Weblog

A summary of work I've done at the Space Telescope Institute.

Ghosts

I cleaned up the drizzlepac code from the recent testing and checked the changes into github. I added debugging prints to the Lanczos kernel and looked for the discrepancy between the old and new code. There appears to be an off by one error. Possibly the same error is in the gaussian kernel, as the code change is similar. Mark reported a problem with the online STSDAS help script, which is caused by a failure in dbmopen. I have not figured out the reason for the failure yet.

Posted on 31 Oct 2014

Chasing Errors

I spent the day trying to determine the reason for the difference between the old and new code. I added some debugging prints and compared the intermediate results. I blamed the problem on ill conditioning in the formula for the total pixel area, but that did not turn out to be the case.

Posted on 30 Oct 2014

More Debugging

I added the code to drizzlepac to a new github repository. I added some debugging prints to see if I can figure out the reason for the difference in the flux in the new and old versions of drizzlepac.

Posted on 29 Oct 2014

Good. but good enough?

I finished the centroid changes and reported the results. The big surprise was how the flux changes from kernel to kernel.

Posted on 28 Oct 2014

Centroid

I worked on adding a different MOE to the drizzlepac code. It calculates the centroids of objects on the output image and compares them to the reference image. I'm still debugging the change.

Posted on 27 Oct 2014

Still Testing

I finished some tests, ran them, and reported the results. I went back to coding the polynomial interpolator.

Posted on 24 Oct 2014

More Tests

I backed out the polynomial interpolation code and wrote some new tests where the input image is a grid. I've had some successful results, but still need to get some tests to run and write other tests.

Posted on 23 Oct 2014

Not Quite Yet

I wrote the first version of the code to replace linear interpolation with polynomial interpolation in map_value. I did a comparison of the old regression tests to the results from the new code. The results are not quite good enough, so I will have to do more testing.

Posted on 22 Oct 2014

Approximately Right

All the results from the regression tests approximately match the previous results. However, it is an open question whether the match is good enough. Warren suggests using tweakreg as a test and I am waiting on instructions on how to do this. I did another merge from subversion to get the latest version of the code. And I started work on a higher order polynomial interpolation to get possibly more accurate results.

Posted on 21 Oct 2014

More Fixed

I found the other half of the bug I've been hunting for. All the unit tests pass. I ran the regression tests. Some things seem to work ok, but there are some issues I will need to look at more closely.

Posted on 20 Oct 2014