As of Sun Jun 23 8:03:27 2024

DDT: Verification/timing test; see Y2K for current test


TCODE                              INIT,TEST,READ, or WRIT
TMODE                              T or M; Test or Master input
TMASK           1.0       127.0    test selection bit mask
DDTSIZE                            SMALL,MEDIUM,LARGE,HUGE test
DDISK           1.0        35.0    Disk drive #: master UVDATA
MDISK           1.0        35.0    Disk drive #: other masters
TDISK           1.0        35.0    Disk drive #: test images
IOTAPE          0.0         9.0    Input/Output tape drive #.
DDTDISK                            Disk area for READ and WRIT
EDGSKP          0.0        64.0    Pixels to skip at edges
TERSE          -1.0        99.0    > 0 => reduced output
                                   Printer disk file to save
BADDISK                            Disks to avoid


Use:  DDT performed the AIPS verification test of an AIPS system.
      See RUN files DDTLOAD.001 and DDTEXEC.001.  The purpose of
      the inputs file is to perform bounds checks on the
      parameters and to enable the use of TPUT and TGET.


 TCODE    String*4      'INIT', 'TEST', 'READ', or 'WRIT'
 TMODE    String*1      'T' or 'M'; Test output from previous
                        task as input to current.  'M' requests
                        master input to all tasks.
 TMASK    Scalar        test selection bit mask (1-127)
 DDTSIZE  String*8      'SMALL', 'MEDIUM', 'LARGE' test
 DDISK    Scalar        Disk drive # (1-9) master UVDATA
 MDISK    Scalar        Disk drive # (1-9) other master files
 TDISK    Scalar        Disk drive # (1-9) test files
 IOTAPE   Scalar        Input AND output tape drive #. (1-9)
 DDTDISK  String*8      Logical name of disk area to be used for
                        FITS-disk files in READ or WRIT instead
                        of actual magnetic tape.
                        ' ' => use magnetic tape.
 EDGSKP   Scalar        Number of pixels to skip at edges in
                        comparing test and master images
 TERSE    Scalar        > 0 => reduced output:
                          > 0 = drops INPUTS for all tasks and
                                TPHEAD when reading tape
                          > 2 = also drops CATALOG listings
                          > 3 = also drops IMHEADER listings
                        Use -1 on all new or uncertain systems,
                        or when determining the AIPSMark(93).
 OUTPRINT String*48     Disk file name in which to save the line
                        printer output.   ' ' => use scratch and
                        print immediately for interactive jobs -
                        batch jobs use OUTPRINT =
                        'PRTFIL:BATCHjjj.nnn' (jjj = job #, nnn
                        = user #).  When OUTPRINT is not blank,
                        multiple outputs are concatenated and
                        the file is not actually printed.
 BADDISK  Array         Any bad disks to avoid for scratch files
                        (also private dirs; use | to separate)

DDT runs in four different modes: (TCODE)
   INIT = starts from the original master UV dataset, and
           (re)computes master files (does ALLDEST).
           The "mask" TMASK controls which steps execute.
   TEST = re-does the INIT computation but stores the new
           files under different names and compares against
           masters. The "mask" TMASK controls which steps
           execute. TEST steps use either the TEST run output
           of the previous step (TMODE=T) or the INIT run
           output (TMODE=M).
   WRIT = write master or test files to tape (TMODE matters)
   READ = read master files from tape.

A binary mask controls which steps of the test execute:
   TMASK +1=>SORT,  +2=>UVMAP, +4=>APCLN,
         +8=>CALIB, +16=>MXmap,  +32=>MXclean,
   For example, TMASK=54 would execute UVMAP,APCLN,MXmap,and

Input data files for test steps are selected by the TMODE
   adverb which has two possible values: 'T' for those made
   in previous steps of the present test or 'M' for the
   master "correct" data sets input from tape.

The adverb DDTSIZE controls the size of the test performed:
   'S'    256x256 image, 2000 clean components, 8000 vis
   'M'    512x512 image, 5000 clean components, 15000 vis
   'L'    1024x1024 image, 15000 clean components, 75000 vis


Explanation of DDT:               (DCW, Feb/Mar85, EWG Nov85,
                                   CF Mar89, GL Jan90, PM Sep94)

DDT exercises the "Dirty Dozen" of AIPS tasks using data for one
of three sources.  The three data sets provide three sizes of
"real" AIPS reduction: 256x256 images with 8000 vis. and 2000
components, 512x512 with 13000 vis. and 5000 components, and
1024x1024 with 77000 vis. and 15000 components.  The sources for
the "small" and "medium" problems were originally background
sources for an HI absorption experiment by Liszt and Greisen
while the "large" problem uses data supplied by Alan Bridle.

