[CIG-SHORT] PyLith 1.6.0 is now available

[Brad Aagaard]

Greetings,

I am pleased to announce the release of PyLith 1.6.0, a finite-element
code designed to solve dynamic elastic problems and quasi-static
viscoelastic problems in tectonic deformation.

This release adds several new features to PyLith, including (1)
parallel binary output via HDF5 files, (2) a 2-D generalized Maxwell
viscoelastic bulk constitutive model, (3) a time-weakening fault
constitutive model, (4) global uniform parallel mesh refinement, (5) a
custom algebraic multigrid preconditioner to improve the efficiency of
the solver for quasi-static problems, and (6) a new installation
utility for building from source.

We strongly recommend all users of previous PyLith releases switch
to this latest release. In addition to adding features this release
also fixes a number of bugs related to fault friction and initial
strains for viscoelastic models. We have added a few more consistency
checks and optimized some data structures. Parameter files used with 
v1.5 are fully compatible with this release (no changes are necessary).

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

* New features

   * Parallel binary output via HDF5

     Provides much faster output by writing HDF5 files in parallel,
     which can be accessed directly from Matlab or indirectly from
     ParaView or Visit via automatically created Xdmf files. Temporal
     data is stored in 3-D arrays, permitting slicing in time and/or
     space. See examples/3d/hex8 Steps 6-9 and examples/2d/subduction
     in the tutorials for examples.

  * 2-D generalized Maxwell viscoelastic bulk rheology

     Added a 2-D generalized Maxwell viscoelastic bulk rheology
     corresponding to the plane strain version of the 3-D generalized
     Maxwell viscoelastic model.

  * Time-weakening fault constitutive model

     Added a linear time-weakening fault constitutive model. Some
     spontaneous rupture modelers prefer this model over linear
     slip-weakening because it is easier to maintain resolution of the
     cohesive zone.

  * Global uniform parallel mesh refinement

     Permits running larger problems through uniform global refinement
     of the mesh by a factor of two (reduces the node spacing by a factor
     of 2) after the mesh is distributed among processors. This allows
     running problems that are 4x larger in 2-D and 8x larger in
     3-D. See examples/3d/tet4 Steps 2 and 4 for examples.

  * Custom algebraic multigrid preconditioner

     Adds a custom preconditioner for Lagrange multiplier degrees of
     freedom associated with fault slip via prescribed slip or
     spontaneous ruptures with algebraic multigrid preconditioning for
     quasi-static solutions. In most cases, this results in fewer
     iterations in the linear solve and the number of iterations
     increases much less with problem size. See examples/3d/tet4 Steps
     2 and 4 for examples.

   * PyLith installer utility

     This utility provides a much more robust method for building
     PyLith and all of its dependencies from source, including
     dependency checking, installation to a central location, and
     creation of a shell script to set environment variables.

* Bug fixes

     - Fixed the fault friction implementation to correctly update
       Lagrange multiplier values when the slip is overestimated in an
       iteration. This primary fixes problems encountered with the use
       of the Dieterich-Ruina rate and state fault constitutive model.

     - Corrected viscoelastic rheologies to properly account for a
       nonzero initial strain tensor.