[CIG-SHORT] PyLith 1.8.0 released

[Brad Aagaard]

Greetings,

I am pleased to announce the release of PyLith 1.8.0, a finite-element
code designed to solve dynamic elastic problems and quasi-static
viscoelastic problems in tectonic deformation.

This release adds estimating the stable time step for explicit time
stepping, adds a post-processing utility for computing the moment
magnitude and average slip for any fault output snapshot, includes a
couple of additional examples of CUBIT meshing techniques, fixes
several bugs in PyLith v1.7.1 and corrects some typos in the
manual. We strongly recommend all users of previous PyLith releases
switch to this latest release.

You can download the source code and binaries from

     http://geodynamics.org/cig/software/packages/short/pylith

Detailed installation instructions for the binary packages are in the
User Manual with detailed building instructions for a few platforms in
the INSTALL file bundled with the PyLith Installer utility.


RELEASE NOTES - PyLith v1.8.0

****************************************************************
See the README file for changes required to switch to the v1.8.0 release 
series from previous versions.
****************************************************************

* New features

   * Additional flexibility in PETSc nonlinear solver parameters

     The default line search type for the PETSc nonlinear (SNES) solver
     is a customized backtrace method included in PyLith. The user may
     now select alternative line search types (basic, bt, l2, cp)
     available in PETSc.

   * Post-processing utility pylith_eqinfo to compute slip information.

     This post-processing utility computes the moment magnitude,
     seismic moment, seismic potency, and average slip at
     user-specified snapshots in time from PyLith HDF5 output.
     Information is given for each fault and across all faults. See
     the Post-processing section of the manual in the Running PyLith
     chapter for more information.

   * Computation of the stable time step for explicit time-stepping.

     The stable time step for explicit time-stepping is computed based
     on the CFL condition and minimum edge lengths. For triangular and
     tetrahedral cells we also account for a reduction in the stable
     time step due to distorted cells (e.g., slivers and needles). See
     the Stable time step section in the Materials chapter of the
     manual for more information.

   * Output the stable time step for each cell in a material.

     Output cell_info_fields "stable_dt_implicit" and
     "stable_dt_explicit" can be included in material output.

   * Added netCDF Python module to binary distribution to provide
     Python interface to NetCDF files, including Exodus-II files. This
     is used in a new meshing example for setting the discretization
     size using an Exodus-II vertex field. Note that this required
     updating the NetCDF library.

   * New CUBIT meshing examples demonstrating how to merge surfaces and
     use and an Exodus-II vertex field to specify the discretization
     size.
     + examples/meshing/surface_nurbs/merge_surfs
     + examples/meshing/cubit_cellsize


* Bug fixes

   - Fixed omission of synchronization of stable time step computation
     among processors. Minimum time step among all processors rather
     than local value should be used.

   - Fixed density scale not being set in NondimElasticQuasistatic.
     Density scale should be set based on shear modulus, length scale,
     and relaxation time.

   - Added warning when initial state for a fault constitutive model is
     not set. If an initial state value is not given, for rate-state
     friction using a default value of L / reference slip rate. Other
     fault constitutive models use a default value of 0.0 for initial
     state variables.

   - Separated tensor components in Xdmf files to avoid confusion. The
     corresponding HDF5 files remain unchanged.

   - Removed explicit time-stepping formulation with non-lumped
     Jacobian. This formulation was not setup properly for spontaneous
     rupture models and is too computationally expensive for practical
     problems. The ExplicitLumped* formulations are now simply Explicit*.

   - Fixed parallel bug that resulting in inconsistent orientation of
     fault slip directions. Flipping the fault orientation was not
     synchronized across processors. This bug would only appear when
     running in parallel with faults that change from dipping in one
     direction to dipping in the opposite direction.

   - Fixed bug in setting name of field in OutputSolnPoints when output
     multiple fields. This bug caused the name of the first output
     field to be used and output data to overwrite each other.