    NOTES ON THE VERSION OF 1999-12-06

    This is a fairly minor release, with a few bug fixes, a couple of
    which might be important, some new experimental facilities that aren't
    of general interest (at least not yet), and a few added conveniences
    and other minor updates.

    Changes in this version:

    1) Several new ways of computing trajectories have been implemented,
       in addition to the old leapfrog method.  See mc-spec.doc for details.
       The new methods may be better for some applications, but they aren't
       uniformly better than the leapfrog method, and they are not recommended
       for general use.

    2) New "spiral" and "double-spiral" operations were added.  See
       mc-spec.doc for details.  These are experimental.  Quantities
       m0, m1, m2, m3, m4, and m5 were added to support this feature.
       See mc-quantities.doc for details.

    3) The mc-spec program now lets you see all the specifications in
       the log file, at any iteration, with "mc-spec log-file all".  See
       mc-spec.doc for details.

    4) New "multiply-momentum" and "set-momentum" operations were added, for
       testing and research purposes.  See mc-spec.doc for details.  These
       are probably of no interest to most users.

    5) An install-arch shell file for conveniently maintaining separate
       versions of the compiled programs for different machine architectures
       has been added.

    6) The documentation has been updated and corrected in various fairly
       minor ways.

    7) Compute times quoted for the demos are now for a Linux system with
       a 550MHz Pentium III processor.

    Bug fixes.

    1) A bug was fixed that caused derivatives to sometimes be calculated
       incorrectly when the "omit" option was used with Gaussian process
       models.  The effect was to increase the rejection rate for "hybrid"
       operations, but the final answer (if convergence was reached) would
       still be correct.

    2) A bug was fixed that caused the "first:last" option of the met-1
       operation to be ignored.

    3) A bug was fixed that sometime caused data-spec to report spurious
       errors when targets were log-transformed.

    4) A bug was fixed that caused problems with automatic scaling of target
       variables when they were all the same (ie, had standard deviation of 0).

    5) The xxx-stepsizes and xxx-grad-test programs were changed to not try
       to open the log file for writing (which might not be allowed), seeing
       as they only need to read it.

    Known bugs and other deficiencies.

    1) The facility for plotting quantities using "plot" operations in xxx-mc
       doesn't always work for the first run of xxx-mc (before any
       iterations exist in the log file).  A work-around is to do a run of
       xxx-mc to produce just one iteration before attempting a run of
       xxx-mc that does any "plot" operations.

    2) The CPU time features (eg, the "k" quantity) will not work correctly
       if a single iteration takes more than about 71 minutes.

    3) The latent value update operations for Gaussian processes may recompute
       the inverse covariance matrix even when an up-to-date version was
       computed for the previous Monte Carlo operation.

    4) Covariance matrices are stored in full, even though they are symmetric,
       which sometimes costs a factor of two in memory usage.

    5) The "p" option of net-pred isn't allowed for survival models with
       piecewise-constant hazard.  There's no big reason for this - I just
       haven't gotten around to it.