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dev:codingconventions [2016/03/16 13:10]
pseewald Added docu for new prettify
dev:codingconventions [2020/05/05 07:51]
oschuett
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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 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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     * INTEGER i=4.9999, i.e. i=INT(4.9999) implies i==4. Use NINT(4.9999) as appropriate.     * INTEGER i=4.9999, i.e. i=INT(4.9999) implies i==4. Use NINT(4.9999) as appropriate.
     * natom*natom, nrow_global*ncol_global overflows INT(KIND=4) for large simulations.     * natom*natom, nrow_global*ncol_global overflows INT(KIND=4) for large simulations.
 +    * always use REAL() with KIND parameter, i.e. r = REAL(i, KIND=dp).
 +    * avoid FLOAT() in favour of REAL(, KIND=dp).
     * the global number of grid points (pw_grid_type%ngpts,ngpts_cut) overflows INT(KIND=4) for large simulations.     * the global number of grid points (pw_grid_type%ngpts,ngpts_cut) overflows INT(KIND=4) for large simulations.
  
 ===== 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 =====
-For many common operation there exist wrappers in CP2K to prevent usage errors and to allow for central redirections.+ 
 +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 
   * 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.
   * Use the routines from ''message_passing.F'' instead of calling MPI directly.   * Use the routines from ''message_passing.F'' instead of calling MPI directly.
 +  * Use the routines from ''fft_lib.F'' instead of calling FFT (any library) directly.
   * Use the routines from ''machine.F'' to access architecture depended things like e.g. the working directory.   * Use the routines from ''machine.F'' to access architecture depended things like e.g. the working directory.
   * Don't use ''UNIT=*'' in ''WRITE'' or ''PRINT'' statements. Instead request a unit from the logger: ''iw=cp_logger_get_default_unit_nr()'' and write only if you actually received a unit: ''IF(iw>0) WRITE (UNIT=iw, ,,,)''.   * Don't use ''UNIT=*'' in ''WRITE'' or ''PRINT'' statements. Instead request a unit from the logger: ''iw=cp_logger_get_default_unit_nr()'' and write only if you actually received a unit: ''IF(iw>0) WRITE (UNIT=iw, ,,,)''.
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   * Each module and routine should be annotated with [[dev:codingconventions#Doxygen| Doxygen documentation]].   * Each module and routine should be annotated with [[dev:codingconventions#Doxygen| Doxygen documentation]].
   * Each preprocessor flag should start with two underscores and be documented in the ''INSTALL''-file and added to the cp2k_flags function (cp2k_info.F).   * Each preprocessor flag should start with two underscores and be documented in the ''INSTALL''-file and added to the cp2k_flags function (cp2k_info.F).
-  * The code should be formatted with the prettify-tool by running ''make -j pretty''. +  * The code should be formatted with the [[dev:formattingconventions| prettify tool]] by running ''make -j pretty''.
 ===== Write tests ===== ===== Write tests =====
   * Every feature should be tested, with the goal of complete [[ http://www.cp2k.org/static/coverage/ | code coverage by regtesting ]].   * Every feature should be tested, with the goal of complete [[ http://www.cp2k.org/static/coverage/ | code coverage by regtesting ]].
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   * Please run ''make doxify'' to format your doxygen comments, or generate templates where none exist   * Please run ''make doxify'' to format your doxygen comments, or generate templates where none exist
   * See our [[ http://doxygen.cp2k.org/files.html | doxygen pages ]] for the result   * See our [[ http://doxygen.cp2k.org/files.html | doxygen pages ]] for the result
- 
-===== Formatting conventions and auto-formatting (prettify) ===== 
-Uniform formatting of CP2K source code will be enabled in the near future by a prettify script that is an almost complete auto-formatter for Fortran 90 source code. As a rule of thumb, developers should not worry about the format of their code and just let prettify do its magic by running ''make -j pretty''. The chosen formatting conventions for CP2K are as follows: 
-  * Sorting and alignment of variable declarations and ''USE'' statements, removal of unused list entries. 
-  * Indentation with a relative width of 3 characters. 
-  * Line continuations are aligned with the previous opening delimiter ''('', ''['' or ''(/'' or with an assignment operator ''='' or ''%%=>%%''. If none of the above is present, a default hanging indent of 3 characters is applied. 
-  * All operators are surrounded by exactly one whitespace character, except for arithmetic operators. 
-  * Removal of extraneous whitespace and consecutive blank lines. 
-  * Uppercase notation for all Fortran and OpenMP keywords. 
-The following formatting decisions are still manual and are never changed by prettify: 
-  * Positions of line breaks (except for variable declarations and ''USE'' statements). 
-  * No indentation of subsequent ''DO'' / ''IF'' statements that are aligned with each other. 
-There may be cases where manual alignment is preferred over the rules stated above. The following options for manual formatting are provided: 
-  * No automatic realignment of line continuations that are prefixed with an ''&''. 
-  * No auto-formatting of lines to which a comment starting with ''!&'' is attached. 
-  * No auto-formatting of code blocks enclosed between two comment lines starting with ''!&<'' and ''!&>''. 
- 
-A few examples to illustrate how to deal with cases where auto-formatting produces unsatisfying results: 
- 
-  * Reduce hanging indent by inserting linebreaks directly after assignment operator and opening delimiter: 
-<code fortran> 
-! No: 
-long_result_var_name = long_function_name(arg_1, arg_2, & 
-                                          arg_3, arg_4, arg_5)+ & 
-                       foo 
-! Yes: 
-long_result_var_name = & 
-   long_function_name( & 
-      arg_1, arg_2, & 
-      arg_3, arg_4, arg_5)+ & 
-   foo 
-</code> 
-  * Avoid linebreaks in deeply nested expressions: 
-<code fortran> 
-! No: 
-bessj0 = (r1+y*(r2+y*(r3+y*(r4+y* & 
-                            (r5+y*r6)))))/(s1+y*(s2+y*(s3+y* & 
-                                                       (s4+y*(s5+y*s6))))) 
-! Yes: 
-bessj0 = (r1+y*(r2+y*(r3+y*(r4+y*(r5+y*r6)))))/ & 
-         (s1+y*(s2+y*(s3+y*(s4+y*(s5+y*s6))))) 
-</code> 
-  * Alignment by explicit bracketing: 
-<code fortran> 
-! No: 
-foo = bar+foobar(x1, y1, z1)* & 
-      foobar(x2, y2, z2)* & 
-      foobar(x3, y3, z3) 
-! Yes: 
-foo = bar+(foobar(x1, y1, z1)* & 
-           foobar(x2, y2, z2)* & 
-           foobar(x3, y3, z3)) 
-</code> 
-  * Special vertical alignment may require manual formatting: 
-<code fortran> 
-! Auto-formatting: 
-align_me = [-1, 10, 0, & 
-            0, 1000, 0, & 
-            0, -1, 1] 
-! Manual alignment (!& disables whitespace formatting): 
-align_me = [-1,   10, 0, & !& 
-             0, 1000, 0, & !& 
-             0,   -1, 1] !& 
-! Alternatively: 
-!&< 
-align_me = [-1,   10, 0, & 
-             0, 1000, 0, & 
-             0,   -1, 1] 
-!&> 
-</code> 
dev/codingconventions.txt · Last modified: 2020/08/21 10:15 (external edit)