[daip] draft Visiting Committee report

[Eric Greisen]

          March 2006 Visiting Committee Report on AIPS

The 31DEC05 version of AIPS was developed through 2005 and then frozen
in late December.  It was available for download (and update via the
"midnight job" or MNJ) during development and the frozen version may
now be downloaded.  The new test version, 31DEC06, was started in
December 2005 and is available for download and update.  We have
developed tools to count downloads of full AIPS versions and to count
access to the main "cvs" site.  The latter reflects both initial
installation and updating of the development version; frozen versions
do not generate cvs accesses.  Counting each unique IP address as a
"site", there were cvs contacts from 982 sites in 2005 of which 252
appear to have run the MNJ at least occasionally.  The frozen 31DEC04
version was downloaded by 246 sites and the 31DEC05 version, while
under development, was downloaded by 832 sites.  A total of 1460
unique IP addresses downloaded a copy of AIPS and/or accessed the cvs
site.  At this writing (21 February), the frozen 31DEC05 version has
been downloaded by 76 sites and the development 31DEC06 version has
been downloaded by 214 sites.  The total number of IP addresses is
already 425.

We have found that the Fortran compiler developed by IBM for MacIntosh
systems generates code that is 50% faster than that produced by the
GNU compilers.  On Pentium IV machines, the code generated by the
Intel compiler is 30% faster than that generated by the GNU compilers.
In fact, The Intel-compiler binaries are also about 7% faster on
non-Intel machines (AMD 64s).  A similar speed up is seen with the SUN
compiler on Solaris machines.  Unfortunately, these compilers are
moderately expensive. Therefore, we have made available binary
distributions of AIPS.  This binary form is available both for the
frozen 31DEC05 release and the development 31DEC06 version, including
periodic updates (daily are possible) via the MNJ.  So far in 2006, 90
sites have accessed the binary version of 31DEC06 and 46 sites have
accessed the binary version of 31DEC05.

Models for the primary flux calibration sources are now provided with
AIPS.  There are four sources, 3C48, 3C138, 3C147, and 3C286, at the
three highest VLA frequency bands, K, Q, and U.  These models were
provided by Claire Chandler.  Lower frequency models at X, C, and L
bands for 3C48 and 3C286 have been provided so far by Amy
Mioduszewski.  We expect, in the long run, to provide models for 
all four sources at all VLA frequencies.  The pipeline procedures for
the VLA are being revised to use these models.

Steps are being taken to support greater use of pipeline and other
procedures in AIPS.  The new experimental task FLAGR uses the internal
statistics in a data set to flag that data set.  It was corrected to
flag times at which it fails to find antenna-based amplitudes, phases,
and weights from the baseline data.  With this correction, it appears
that the task is quite effective in flagging calibration sources and
it is being incorporated into new pipeline procedures.

The VLBA correlator requires an estimate of the Earth Orientation
Parameters in order to correlate an observing session.  Unfortunately,
the final best estimates of these parameters are usually not available
at correlation time.  For a period of time, the VLBA correlator used
very preliminary estimates rather than better estimates which were
available by correlation time.  AIPS task CLCOR was given a new option
to read the final best EOP estimates and correct the data to those
from the EOP values used at correlation.  An AIPS procedure was
written which fetches these estimates from the web and then runs this 
CLCOR option.

Because of a shortage of disk playback units at the VLBA correlator
and limitations in the instantaneous bandwidths which may be
correlated, the old AIPS tasks VBMRG and VBGLU are again needed.  They
have had various bugs and limitations corrected and VBGLU is about to
be rewritten so that no data are lost in the process.

AIPS uses dynamic memory to allow for large-memory problems without
burdening normal uses of quite a number of tasks.  The code was
revised to support those 64-bit addressing computers which allocate
dynamic memory at virtual addresses well removed from the virtual
addresses assigned to the pre-compiled code.  AMD-64 computers under
Linux are among this class and NRAO has acquired one to support this
architecture in aips++ (and AIPS).

Miscellaneous enhancements including generalizing all tasks which
handle box files so that they support all box and field definitions
used by IMAGR.  The new task CCRES allows the addition or subtraction
of Clean component models in images without requiring power of 2
images and point sources exactly on image cells.  The remaining
Tektronix emulation tasks, including XGAUS and XBASL, were revised to
offer more reliable TV-based methods.  A spectral-index fitting task
was written and other tasks revised in anticipation of problems with
spectral index over the very wide EVLA bandwidths.  A spectral-index
correction method is being added to IMAGR.

Full information on AIPS may be found beginning at the main web page
     http://www.aoc.nrao.edu/aips/