Re: [Discuss-gnuradio] VOLK: fast way to log10()?

[Marcus Müller]

By the way, with a bit of approximation and a little acceptance for
errors in corner cases, log2 of a IEEE-754 float is simply it's exponent
+ log2(mantissa), with the later potentially being implementable using
lookup tables.
Also, VOLK does have a log2, kernel, volk_32f_log2_32f

Best regards,
Marcus

On 16.09.2015 06:50, Brian Padalino wrote:
> On Wed, Sep 16, 2015 at 12:24 AM, Dennis Glatting <address@hidden> wrote:
>> 1) Working with VOLK to learn VOLK.
>> 2) Having fun with vectors.
>> 3) Generating power data points for plotting across a selected
>>    set of samples.
> Lastly, another alternative, if you wanted to utilize what is already
> there in VOLK, if you wanted to do something like 10*log10(x), you can
> also think of it as 10*log2(x)/log2(10) - rewritten to put the
> constants together - 10*log2(10)*log2(x), where 10*log2(10) is
> 3.01029995664.
>
> So convert a vector of floats into log2 then multiply a vector by a
> const that is equal to 10*log2(10) to get them to their final value.
> Not as efficient, potentially, but still an option if you want to
> learn VOLK.
>
> Brian
>
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