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August 04 2011
Music
the elles from 110320-110714 (solo)


August 3, 2011
At the end of an enjoyable 8 months of development...


Hooray! Thank you to my fine coworkers/coconspirators: Schwa, Christophe, Ollie, White Tie, Geoff, and all of the lovely people who helped test and gave valuable feedback. Schwa and White Tie did a fantastic job on the new web site, too, I must say. <3

Soon after posting the new website (thank you, git, for making that easy), and after grabbing a celebratory coffee, I noticed the web site was a bit slow. The CPU use was low (an Amazon EC2 instance), but on looking at the bandwidth graph I saw it was pushing a ridiculous amount of traffic (presumably saturating the link, even). After mirroring the downloads to a CDN (CloudFront), all was well. Thank you, Amazon. I'm very impressed with AWS/EC2/etc. It's good stuff.

8 Comments


July 27 2011
Music
louie (jam/rehearsal)


Jul 24 2011
It's the most wonderful time of the year

OK maybe after cherry season.

2 Comments


July 22 2011
Music
louie (jam/rehearsal)


July 14 2011
Fun with denormals

Something that often comes up when writing audio applications are things called "denormals". These are floating point numbers that are very small, so small in fact that for some reason CPU designers think they are quite rare (OK so they are), so the circuitry that processes them is very slow, when compared to that of a "normal" sized number.

If you read that (awful) explanation, and didn't understand it or care, I apologize, you can stop reading now because it will only get more boring and less intelligible.

We have made some common code to filter out these numbers, as many others no doubt have done:

// boring code omitted, see WDL/denormal.h for the full code
// WDL_DENORMAL_DOUBLE_HW() is a macro which safely gets you the high 32 bits of a double as an unsigned int.

static double WDL_DENORMAL_INLINE denormal_filter_double(double a)
{
  return (WDL_DENORMAL_DOUBLE_HW(&a)&0x7ff00000) ? a : 0.0;
}
The above code pretty simply looks at the exponent field of the double, and if it is nonzero, returns the double, otherwise it returns 0.

Recently it came to our attention that we actually needed to filter out larger numbers as well (when sending those numbers through a process such as a FFT, they would end up as denormals). If we pick a number around 10^-16 (not being picky about the exact cutoff), which has an exponent of 0x3C9, we can choose to filter when the expoenent field is under that value:
static double WDL_DENORMAL_INLINE denormal_filter_double_aggressive(double a)
{
  return ((WDL_DENORMAL_DOUBLE_HW(&a))&0x7ff00000) >= 0x3c900000 ? a : 0.0;
}
That was pretty much free (ok slightly larger code, I suppose). One nice thing that became apparent was that we could filter NaN and infinity values this way as well (exponent == 0x7FF), with only the cost of a single integer addition:
static double WDL_DENORMAL_INLINE denormal_filter_double_aggressive(double a)
{
  return ((WDL_DENORMAL_DOUBLE_HW(&a)+0x100000)&0x7ff00000) >= 0x3cA00000 ? a : 0.0;
}
Note that the exponent is increased by 1, so that 0x7FF becomes 0, and we adjusted the cutoff constant for the change.

An extra thought: if you need to pick the cutoff number more precisely, you could change the mask to 0x7fffffff and the cutoff (0x3cA00000) to include some of the fraction digits...

Additional reading: IEEE_754-1985.

Oh and happy bastille day!

3 Comments


Jul 09 2011
$50 of fun

A small r/c car, led lights, and wireless camera.

Comment...


July 01 2011
Music
louie (jam/rehearsal)


June 29 2011
Music
louie (jam/rehearsal)


Jun 27 2011
Spotted last month

Al thought this would make a good picture.

3 Comments


Jun 16 2011
I have this dream

where I'm flying through space
hoping there are no power lines

2 Comments


June 8 2011
incredible industrial design

s/incredible/sleepy/
Yawn:



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June 05 2011
Music
bren (jam/rehearsal)


May 18 2011
Lots of people

I am not at a Pink Floyd concert.

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May 14 2011
A fascinating article from 1987

Reading this piece from the New Yorker about the Mississippi River from 1987 (at schwa's recommendation). I wish it had pictures, but wow.

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May 13 2011
Caffeinated walks ftw



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May 10 2011
Memories from winter

...are now so distant...

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May 10 2011
Another test

I like analog clocks.

1 Comment


May 10 2011
Columbus Park



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April 26 2011
yet another tame impala bootleg



4 Comments


April 22 2011
Music
louie (jam/rehearsal)


April 19 2011
tame impala

I love these guys, I can't wait until next week for their show. Anyway some of their (old?) demos/unreleased tracks have shown up on youtube, and are really wonderful. Such low quality and such good result. Here's a little playlist of some of them I put together:


Also, I would highly recommend their album "Innerspeaker", as well as the EP that has the song "half full glass of wine" on it. Both of those are outstanding.

4 Comments


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