# Changes: 2.0.17

```{rubric} General:
```

- Added support for Windows NT/95 using the Microsoft Developers
  Studio Visual C++. See the file 'Installation' for details.
- Other new machines on which this release has been tested: Cray
  T3E, SGI Origin See the file petsc/Installation for a complete
  list.

```{rubric} TS (Timestepping Solvers):
```

- Modified the pseudo-transient continuation updates:
- Changed the default update to dt =
  current_dt\*previous_fnorm/current_fnorm.
- Added the routine TSPseudoIncrementDtFromInitialDt() and the
  corresponding option -ts_pseudo_increment_dt_from_initial_dt to
  indicate use of the alternative update formula dt =
  initial_dt\*initial_fnorm/current_fnorm.
- Changed the calling sequence of TSRegister().

```{rubric} SNES (Nonlinear Solvers):
```

- Added support for computing large, sparse Jacobians efficiently
  via finite differences, see Section 5.6 (Finite Difference
  Jacobian Approximations) of the users manual.
- Added the routines SNESGetNumberLinearIterations() and
  SNESSetConvergenceHistory(). See man pages for details.
- Activated a counter of function evaluations, which is used in
  convergence tests to terminate solver if the number of function
  evaluations exceeds a given tolerance. Note: Users of matrix-free
  Newton-Krylov methods may need to reset the default allowable
  maximum (1000), via SNESSetTolerances() or -snes_max_func
  \<maxfunc>.
- Changed the calling sequence of SNESRegister().

```{rubric} SLES (Linear Solvers):
```

- See PC and KSP

```{rubric} KSP (Krylov Subspace Methods):
```

- Changed the calling sequence of KSPRegister().

```{rubric} PC (Preconditioners):
```

- Changed the calling sequence of PCRegister().
- New Additive Schwarz variants (preconditioner type PCASM)
- Added the routine PCASMSetType() (and the corresponding option
  -pc_asm_type [basic,restrict,interpolate,none]) for setting the
  variant of the additive Schwarz method. See the man page and users
  manual for details.
- Changed the default variant of PCASM from full restriction and
  interpolation to full restriction only, since this version
  requires less communication and for many problems converges faster
  than the basic variant that uses full restriction and
  interpolation. Users can still employ the basic ASM by calling
  PCASMSetType(pc,PC_ASM_BASIC) or by using the option -pc_asm_type
  basic.
- Added an interface to the SPAI preconditioner implementation of
  Steven Bernard; see src/contrib/spai. This has undergone little
  testing and optimization; it is intended mainly for "hackers".

```{rubric} MAT (Matrices):
```

- Added the matrix option,
  MatSetOption(mat,MAT_NEW_NONZERO_LOCATION_ERROR), that will cause
  an error if a new nonzero is generated in a sparse matrix.
  (currently implemented for AIJ and BAIJ matrices only). This is a
  useful flag when using SAME_NONZERO_PATTERN in calling
  SLESSetOperators() to ensure that the nonzero pattern truly does
  remain unchanged. For examples, see the programs
  petsc/src/snes/examples/tutorials/[ex5.c,ex5f.F].
- Added the routine MatSetUnfactored(), intended primarily for use
  with in-place ILU(0) factorization as a preconditioner for
  matrix-free Krylov methods. See the manual page for details.
- Added the routines MatConvertRegisterAll() and
  MatLoadRegisterAll() to allow the restriction of the matrix
  routines linked into an application code. This can decrease the
  size of your executable and the time it takes to link your
  program. For details, see the manual page and
  petsc/src/snes/examples/tutorials/ex5.c
- Added the routine MatSetValuesBlocked(), for more efficient
  assembly of block AIJ formatted matrices (MATSEQBAIJ and
  MATMPIBAIJ).
- Changed the calling sequence of MatReorderingRegister();

```{rubric} DA (Distributed Arrays):
```

- Added additional arguments to DACreate1d(), DACreate2d(), and
  DACreate3d() to allow the user to set the distribution of nodes on
  each processor; set these arguments to PETSC_NULL for the standard
  default distribution.
- Modified DAGetInfo() to return the type of periodicity.

```{rubric} VEC (Vectors):
```

- Added the routine VecCreateGhost() to create vectors that have
  ghost padding at the end of the local array. This is useful for
  gathering remote values to perform local calculations that involve
  off-processor ghost values. This is often appropriate for codes
  using unstructured grids. See
  petsc/src/vec/examples/tutorials/ex9.c for possible usage.

```{rubric} IS (Index Sets):
```

```{rubric} Draw (Graphics):
```

- Application codes should not need to use #include "draw.h" anymore
  from C/C++, since this file is now included automatically when
  "petsc.h" or any other PETSc include file is included.

```{rubric} Viewers:
```

- VIEWER_DRAWX_WORLD, VIEWER_DRAWX_SELF, VIEWER_MATLAB_WORLD are now
  supported from Fortran.
- Added VIEWER_DRAWX\_(MPI_Comm comm) from C. Useful for rapid code
  prototyping without having to declare a Viewer.

```{rubric} System Routines:
```

- Since memory leaks and uninitialized memory can be serious
  problems for large-scale application codes, we've added several
  new tools to assist in their diagnosis. These tools are all work
  in conjunction with the PETSc memory allocation (the default for
  codes that are compiled in debug mode with
  BOPT=[g,g_c++,g_complex]).
- Added the runtime option -trmalloc_log, which activates logging of
  all calls to malloc via the new routines PetscTrLog() and
  PetscTrLogDump().
- Added the routine PetscGetResidentSetSize() to determine the total
  memory used by a process (this is activated by -trmalloc_log); see
  the man page for details.
- Added the option -trmalloc_nan for tracking down allocated memory
  that is used before it has been initialized. This option calls the
  new routines PetscInitializeNans() and PetscInitializeLargeInts().
  So far these work on the Sun4 system.

```{rubric} Error Handling:
```

- The error checking macros SETERRQ() and SETERRA() now have the
  calling sequence SETERRQ(int ierr,int pierr,char \*message); where
  pierr is an additional integer error code passed to the error
  handler. Currently you should just set pierr=1.
- Also, SETERRQ() and SETERRA() now use the macro \_\_FUNC\_\_ to keep
  track of routine names. Users need not worry about this in their
  application codes, but can take advantage of this feature if
  desired by setting this macro before each user-defined routine
  that may call SETERRQ(), SETERRA(), CHKERRQ(), or CHKERRA().
  \_\_FUNC\_\_ should be set to a string containing the routine name.
  For example, #undef \_\_FUNC\_\_ #define \_\_FUNC\_\_ "MyRoutine1" int
  MyRoutine1() { /\* code here \*/ return 0; } See
  petsc/src/snes/examples/tutorials/ex3.c for an example.
- PETSc error handlers now take two additional arguments. Consult
  the man page for PetscPushErrorHandler() for more information.

```{rubric} Event Logging:
```

- Changed PLogPrintSummary(MPI_Comm,FILE \*) to
  PLogPrintSummary(MPI_Comm,char \*).
- Now the option -log_summary takes [filename] as an optional
  argument.

```{rubric} Fortran Interface:
```

- Added some limited support for direct use of Fortran90 pointers in
  the routines Vec[Get,Restore]ArrayF90(),
  Mat[Get,Restore]ArrayF90(), IS[Get,Restore]IndicesF90(),
  ISBlock[Get,Restore]IndicesF90(), VecDuplicateVecsF90(),
  VecDestroyVecsF90(), DAGetGlobalIndicesF90(). See the man pages
  and the section 'Fortran90' in the users manal for details.
  Unfortunately, these routines currently work only with the NAG F90
  compiler. We hope to support other compilers as well, but we will
  need assistance from the vendors since the Fortran90/C interface
  is not a defined standard.
- Added the macro PetscDoubleExp(a,b) = a d b (machines where double
  precision arithmetic is used) = a e b (machines where single
  precision arithmetic is used, e.g., Crays) This macro is intended
  for use only if you wish to maintain a Fortran code that is
  portable to both the Cray T3d/T3e and other Unix machines.
- For mixed Fortran/C users: added the makefile flag FCONF that may
  be used in place of the flag CONF. For an example of usage, see
  src/vec/examples/tutorials/makefile
