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Siddharth ManayChandrika Kamath
Center for Applied Scientific Computing
2 March 2005
Progress Report on Data Analysis Work at LLNL: Aug’04 - Feb’05
http://www.llnl.gov/casc/sapphire/
UCRL-PRES-209947-DRAFT This work was performed under the auspices of the U.S. Department of Energy by
University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
Sapphire/SDM AHM/SM 2CASC
Our progress on earlier applications
Feature selection for EHOs (data from DIII-D)— IDL code + instructions transferred to Keith@GAT— visit to GAT + talk— interest in licensing Sapphire software— sample scenario ready for the web
Separation of signals in climate data— a standalone C++ code available which uses our
libraries for PCA/ICA— to be used in illustrating creation of workflows— sample scenario ready for the web
Work done by Erick Cantu-Paz, Imola K. Fodor, Abel Gezahegne, Nu Ai Tang
Sapphire/SDM AHM/SM 3CASC
New application: tracking in NSTX data
Joint work with PPPL (Klasky) Problem: track the plasma over time IDL code implementing a variant of
block matching is too slow Prototyping other block-matching
approaches
National SphericalTorus Experiment
Leveraging LDRD funding (CK); work done by Erick Cantu-Paz, Cyrus Harrison
Sapphire/SDM AHM/SM 4CASC
Joint work with PPPL (Klasky, Pomphrey, Monticello)
Classify each of the nodes: quasiperiodic, islands, separatrix
Connections between the nodes Want accurate and robust
classification, valid when few points in each node
New application: classification of puncture (Poincaré) plots for NCSX
National Compact Stellarator Experiment
Quasiperiodic Islands Separatrix
Sapphire/SDM AHM/SM 6CASC
Polar Coordinates
Transform the (x,y) data to Polar coordinates (r,). Advantages of polar coordinates:
—Radial exaggeration reveals some features that are hard to see otherwise.
—Automatically restricts analysis to radial band with data, ignoring inside and outside.
—Easy to handle rotational invariance.
Sapphire/SDM AHM/SM 7CASC
Piecewise Polynomial Fitting: Dividing data into intervals.
Use the -histograms to find intervals. Need to divide the domain into intervals that are:
—Restricted to regions of that have data.—Small enough so that polynomial will fit the data.—Large enough to span gaps where data is missing
Sapphire/SDM AHM/SM 8CASC
Piecewise Polynomial Fitting: Computing polynomials
In each interval, compute the polynomial coefficients to fit 1 polynomial to the data.
If the error is high, split the data into an upper and lower group. Fit 2 polynomials to the data, one to each group.
Blue: data. Red: polynomials. Black: interval boundaries.
Sapphire/SDM AHM/SM 9CASC
Classification
The number of polynomials needed to fit the data and the number of gaps gives the information needed to classify the node:
Number of polynomials
Gaps one two
ZeroQuasiperiodic
Separatrix
> Zero Islands
2 Polynomials2 Gaps Islands
2 Polynomials0 Gaps Separatrix
Sapphire/SDM AHM/SM 10CASC
Results
3995 points, Separatrix 250 points, 3 Islands
Puncture 1, node 79
Zoom around =1.6 Zoom around =1.6
Sapphire/SDM AHM/SM 17CASC
Future work
Set up web pages for climate and fusion scenarios NSTX data: continue building and testing block-
matching algorithms NCSX data
— continue interactions with Neil, Don, Scott — continue to refine and validate approach— investigate ways of making it more robust— investigate exploiting nearby nodes— design and implement in C++ for insertion into
PPPL analysis pipeline