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hwlocality_diff(3)	    Library Functions Manual	      hwlocality_diff(3)

NAME
     hwlocality_diff - Topology differences

SYNOPSIS
   Data Structures
     union hwloc_topology_diff_obj_attr_u
     union hwloc_topology_diff_u

   Typedefs
     typedef	  enum	    hwloc_topology_diff_obj_attr_type_e     hwloc_topol-
	 ogy_diff_obj_attr_type_t
     typedef enum hwloc_topology_diff_type_e hwloc_topology_diff_type_t
     typedef union hwloc_topology_diff_u * hwloc_topology_diff_t

   Enumerations
     enum	hwloc_topology_diff_obj_attr_type_e	   {	    HWLOC_TOPOL-
	 OGY_DIFF_OBJ_ATTR_SIZE, HWLOC_TOPOLOGY_DIFF_OBJ_ATTR_NAME, HWLOC_TOPOL-
	 OGY_DIFF_OBJ_ATTR_INFO }
     enum     hwloc_topology_diff_type_e     {	   HWLOC_TOPOLOGY_DIFF_OBJ_ATTR,
	 HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX }
     enum hwloc_topology_diff_apply_flags_e {  HWLOC_TOPOLOGY_DIFF_APPLY_REVERSE
	 }

   Functions
     int  hwloc_topology_diff_build (hwloc_topology_t topology, hwloc_topology_t
	 newtopology, unsigned long flags, hwloc_topology_diff_t *diff)
     int  hwloc_topology_diff_apply  (hwloc_topology_t	topology,   hwloc_topol-
	 ogy_diff_t diff, unsigned long flags)
     int hwloc_topology_diff_destroy (hwloc_topology_diff_t diff)
     int   hwloc_topology_diff_load_xml   (const   char  *xmlpath,  hwloc_topol-
	 ogy_diff_t *diff, char **refname)
     int hwloc_topology_diff_export_xml (hwloc_topology_diff_t diff, const  char
	 *refname, const char *xmlpath)
     int  hwloc_topology_diff_load_xmlbuffer (const char *xmlbuffer, int buflen,
	 hwloc_topology_diff_t *diff, char **refname)
     int hwloc_topology_diff_export_xmlbuffer (hwloc_topology_diff_t diff, const
	 char *refname, char **xmlbuffer, int *buflen)

Detailed Description
     Applications that manipulate many similar topologies, for instance one  for
     each  node of a homogeneous cluster, may want to compress topologies to re-
     duce the memory footprint.

     This file offers a way to manipulate the difference between topologies  and
     export/import  it	to/from  XML.  Compression  may therefore be achieved by
     storing one topology entirely while the others are only described by  their
     differences  with the former. The actual topology can be reconstructed when
     actually needed by applying the precomputed  difference  to  the  reference
     topology.

     This interface targets very similar nodes. Only very simple differences be-
     tween  topologies are actually supported, for instance a change in the mem-
     ory size, the name of the object, or some info attribute. More complex dif-
     ferences such as adding or removing objects cannot be  represented  in  the
     difference  structures and therefore return errors. Differences between ob-
     ject sets or topology-wide allowed sets, cannot be represented either.

     It means that there is no need to apply the difference when looking at  the
     tree  organization  (how many levels, how many objects per level, what kind
     of objects, CPU and node sets, etc) and when binding  to  objects.  However
     the  difference  must  be applied when looking at object attributes such as
     the name, the memory size or info attributes.

Typedef Documentation
   typedef	enum	  hwloc_topology_diff_obj_attr_type_e	    hwloc_topol-
     ogy_diff_obj_attr_type_t
     Type of one object attribute difference.

   typedef union hwloc_topology_diff_u * hwloc_topology_diff_t
     One element of a difference list between two topologies.

   typedef enum hwloc_topology_diff_type_e hwloc_topology_diff_type_t
     Type of one element of a difference list.

Enumeration Type Documentation
   enum hwloc_topology_diff_apply_flags_e
     Flags to be given to hwloc_topology_diff_apply().

     Enumerator

     HWLOC_TOPOLOGY_DIFF_APPLY_REVERSE
	    Apply topology diff in reverse direction.

   enum hwloc_topology_diff_obj_attr_type_e
     Type of one object attribute difference.

     Enumerator

     HWLOC_TOPOLOGY_DIFF_OBJ_ATTR_SIZE
	    The  object  local	memory	is modified. The union is a hwloc_topol-
	    ogy_diff_obj_attr_u::hwloc_topology_diff_obj_attr_uint64_s (and  the
	    index field is ignored).