The DDT problem is intended to be used to certify the correct
execution of all AIPS systems. (The smallest is small enough to
run in less than one day on all machines which will ever run
AIPS.)  Its execution time is significant and easily measurable
on modest systems such as the Sparc IPX, and approximate timings
can also be obtained for faster systems.  The AIPSmark(93) is
based on the total elapsed time for the Large DDT suite; see
AIPS memo 85 for full details.
Steps to execute the DDT Test on a new computer:

1. Log in to AIPS under the user number which will own the data
   files and the SAVE/GET files associated with the test.  It is
   probably convenient to clear your AIPS message file before
   proceeding: PRNUM=-1; (PRTMSG possibly) ; CLRMSG

2. Now do the POPS command "RUN DDTLOAD". This initiates the
   compilation process, which on most modern systems will not
   take more than a few minutes.  You may want to execute the
   POPS command "PRTMSG" afterwards to document the compilation
   of the test procedures.

3. The next step is to read the data files from the tape, or
   from disk.  On tape, these are files 1 - 11 for the small
   problem, files 12 - 22 for the medium problem, and files 23 -
   33 for the large problem.  Alternately, if you have the files
   on disk, merely set the DDTDISK adverb to point at where the
   files reside (you need to define or use a "logical" or
   environment variable with an uppercase name before starting
   AIPS to use this feature; e.g. FITS).  The DDT files are
   available via anonymous ftp to in
              cd pub/software/aips/FITS/31DEC04
              MGET DDTL*                  (or DDTS*, DDTM*)

   On tapes, the first one in each set of 11 is the original
   visibility data set of the DDT problem.  Subsequent files are
   the "master" versions of files computed from the original
   dataset.  The read process consists of the following steps:

      Also specify BADDISK as needed
      DDTSIZE='SMALL' or 'MEDIUM' or 'LARGE'  (desired problem)
      TCODE='READ'; TPUT DDT         (TPUT saves adverb values)
      MOUNT the tape unless you have the disk files
      DISMOUNT the tape or remove/backup the disk files
      PRTMSG                       (documents data read process)

   In the case of a DDT tape, the READ mode will rewind the tape
   and skip over the data for the smaller problems (if 'SMALL'
   wasn't given).  It will then execute FITLD to read the UV and
   image files to disk.  At the end of the process, it rewinds
   the tape and prints a directory of the disk files.

   NOTE: DDTEXEC will insist on having non-default values for

4. Now it is time to actually perform the test.  The 'TEST' mode
   recomputes the various files.  All map results are compared
   to the master versions which were read from tape in the
   previous step.  There are two ways to perform the
   calculations: with each step computed from the result of the
   previous test calculation in the sequence, or else from the
   result of the previous MASTER computation in the sequence.
   The first mode (TMODE='T') tests how well the system under
   test is able to reproduce a complex sequence of calculations
   beginning from a designated starting point.  That is, it
   measures the accumulation of error in the system.  The second
   mode (TMODE='M') tests the steps of the sequence separately
   so that errors created in each step can be isolated.  It also
   should use tape.  It is also the step used for calculating
   the AIPSmark(93).  Both tests are important, and both should
   be performed to certify fully the scientific adequacy of an
   AIPS installation, but it is generally best to use TMODE='M'
   as the initial (and primary) test of all systems.  The steps

      CLRMSG                       (prepare for test results)
      TGET DDT
      TCODE='TEST'; TMODE='M'; TMASK=127
      DDTSIZE='SMALL' or 'MEDIUM' or 'LARGE'  (desired problem)
      EDGSKP=4, 8, or 16 for small, medium or large DDTSIZE
      TPUT DDT                     (saves the adverb values)
      PRTMSG                       (print out the test results)

   For the AIPSmark(93) benchmark, TERSE should be set to -1.
   The message file from DDTEXEC will be more than 2000 lines
   long.  It is intended to be the major item documenting the
   test procedures and results.

