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dev:codingconventions

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dev:codingconventions [2018/01/11 15:31] – [Use existing infrastructure] 130.60.136.207dev:codingconventions [2020/08/21 10:15] (current) – external edit 127.0.0.1
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 ====== Coding Conventions ====== ====== Coding Conventions ======
 +
 ===== Stick to the standard ===== ===== Stick to the standard =====
-  * Code enabled by default should be standard Fortran2003 [-std=f2003] + 
-  * Avoid using new OOP aspects, because compilers do not yet support them well enough. +  * Code enabled by default should be standard Fortran 2008 [-std=f2008] and C99 [-std=c99] 
-  * OpenMP code should follow the version 3.X of the standard +  * OpenMP code should follow version 3.X of the standard 
-  * MPI should should follow the version 2.X of the standard +  * MPI should should follow version 3 of the standard 
-  * Extended functionality should match [[wp>POSIX]] / [[wp>Linux_Standard_Base|LSB]].+  * Extended functionality should match [[wp>POSIX]] and [[wp>Linux_Standard_Base|LSB]].
  
 ===== Write explicit code ===== ===== Write explicit code =====
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 ===== Don't use poorly designed language features ===== ===== Don't use poorly designed language features =====
   * Do not use the ''GOTO''-statement. See also [[http://xkcd.com/292/]] and [[doi>10.1145/362929.362947]]   * Do not use the ''GOTO''-statement. See also [[http://xkcd.com/292/]] and [[doi>10.1145/362929.362947]]
-  * Do not use left-hand-side (lhs) reallocations of allocatables [-Wrealloc-lhs-all]. [[http://www.tddft.org/pipermail/octopus-devel/2012-February/005510.html | Why? ]] +  * Do not use left-hand-side (lhs) reallocations of allocatables [-Wrealloc-lhs]. [[https://github.com/cp2k/cp2k/issues/726 | Why? ]] 
   * Do not use ''FORALL'' constructs. [[https://gcc.gnu.org/ml/fortran/2012-04/msg00025.html | Why? ]]   * Do not use ''FORALL'' constructs. [[https://gcc.gnu.org/ml/fortran/2012-04/msg00025.html | Why? ]]
   * Do not use ''OMP THREADPRIVATE'' variables.   * Do not use ''OMP THREADPRIVATE'' variables.
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 ===== Use existing infrastructure ===== ===== Use existing infrastructure =====
 +
 +Always prefer [[https://gcc.gnu.org/onlinedocs/gcc-8.2.0/gfortran/Intrinsic-Procedures.html|built-in (intrinsic) functions]] instead of hand-coded routines since they usually include extra numerical checks to avoid intermediate under- or overflow while still performing optimally. Examples:
 +
 +  * ''NORM2(x)'' instead of ''%%SQRT(x(1)**2 + x(2)**2 + x(3)**2)%%''
 +  * ''DOT_PRODUCT(x, x)'' instead of ''%%x(1)**2 + x(2)**2 + x(3)**2%%''
 +  * ''DOT_PRODUCT(x, y)'' instead of ''%%x(1)*y(1) + x(2)*y(2) + x(3)*y(3)%%''
 +
 +
 For many common operations there exist wrappers in CP2K to prevent usage errors and to allow for central redirections, i.e. avoid to use direct calls to external libraries in CP2K For many common operations there exist wrappers in CP2K to prevent usage errors and to allow for central redirections, i.e. avoid to use direct calls to external libraries in CP2K
 +
   * Use the routines from ''cp_files.F'' instead of calling ''OPEN'' and ''CLOSE'' directly.   * Use the routines from ''cp_files.F'' instead of calling ''OPEN'' and ''CLOSE'' directly.
   * Use the routines from the full-matrix ''fm''-package instead of calling BLAS or Scalapack directly.   * Use the routines from the full-matrix ''fm''-package instead of calling BLAS or Scalapack directly.
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