Friday, November 21, 2008

Biggest image I have ever created created

While browsing Wikipedia I found some code to generate nice fractals.

I have adapted the code to create really huge images.

The largest I have to date is computed at 512000 x 300000 pixels. The image is black and white, I use a binary fromat to save space (1 bit/pixel), that still makes the uncompressed file about 20 Gigabytes. Computation time on a Core2Duo 2 Ghz is about 4 days (with some pausing).

I then compute a multiresultion tiff of half size (because it looks better). The final image is about 256000 x 150000.

Here is a detail:

Code I have wrtitten uses OpenMP #pragma. I had the opportunity of trying this code in a new Intel machine that has a total of 16 threads (2 CPUs x 4 Cores x 2 Hyperthreads).  Using a single  parallelfor  instruction allowed me to gain a factor of 10 over single threaded code. Not too bad.  Of course dynamic threads ala Intel TBB would have allowed further gains, but at the expense of more code.


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