TBB Convex Hull Example Input Data Set

I ended my last post with a promise to provide some graphics that would illustrate the type of data that is created as the input for the Threading Building Blocks Convex Hull example problem.

I modified the program to print the data points created by the call to initialize_buf() in main() in the convex_hull_sample.cpp file, then ran my new program, sending the output to a text file.

I then read the 5000000 points using R (the R-Project for statistical computing), and made a simple plot of the data. Here's the plot:

inputPts.gif

As we can see, the density of points at the edges is indeed lower than elsewhere. But, clearly the formula in util::GenerateRNDPoint() creates some artifacts in the data.

Not that this should have any effect on whether or not the code will accurately compute the convex hull solution. I just find it interesting to actually see what's really going into the computations.

I'm still very much at work, studying and working with the convex_hull_sample.cpp code. I'll go further into the code in my next post.

Kevin Farnham
O'Reilly Media
TBB Open Source Community
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