# Presentation: 532685

## Parallel-Processing Astronomical Image Analysis Tools for HST  & SIRTF 

- Kenneth John Mighell
- National Optical Astronomy Observatory

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Outline

- Motivation
- QDPHOT
- QLWPF2
- Development Beowulf Cluster
- Scientific Discovery: Variables in M54
- Performance: Actual, Model, Theory
- Recommendations
- Plans for Year 2

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Motivation

- 	Software tools could prove to be very powerful data mining tools for researchers using the U.S. National Virtual Observatory (NVO).
- 	Quick-look on-demand analysis tools may prove to be very useful to the operations of the NVO.
- 	Successful quick-look analysis tools must be fast and easy to use.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## QDPHOT

- 	My MXTOOLS package for IRAF has a fast stellar photometry task called QDPHOT (Quick & Dirty PHOTometry) which quickly produces good (~5% relative precision) CCD stellar photometry from 2 CCD images of a star field. For example, QDPHOT takes a few seconds to analyze 2 Hubble Space Telescope WFPC2 frames containing thousands of stars in Local Group star clusters.
- 	Instrumental magnitudes produced by QDPHOT are converted to standard colors using the MXTOOLS task WFPC2COLOR.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## QLWFPC2

- 	I have implemented a parallel-processing version of the combination of the QDPHOT and WFPC2COLOR tasks using the MPICH implementation of the Message Passing Interface (MPI) from the Argonne National Laboratory.
- 	This new stand-alone multi-processing WFPC2 stellar photometry task is called QLWFPC2 (Quick Look WFPC2) and is designed to analyze two complete WFPC2 observations of Local Group star clusters in less than 5 seconds on a 5-node Beowulf cluster of Linux-based PCs with a local network based on a Gigabit Ethernet router.
- 	QLWFPC2 is written in ANSI C and uses the CFITSIO library, from HEASARC at NASA’s Goddard Space Flight Center, to read FITS images and the Parameter Interface Library, from the INTEGRAL Science Data Center, for the IRAF parameter-file user interface.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Slide 6

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Slide 7

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Development Beowulf Cluster

- The current implementation of QLWFPC2 was developed and tested on a Beowulf cluster composed of 5 single 1.8-GHz AMD Athalon CPUs with 3 GB total memory connected with a Gigabit Ethernet router with 40 GB of local disk and 120 GB of NFS-mounted disk.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## M54: Globular Cluster in Sgr dSph 

- QLWFPC2 running on 4 processors takes ~2.4 seconds to analyze WFPC2 archive data sets u37ga407r.c0.fits (F555W; 300 s) and u37ga401r.c0.fits (F814W; 300 s) of M54 which is the bright massive globular cluster near the center of the Sagittarius dwarf spheroidal galaxy.  QLWFPC2 analyzed over 50,000 point source candidates and reported V, I, F555W and F814W photometry of 14,611 stars with signal-to-noise ratios of 8 or better.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## M54: Discovery of Variable Stars 

- The analysis of these HST observations of M54 lead to the serendipitous discovery of more than 50 new bright variable stars in the central regions of M54.  Most of the candidate variable stars are found on the PC1 images of the cluster center --- a region where no variables have been reported by previous ground-based studies of variable stars in M54.  This discovery is an example of how QLWFPC2 can be used to quickly explore the time domain of observations in the HST Data Archive.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Actual Performance

- 	Typical QLWFPC2 performance results with two WFPC2 observations of a Local Group globular cluster running on a 5-node Beowulf cluster with 1.8 GHz CPUs and Gigabit Ethernet. The blue points show actual run times for between 1 and 5 processors.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Model

- 	The thin line shows a simple performance model based on measured cluster performance metrics (network bandwidth, disk drive bandwidth, and performance with a single CPU).

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Theoretical Limit

- 	The thick line shows the theoretical limit of performance.  Note the current version of  the QLWFPC2 algorithm already meets the ideal performance values for 1, 2, and 4 processors.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Recommendations

**	****Buy fast machines.**  QLWFPC2 almost met the design goal of 5 seconds with a single CPU.  Note that an infinite number of machines operating at < 1 GHz could not meet the 5-s design goal.
**	****Buy fast networks.** *Gigabit Ethernet is ideally suited for today’s GHz-class CPUs and is now very affordable.* Old networks operating at Fast Ethernet speeds will be bandwidth-bound for tasks requiring large  (>1 MB) messages. The test Beowulf cluster has a latency of 90 microseconds and a sustained bandwidth of 33 MB/s for large messages.
**	****Buy fast disks.** The main disk of the test Beowulf cluster can read large FITS files at a respectable ~30 MB/s with 7200 rpm disks.  Nevertheless, reading 2 WFPC2 images still takes 0.6 s to read which is a significant fraction of the measured total execution times.

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

## Plans for Year 2 

- Develop and implement a multiple-processor version of MATPHOT (MATPHOT-MP)
- Optimize MATPHOT-MP to do *HST*  & *SIRTF* stellar photometry
- Analyze *HST* & *SIRTF*  stellar imaging data
- Test all software with experts & release to general astronomical community at end of 2nd year along with source code & documentation

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28

-    This work is supported by a grant awarded by the Applied Information Systems Research Program (AISRP) of the Office of Space Science of the National Aeronautics and Space Administration (NASA) [Interagency Order No. S-13811-G from NRA 01-OSS-01] .

- AISRP PI meeting 2003         Mellon Institute, Pittsburgh

- 2003 October 28