Spelling Toy iPhone App Released February 9th, 2010
Patrick Stein

I am pleased to announce, that my Spelling Toy for Kids is now available on the iTunes Store.

The first five respondents to this article will receive a Promotional Code to download the app for free! (Edit: all promo codes dished out… if you really want one and will publicly review my app in your blog, I’ll dig up another promo code for you.)

Features

  • Kid-friendly interface! Just pick the letters you want!
  • Guides your child to the proper spelling of each word.
  • Adapts to your child! Cards that consistently give your child trouble show up more often.
  • Support for English, Spanish, and French! (German and Japanese Kana coming soon)
  • Lots of words to learn (with more coming soon).
  • Three different skill levels to challenge your kid!
  • Exercise some or all of the categories: Numbers, Colors, Foods (with more coming soon).

Lisp Fourier Transform Library Faster Yet (v1.3) October 13th, 2009
Patrick Stein

I released version 1.3 of my Common Lisp Fourier Transform library today. It is significantly faster than yesterday’s version. On my MacBook Pro in SBCL 1.0.30 with a 512 by 512 by 16 array, version 1.3 takes 3.74 seconds where version 1.2 took 9.77 seconds and version 1.0 took 25.31 seconds. For a breakdown of performance on various array sizes with various Lisp implementations, see the performance section of the library page.

Most of the speed improvement in this version came from memory improvements. Version 1.3 doesn’t cons at all in SBCL during the processing of each row. Version 1.2 inadvertently consed three rows worth of complex numbers for every row transformed.

My library is still about 25% slower than Bordeaux FFT for one-dimensional arrays. My library, however, has full support for multi-dimensional arrays where Bordeaux-FFT does not.

I also included some validation test cases using NST to this release. To try them, go to the library directory, hop in your Lisp, and load regression.lisp.

Lisp Fourier Transform Library Faster October 12th, 2009
Patrick Stein

I released version 1.2 of my Common Lisp Fourier Transform library today. It is significantly faster than the old version. On my MacBook Pro in SBCL 1.0.30 with a 512 by 512 by 16 array, version 1.2 takes 9.77 seconds where version 1.0 took 25.31 seconds. Version 1.2 consed 2.4M while version 1.0 consed 7.4M. Neither version should have to cons nearly that much, so there’s still work to be done.

This release is significantly faster under Clozure64 1.3-r11936, too. For a 512 by 512 array, version 1.2 takes 2.72 seconds (single-threaded) and 2.07 seconds (multi-threaded) where version 1.0 took 4.45 seconds (single-threaded) and 3.06 seconds (multi-threaded).

My library is still about 1/2 to 1/3 the speed of Bordeaux FFT and still allocates memory in situations that Bordeaux does not. Hopefully, I can close those gaps most of the way soon.

Public Domain Fourier Transform Library for Common Lisp October 7th, 2009
Patrick Stein

In response to my recent post about genetically selecting cosine waves for image approximation, several reddit commentors said that I should just have taken the Fourier transform, kept the largest 100 coefficients and did the inverse Fourier transform. [I haven’t run the RMS calculation on the result yet, but visually, it looks pretty nice with my test image. More details on that in a later post.]

The Lisp code that I used in that article didn’t actually use Fast Fourier Transforms. To test the commentors’ claims, I needed an FFT library in Lisp. I searched around a bit and found an FFI (Foreign Function Interface) wrapper around the FFTW library. After fiddling with that library and the wrapper for about two hours, I bailed on it and wrote my own Fast Fourier Transform library entirely in Lisp.

More information as well as links to getting the code are here: nklein / Software / CL-FFT.

geoma v1.2.2007.08.20 August 20th, 2007
Patrick Stein

This version simply contains some tweaks to deal with more modern C++ compilers.

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