   Making a second run with TMODE='T' is not required, but is
   generally advisable to evaluate the accumulation of error.
   This process also checks the manipulations of visibilities,
   antenna files, and gain files; these processes are not really
   tested in the 'M' mode because AIPS currently has no
   comparison operators for files of these types. The 'T' mode
   tests them by their effect on subsequent map results.  This
   is particularly important for the output of the
   self-calibration program CALIB.

   One can also rerun the tests with a different value for the
   VERSION adverb.  One can also use this option to test
   experimental versions of specific tasks.

5. The 'WRIT' mode tests task FITTP, while 'READ' tests FITLD.
   The basic idea is to produce a tape (or FITS disk files), and
   then to read that tape or those files on an AIPS system to
   verify that it yields correct results.  It follows that
   generating a new tape with the 'WRIT' mode and then executing
   'READ' and 'TEST' on it will also effectively test the tape
   tasks.  Better yet, take the tape to another AIPS and run DDT
   on it!  This verifies the intercommunication of the systems.
   Obviously, use of FITS disk files will do little to test your
   tape I/O.

   Note that DDT assumes that the tape consists of the 11 SMALL
   data files, followed by 11 MEDIUM data files, followed by 11
   LARGE data files.  You should first run DDT in WRIT mode for
   the SMALL problem.  If generating a tape, having done this,
   you may then (optionally) run DDT in WRIT mode for the
   medium problem and, having done all this, you may then WRIT
   the LARGE problem.

   The steps are:

      TGET DDT
      DDTSIZE='SMALL' or 'MEDIUM' or 'LARGE'  (desired problem)
      TPUT DDT
      PRTMSG                       (print out the test results)

   Note that when we say "tape", we mean either magnetic tape in
   the usual sense, or pseudo-tape disk files.  The latter are
   selected by setting DDTDISK to a non-blank value which is the
   logical name (environmental variable) for the disk area to be
   used.  The disk files are given a fixed and obvious pattern
   of names (DDTsnnnnnn, where s is S, M, L, or H and nnnnnn is
   the image name related to the task name).

6. Finally, one wants to know the accounting statistics from the
   test runs.  The accounting listing can be correlated with the
   message file listings in order to analyze the performance of
   the tested system.  DDT now runs task PRTAC to produce the
   desired information.  Note that PRTAC has exclusive access to
   the accounting file until it finishes, and so various tasks
   may complain while they are waiting to get access to the

   The listing produced by PRTAC will have one line for each
   execution of any task or program AIPS.  The columns of the
   listing give the taskname, POPS#, user#, start-time, real-
   time, CPU-time, and "IOCNT".  Asterisks mark any run that
   aborted.  After this basic sequential listing comes a listing
   by task name giving the totals accumulated by each task.  The
   listing is given in two sort orders.

Regarding "cloning":

It is obvious that DDTLOAD and DDTEXEC are cloneable.  First, a
clone of DDT could process another dataset; this would be done
by adding additional allowed string values for DDTSIZE and
renaming the input UV data set DDDT?, where ? is the first
character in the new allowed string value.  The adverb values
needed for the new data set, are initialized in the DDTPROC
procedure which is SAVEd in DDTSAVE.  Second, the general
pattern of executing and testing the tasks in succession will
work for a wide variety of AIPS tasks and data types.

                Interpretation of Test Results

The results of the mapping tests are recorded as the number of
BITS of accuracy.  The BITS of accuracy are defined in two ways,
by the MAX difference in the Master image and the Test image and
by the RMS differences in the images.  The BITS measured by the
the base 2 logarithm of the ratio of PEAK and DIFFERENCE of the

The BITS are calculated as -3.3219 * LOG(DIFF/PEAK).  (LOG is
the Base 10 Logarithm; 1/LOG(2) = 3.3219)

The expected BITS of accuracy for the tasks are in the range of
10 to 20 BITS.  The RMS BITS of accuracy is always greater than
the PEAK BITS of accuracy.

For further information on the interpretation of the results,
refer to AIPS memo 85 and other memos in the AIPS memo series
that relate to the DDT tests.  These are available via anonymous
ftp and the world wide web on the internet; ftp to,
cd to /pub/aips/TEXT/PUBL/ .  The web page is .