# PyLith Development Plan, June 2019

## Version 3.0.0beta3 (June 2019)

* Prescribed slip for faults with buried edges [90%]
* Clean up of examples [50%]
* Other bugfixes

## Version 2.2.2 (July 2019)

* Add ability to output residual field during nonlinear solve for debugging ![easy](images/easy.png)

* Release bugfixes

  * Fix material deallocation memory issue.
  * Fix PETSc version test for tagged release.

## Version 3.0.0 (August 2019)

* Multiphysics
  * Implement modular approach for specifying governing equations and computing residuals and Jacobians. ![expert](images/expert.png) [100%]
  * Incompressible elasticity via a pressure field  ![intermediate](images/intermediate.png) [95%]

* Higher order basis functions ![difficult](images/difficult.png) [100%]

  Allow user to select order of basis functions independent of the mesh (which defines the geometry). This permits higher resolution for a given mesh.

* Switch to using PETSc time-stepping (TS) algorithms for quasi-static simulations. ![intermediate](images/intermediate.png) [100%]

  Replace simple Python-based time-stepping implementations with PETSc time-stepping algorithms that provide support for higher order discretization in time and real adaptive time stepping.

* Modular approach for initial conditions ![intermediate](images/intermediate.png) [100%]

* Testing via Method of Manufactured Solutions ![difficult](images/difficult.png) [80%]

## Version 3.1 (June, 2020)

* Use PETSc time-stepping (TS) algorithms for dynamic simulations. ![intermediate](images/intermediate.png) [50%]

* Improve fault formulation for spontaneous rupture ![expert](images/expert.png) [10%]

  Removes inner solve associated with updating Lagrange multipliers. This will significantly accelerate the nonlinear solve.

* Convert to Python 3 ![difficult](images/difficult.png) 

* Reorganize output for time-dependent Green's functions and adjoints ![intermediate](images/intermediate.png)  

* Poroelasticity  [15%] ![difficult](images/difficult.png)

  Contribution led by Josimar da Silva and Robert Walker.

* Parallel mesh loading ![expert](images/expert.png)

  Requires creating cohesive cells in parallel.

* Integration with libCEED for fast high order residual evaluation in dynamic simulations ![expert](images/expert.png)

  Contribution led by Jed Brown.

## Version 3.2

* Earthquake cycle modeling  ![expert](images/expert.png)

  (dynamic → quasi-static, quasi-static → dynamic, complete cycle)

* Reimplementation of small strain formulation  ![intermediate](images/intermediate.png)

* Moment tensor point sources  [5%]

  Moment tensor point sources provide a mesh independent deformation source that is better suited for Green's function calculations than slip on a fault surface via cohesive cells.

## Features for Future Releases

* Drucker-Prager bulk rheology with relaxation to yield surface ![intermediate](images/intermediate.png) 
* Create strain hardening/softening 2-D and 3-D Drucker-Prager elastoplastic models.  ![intermediate](images/intermediate)
* Elasticity + heat flow  ![intermediate](images/intermediate.png) 
* Multilevel nonlinear solve  ![expert](images/expert.png) 
* Radial basis functions for spatial databases  ![difficult](images/difficult.png) 
* Adaptive mesh refinement ![expert](images/expert.png)
* Adjoint for data assimilation ![difficult](images/difficult.png)
* Combined prescribed slip / spontaneous rupture fault condition ![difficult](images/difficult.png)

    Use fault constitutive model to control slip on fault except during episodes of prescribed slip. Need some way to describe when to turn on/off prescribed slip.