[MOAB-dev] MBInterface API changes for meshsets

[Tim Tautges]

I'm Tim Tautges and I support this message.

- tim


Jason Kraftcheck wrote:
> MOAB currently defines the following enum in MBTypes.h:
> 
>   /** Meshset options: properties for meshset creation.
>    *  Values are bit flags that may be combined with a bitwise OR (|)
>    */
>   enum MBEntitySetProperty {
>     MESHSET_TRACK_OWNER = 0x1, /**< create entity to meshset adjacencies */
>     MESHSET_SET         = 0x2, /**< set contents are unique */
>     MESHSET_ORDERED     = 0x4  /**< order of set contents is preserved */
>   };
> 
> and has the following three functions in MBInterface that interact with this
> enum:
> 
>   MBErrorCode create_meshset(const unsigned int options,
>                              MBEntityHandle &ms_handle,
>                              int start_id = 0) = 0;
> 
>   MBErrorCode get_meshset_options(const MBEntityHandle ms_handle,
>                                   unsigned int& options) const = 0;
> 
>   MBErrorCode set_meshset_options(const MBEntityHandle ms_handle,
>                                   const unsigned int options) = 0;
> 
> This API is somewhat confusing for two reasons:
>   a) We pass a bitwise-OR of the MBEntitySetProperty values an int,
>      but the latter two are mutually exclusive in the implementation.
>   b) The get/set paradigm for the options is not very convenient (and
>      potentially error prone) because one needs to get the previous
>      options and flip bits to make sure that some property (e.g.
>      tracking) isn't accidentally disabled.  For example, doing:
>       set_meshset_options( my_set, MESHSET_SET )
>      may will remove the MESHSET_TRACK_OWNER property, if it is set.
> 
> I think that the API would be easier to understand and less error prone if
> we instead had:
>   enum MBEntitySetStorage { MESHSET_SET, MESHSET_ORDERED };
> 
>   MBErrorCode create_meshset( MBEntitySetStorage type,
>                               MBEntityHandle& ms_handle,
>                               bool tracking = false,
>                               int start_id = 0 ) = 0;
> 
>   MBErrorCode get_meshset_options( MBEntityHandle ms_handle,
>                                    MBEntitySetStorage& storage,
>                                    bool& is_tracking ) = 0;
> 
>   MBErrorCode set_meshset_tracking( MBEntityHandle ms_handle,
>                                     bool tracking ) = 0;
> 
>   MBErrorCode set_meshset_storage( MBEntityHandle ms_handle,
>                                    MBEntitySetStorage type ) = 0;
> 
> Any opinions?
> 
> - jason
> 
> 

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              Tim Tautges            Argonne National Laboratory
          (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
          phone: (608) 263-8485      1500 Engineering Dr.
            fax: (608) 263-4499      Madison, WI 53706