with their
> software licensing. Also whether you can actually escape the software
> licensing if you start developing to their hardware.
>
> AVX is a minefield.

Minefield in what regard?. What do you mean by "Intel's hardware 
licensing"?.

If you mean licensing the patents that are required to *implement* the 
instruction set, bear in mind that I am not doing that: I am not 
designing nor implementing a CPU. AFAIK, no license is required to 
_write a program_ that uses some instruction set. I have never heard 
that a compiler, assembler, or program written partially in assembly had 
to acquire a license.

>> Thanks to everybody who replied. I will probably use Bochs when time comes
>> to port the algorithm to AVX. Right now I am writing and perfecting it in
>> portable C, to have a base result against which to compare performance and
>> complexity.
>>
>> Regards.
>>
>
> This is definitely the recommended course. Also check the time spent
> in conversion with the time spent in data extraction and storing, etc.

Sure. I have already made a trivial variation of my Base64 encoding code 
that does no conversion, only copies the data. I use this for 
comparison. I also compare speed against memcpy to have an idea of what 
the overhead against just copying is (taking into account that the data 
expands during encoding, some of the input data is duplicated into the 
output when using memcpy to make the comparison more fair).

Thanks.

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