Re: [Discuss-gnuradio] GNU Radio release 3.6.3 available for download

[Tom Rondeau]

On Wed, Jan 23, 2013 at 10:43 AM, Michael Dickens <address@hidden> wrote:

On Jan 23, 2013, at 10:34 AM, Tom Rondeau <address@hidden> wrote:
>> On Wed, Jan 23, 2013 at 10:29 AM, Michael Dickens <address@hidden> wrote:

>> I'm wondering what "volk_profile" is doing?  It looks like it's running through (all?) available kernels for a given algorithm and finding the "best" (fastest?) one.  Is this correct?
>>
> Yes, that's correct. It runs each proto-kernel available on your machine and compares how long it took to execute them, then it stores the fastest version in the config file. This is then read when your program initializes a new VOLK kernel to find the right one to use.

Ah; OK.  Sort of like what FFTW does for fft's, but probably with its own twist.  So if the "volk_config" file exists, VOLK reads it and uses it to determine which kernel to use for a given VOLK algorithm instantiation.  [Is there a proper VOLK-like name for a "VOLK algorithm instantiation"?]  If this file does not exist, how does VOLK pick the kernel?  Is this info somewhere in a Wiki?  I haven't looked, so forgive me if I'm asking FAQ's. - MLD

We call the "VOLK algorithm instantiations" VOLK proto-kernels.

When the volk_config file doesn't exist or if it does not contain a reference to the kernel (say you've installed a new version and did not update your profile), then VOLK takes the set of proto-kernels that your machine can run and selects the 'highest' version. So ACX > SSE4 > SS2 > MMX, etc. While this isn't always the best kernel to use on a given machine, it's definitely the best way to select barring other information.

Will have to check the wiki to see how complete it currently is. Also, we just published a paper describing VOLK at the SDR conference. I should upload that to the website.

Tom