[CIG-SHORT] New PyLith release - version 1.5.0

[Brad Aagaard]

Greetings,

I am pleased to announce the release of PyLith 1.5.0, 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) fault
friction with a few widely-used fault constitutive models, (2) an
optimized solver for explicit time-stepping with a lumped Jacobian
matrix, (3) a total Langrangian formulation for rigid-body motion and
small strains, (4) use of scientific notation in VTK output files with
user-specified precision, and (5) use of nodeset names in CUBIT Exodus
files. We encourage all users of previous PyLith releases to switch to
this latest release.

We strongly recommend all users of previous PyLith releases to switch
to this latest release. In addition to adding features this release
also fixes a number of bugs (see top-level README file). Also see the
README file for changes required to switch to the v1.5.x release
series from previous versions.

You can download the source code and binaries from

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

Detailed installation instructions are in the User Manual with example
installation procedures for a few platforms in the bundled doc/install
directory.


RELEASE NOTES

   * Fault constitutive models

     Added fault friction interface conditions with static
     friction, linear slip-weakening friction, and rate- and
     state-friction with the ageing law. The implementation can be used
     in static, quasi-static, and dynamic problems.

   * Drucker-Prager elastoplastic bulk rheology

     Added a Drucker-Prager elastoplastic bulk rheology. This is a
     perfect plasticity implementation (no hardening). This is a
     nonlinear constitutive model, so the nonlinear solver is required
     when this rheology is used. Refer to the 'Material Models' section
     of the manual.

  * Plane strain Maxwell viscoelastic bulk rheology

     Linear Maxwell viscoelastic rheology for plane strain problems.

   * Finite-deformation formulation

     Added a finite-deformation (rigid body motion and small strains)
     implementation of elasticity with stress calculated using the
     Second Piola-Kirchhoff stress tensor and strains calculated using
     the Green-Lagrange strain tensor.

   * Lumped Jacobian for explicit-time stepping

     Added the option to lump cell Jacobian matrices to form a diagonal
     system Jacobian matrix for explicit time stepping. This decouples
     all degrees of freedom and permits use of a fast, trivial, direct
     solver.

   * Optimized elasticity objects

     Added optimized elasticity objects for the most popular cell types
     and basis functions (linear polynomials). For tri3 and tet4 cells
     with one quadrature point, the optimized implementations do not
     use mapped cells to reduce the number of operations.

   * Scientific notation for ASCII VTK files

     Data values in ASCII data files are written in scientific notation
     with user-specified precision.

   * Nodeset names in CUBIT Exodus files

     Use of nodeset names in CUBIT Exodus files for boundary conditions
     and faults. Users can specify to use nodeset names (default
     behavior) or ids.

   * Velocity and slip rate as output fields

     Velocity (domain and subdomain) and slip rate (fault) fields are
     can be requested as output fields. The fields are computed using
     the time-stepping algorithm and alleviates the need to compute
     them via post-processing.

   * Dimensionless values in spatial databases no longer need
     artificial dimensions. Values without dimensions are understood by
     the parser as dimensionless quantities.

   * Bug fixes

     - Updating state variables did not retrieve physical properties
       for cell. Last physical properties retrieved were used. Physical
       properties are now retrieved when updating state variables.

     - Fixed incorrect dimensioning of physical properties and state
       variables for the power-law rheology in output.

     - Fixed memory bug for a fault in a 1-D mesh when constructing the
       cohesive cells.