petsc-3.12.4 2020-02-04
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# Documentation: Changes: 3.11

## CHANGES in the PETSc 3.11 Version

#### General:

#### Configure/Build:

- Configure now supports Python 3.4+ in addition to Python 2.6+.

#### IS:

#### PetscDraw:

#### PF:

#### Vec:

#### VecScatter:

- Removed VecScatterCreateEmpty(MPI_Comm,VecScatter*)
- Added a PetscSF implementation of VecScatter. One can enable it with -vecscatter_type sf

#### PetscSection:

#### Mat:

- MatRegisterBaseName() changed to MatRegisterRootName()
- Added -mat_mffd_complex to use complex number trick instead of differencing to evaluate product; requires real functions but complex configuration
- Added initial support for HDF5 files I/O, particularly MATLAB MAT-File Version 7.3, currently only for reading. See also documentation of MatLoad().

#### PC:

- PCGetSetUpFailedReason is now PCGetFailedReason()

#### KSP:

- KSP_DIVERGED_PCSETUP_FAILED replaced with KSP_DIVERGED_PC_FAILED
- Previously the KSP Chebyshev implementation always did one more iteration than requested. For example -ksp_max_it 2 resulted in 3 Chebyshev iterations. This has been corrected. Due to this correction your solver may seem to converge more slowely than it previous has. Note that the multigrid solvers (PCMG, PCGAMG, PCML) used by default Chebyshev (with 3 actual steps) in their smoother, thus the multigrid solvers will now have seemingly different convergence rates since they will now use only 2 actual steps. To reproduce previous behavior change the number of smoother iterations to match the previous actual amount, this can be done with for example -mg_levels_ksp_max_it 3 (or -prefix_mg_levels_ksp_max_it 3 if the KSP object has a prefix).

#### SNES:

- Added SNESKSPTRANSPOSEONLY: a linear solver only SNES that solves the transposed linear system.

#### SNESLineSearch:

#### TS:

- Added TSADAPTHISTORY: a new TSAdapt implementation that follows a given time history, that can set with TSAdaptHistorySetHistory().
- Added TSTrajectoryGetVecs() to reconstructs states and time derivative vectors from a TSTrajectory.

#### TAO:

- Added extra void* (context) pointer to the function prototype to be passed as user-defined update function to TaoSetUpdate().

#### DM/DA:

- Added DMStag and associated functions, for working with quantities on regular staggered grids, in a manner similar to the usage of DMDA for colocated quantities.
- Added DMLocalToGlobal() and DMLocalToGlobal()

#### DMPlex:

- Reorganized PetscDS handling completely in order to support multiple subdomains. DMSetDS() was removed in favor of DMSetField()+DMCreateDS().
- Added additional PetscSF* return argument to DMPlexGetGatherDM() (made public) and DMPlexGetRedundantDM().

#### PetscViewer:

- Added new command line options to GLVis viewer, see PetscViewerGLVisOpen() manual page for details.
- PetscViewerHDF5{Has,Read,Write}Attribute():
  - take the input path as relative to the current (pushed) group
  - support not only dataset attributes but also group attributes
  - PetscViewerHDF5WriteAttribute() creates the group if it doesn't exist
  - PetscViewerHDF5HasAttribute() returns false if the parent path doesn’t exist instead of failing
- Added PetscViewerHDF5Has{Group,Object}()
- Added PetscViewerHDF5{Has,Write,Read}ObjectAttribute()
- PetscViewerHDF5OpenGroup() opens the root group (/) if none is pushed

#### SYS:

- PetscOptionsGetViewer() takes a NULL or PetscOptions object as the second argument.

#### AO:

#### Sieve:

#### Fortran: