- the problem arises when output fields are missing on some
  processors.

  When the information is combined, the resulting HashTables can have
  different insertion orders. This poses an issue when there are hash
  key collisions and thus different chaining.

- Use sorted order.

mattijs authored Sep 30, 2020 and Mark OLESEN committed Sep 30, 2020

Triggered when running e.g. postProcess

- specifying gradientExpr without a valueExpr, a missing fractionExpr
  should be treated as 0 (gradient only), not as 1 (value only)

ENH: improve sanity checks + evaluation short-cuts in exprMixedFvPatchField

- incorrect branching logic caused the "0" case to be ignored

- mostly only tripped when using fractional edge grading, since this
  is where the list reading is used. Overseen in commit 7da0b5be.

- the various information queries MUST be executed with
  the '--no-print-directory' or risk polluting values
  in the information queries.

  This is mostly seen with the 'canCompile' test for tutorials running
  in parallel.

- backported fix from develop

COMP: incorrect variable names in PtrListOpsTemplates.C

- used fluidThermo::typeName instead of fluidThermo::dictName
  within the Cp() method.

- only checked if it started with '/' and not 'd:/' (for example).

- improves build robustness, even with a reduced environment (#517)

ENH: improve cmake/ParaView config handling

See merge request !358

- improve handling of changes in ParaView/VTK or cmake parameters (#1693)

  * adjust internals to support recording of an unlimited number of
    configuration parameters and use file `cmp` instead of trying
    to check strings ourselves.

ENH: new wmake/scripts/wmake.cmake-args handler

- additional handling of -prefix=... as CMAKE_INSTALL_PREFIX export.

- in some contexts, can use instead of AllwmakeParseArguments

- an otherwise confusing amount of output that may not be expected

- bin/tools/create-mpi-config to query/write values for system openmpi.
  In some cases this can be used to avoid an mpicc requirement at runtime.

- adjust openfoam session to include -test-tutorial forwarding to the
  tutorials/AutoTest. This helps with writing installation tests.

- adjust foamConfigurePaths to latest version

- removal of gperftools default config, as per develop

- remove MSWindows components (code and makefiles)

- use cxx, hxx extensions to reduce possible confusion with other
  "list" and "vector" classes

- use C++ versions for C headers

- inadvertently set to zero instead of one (in commit 1d85fecf)

- align wmake have_* scripts to support version query as per current
  develop branch

- use config.sh/ fallbacks when the corresponding *_ARCH_PATH is empty
  (eg, BOOST, CGAL, FFTW).
  This aids when building outside of the regular OpenFOAM environment.

- add '[-+.~]' to the recognized qualifiers.
  This allows simple readable names such as

      WM_COMPILER=Clang-vendor

  but also opens the FUTURE (not yet supported) possibility of
  combining in additional information. For example,

      WM_COMPILER=Clang~openmp
      WM_COMPILER=Clang+cuda~openmp

  by using '+' (add) and '~' (subtract) notation similar to what
  spack uses.

CONFIG: support 'override' rules

- if present, compiler-family 'override' rules are included after
  compiler-family 'general' rules have been included. This allows a
  central means for including dynamically generated content to
  override some values.

  Some examples:

  To handle different gcc versions (system compiler):

  wmake/rules/...Gcc/override

  ```
  ifneq (,$(findstring 9, $(WM_COMPILER)))
      cc  := gcc-9
      CC  := g++-9 -std=c++11
  endif
  ```

  To handle different openmp on Darwin (#1656):

  wmake/rules/darwin64Clang/override

  ```
  # Use libomp (not libgomp) unless openmp is disabled
  ifeq (,$(findstring "~openmp", "$(WM_COMPILER)"))
      COMP_OPENMP = -DUSE_OMP -Xpreprocessor -fopenmp
      LINK_OPENMP = -lomp
  else
      include $(GENERAL_RULES)/no-openmp
  endif
  ```

  This treatment arguably fits into wmake/rules/darwin64Clang/general,
  but it serves to illustrate a possible use case.

- requires -Xpreprocessor
- uses 'libomp' (no 'libgomp' link)

- can aid when creating source-only or binary-only packages

- eg, for a uniform field and auto range.