AIPS quarterly report (Q1), Mar 22 1999 --------------------------------------- Versions -------- The current TST version of AIPS (15APR99) is distributed nightly to 27 sites throughout the US, Europe and Japan. Full support for SVLBI processing has been available since 15APR98. The 15OCT98 version of AIPS has been distributed to over 243 sites, running Solaris, Linux, DEC Alpha, HP and SGI versions. The overall number of AIPS installations has grown over the last two years; 15APR98 and 15OCT98 are amongst the most widely-distributed versions ever. The majority (70%) of AIPS distributions are now received by ftp, although the CD-ROM distribution is growing rapidly in demand. One attractive feature of the CD ROM is the ability to use the binaries directly from the CD, keeping only data and a small footprint (10MB) on the processing machine. This is particularly attractive for laptop computers. Personnel --------- There are ~4 full-time equivalent employees in the AIPS group. Early in 1999 Tony Beasley transferred full-time to CV. Documentation ------------- The AIPS Cookbook has been converted from Tex to Latex as the first stage in placing the cookbook on-line. All help documentation is now available through a browser (using the command XHELP inside AIPS), with complete cross-referencing. Hardware -------- AIPS running on Linux PCs continue to show impressive absolute and cost-relative performance, the best PC AIPSMARK so far is 16.1. A new benchmarking suite will need to be produced within a year or two to more adequately measure the performance (current suite now completes in under 5 minutes, which may be too short to be representative). Using the g77 EGCS 1.0.3 compiler the AIPS group have now produced a native port of AIPS to Linux running on a DEC Alpha; AXLINUX has now been added to the list of supported architectures. Further Y2K testing of AIPS was performed by using the VLBA correlator to produce a dataset seemingly observed in February 2001. Loading the correlated data into AIPS did expose small deficiencies in date reading in tables which have been addressed. We believe AIPS is Y2K compliant. A stand-alone workstation with AIPS installed was clocked through January 01 2000 with no apparent AIPS problems. Real-time filling of VLA data to Linux machines was enabled in early 1999. General Issues -------------- - Consolidation and version numbering of the tasks involved in porting VLBA correlator data to the USNO/GSFC Calc/Solve package has been completed. - CONFI - A task CONFI was added to find optimal configuration of an array using the criteria of minimizing side lobes. This task has been written for MMA studies but can be used for general array design. - Image sizes throughout AIPS are now fully parameterized; the system can now deal with images of 16384 pixels on a side. - The new task UVCON will generate a u-v database for an interferometric array whose configuration is specified by the user. Visibilities corresponding to a specified model, and Gaussian noise appropriate for the specified antenna characteristics are calculated for each visibility. The array geometry can be specified in three different coordinate systems: equatorial, local horizon, and geodetic. There is an option of using set of different frequencies to improve UV coverage. - A new verb TAPES was added, allowing a user to see what tape drives are attached to their system at any time (only shown at startup at present). The remote tape system can now interrogate remote tape drives as to their status (i.e. available or not). - FITAB is a new AIPS task intended to replace FITTP (gradually). It has a number of advantages to FITTP and would replace it directly except that its output cannot be read by older versions of AIPS and by other software systems which do read AIPS random-groups uv-data format. The advantages of FITAB are: (1) For images, FITAB allows the specification of the value of the least bit, allowing more compression if the least bit is controlled to have a value related to the image rms (e.g., rms/4). FITTP uses the full range of integer and floating output values and is, therefore, not particularly compressible. (2) For UV data, FITAB writes out the data in a binary-tables form rather than in a random-groups form. This has the advantage that the data may be written in "compressed" format identical to that used on disk inside AIPS. FITS files that take advantage of this option can be as much as three times smaller than those written by FITTP. (3) For UV data, FITAB is able to break up the output into multiple files, each containing a "piece" of the AIPS file. Each of these files contain the full contents of many of the descriptive files (source, flag, index, antenna) as well as the corresponding time range for any calibration files (CL, SN, IM, TY, etc.). These tables appear in the files before the uv data. Each piece of an AIPS data set can be read and used individually or together with some or all of the other pieces. FITAB is currently being tested within NRAO. Bugs ---- - A bug involving INTEGER*2 arithmetic in a number of subroutines when compiled with the Linux EGCS g77 compiler (Version 1.1 and above) was found. This bug silently corrupts data when writing out FITS files using Linux. These routines have been modified in 15APR99 and the EGCS people informed. - A serious bug affecting the w-term correction of visibilities when imaging fields distant from the phase center was fixed. This bug occurred if the first channel of a u-v dataset being imaged was not at the reference frequency of the file. Note, this bug was introduced sometime before 1990. - A bug in the Linux glibc library concerning the interaction between AIPS sockets and the YP network services was identified and addressed. The bug has been brought to the attention of the Linux community.