     HWLOC_TOPOLOGY_DIFF_OBJ_ATTR_NAME
	    The   object   name   is  modified.  The  union  is  a  hwloc_topol-
	    ogy_diff_obj_attr_u::hwloc_topology_diff_obj_attr_string_s (and  the
	    name field is ignored).

     HWLOC_TOPOLOGY_DIFF_OBJ_ATTR_INFO
	    the  value	of  an	info  attribute  is  modified.	The  union  is a
	    hwloc_topology_diff_obj_attr_u::hwloc_topol-
	    ogy_diff_obj_attr_string_s.

   enum hwloc_topology_diff_type_e
     Type of one element of a difference list.

     Enumerator

     HWLOC_TOPOLOGY_DIFF_OBJ_ATTR
	    An object  attribute  was  changed.  The  union  is  a  hwloc_topol-
	    ogy_diff_u::hwloc_topology_diff_obj_attr_s.

     HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX
	    The difference is too complex, it cannot be represented. The differ-
	    ence   below   this   object  has  not  been  checked.  hwloc_topol-
	    ogy_diff_build()  will  return  1.	The  union  is	a   hwloc_topol-
	    ogy_diff_u::hwloc_topology_diff_too_complex_s.

Function Documentation
   int	 hwloc_topology_diff_apply   (hwloc_topology_t	 topology,  hwloc_topol-
     ogy_diff_t diff, unsigned long flags)
     Apply a topology diff to an existing topology. flags is  an  OR'ed  set  of
     hwloc_topology_diff_apply_flags_e.

     The  new topology is modified in place. hwloc_topology_dup() may be used to
     duplicate it before patching.

     If the difference cannot be applied entirely, all previous applied elements
     are unapplied before returning.

     Returns
	 0 on success.

	 -N if applying the difference failed while trying  to	apply  the  N-th
	 part  of  the difference. For instance -1 is returned if the very first
	 difference element could not be applied.

   int hwloc_topology_diff_build  (hwloc_topology_t  topology,	hwloc_topology_t
     newtopology, unsigned long flags, hwloc_topology_diff_t * diff)
     Compute  the difference between 2 topologies. The difference is stored as a
     list of hwloc_topology_diff_t entries starting at diff. It is  computed  by
     doing a depth-first traversal of both topology trees simultaneously.

     If  the  difference between 2 objects is too complex to be represented (for
     instance if some objects have different  types,  or  different  numbers  of
     children),  a special diff entry of type HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX is
     queued. The computation of the diff does not continue below these	objects.
     So  each  such  diff  entry  means that the difference between two subtrees
     could not be computed.

     Returns
	 0 if the difference can be represented properly.

	 0 with diff pointing to NULL if there	is  no	difference  between  the
	 topologies.

	 1  if	the  difference  is too complex (see above). Some entries in the
	 list will be of type HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX.

	 -1 on any other error.

     Note
	 flags is currently not used. It should be 0.

	 The output diff has to be freed with hwloc_topology_diff_destroy().

	 The output diff can only be exported to XML or passed	to  hwloc_topol-
	 ogy_diff_apply()   if	0  was	returned,  i.e.  if  no  entry	of  type
	 HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX is listed.

	 The output diff may be modified by removing some entries from the list.
	 The removed entries should be freed by passing them to to  hwloc_topol-
	 ogy_diff_destroy() (possible as another list).

   int hwloc_topology_diff_destroy (hwloc_topology_diff_t diff)
     Destroy a list of topology differences.

     Returns
	 0.

   int	hwloc_topology_diff_export_xml (hwloc_topology_diff_t diff, const char *
     refname, const char * xmlpath)
     Export a list of topology differences to a XML file. If not  NULL,  refname
     defines an identifier string for the reference topology which was used as a
     base when computing this difference. This identifier is usually the name of
     the  other XML file that contains the reference topology. This attribute is
     given back when reading the diff from XML.

     Returns
	 0 on success, -1 on error.

   int hwloc_topology_diff_export_xmlbuffer (hwloc_topology_diff_t  diff,  const
     char * refname, char ** xmlbuffer, int * buflen)
     Export a list of topology differences to a XML buffer. If not NULL, refname
     defines an identifier string for the reference topology which was used as a
     base when computing this difference. This identifier is usually the name of
     the  other XML file that contains the reference topology. This attribute is
     given back when reading the diff from XML.

     The returned buffer ends with a \0 that is included in the returned length.

     Returns
	 0 on success, -1 on error.

     Note
	 The XML buffer should later be freed with hwloc_free_xmlbuffer().

   int hwloc_topology_diff_load_xml (const char * xmlpath, hwloc_topology_diff_t
     * diff, char ** refname)
     Load a list of topology differences from a XML file. If not  NULL,  refname
     will be filled with the identifier string of the reference topology for the
     difference  file,	if any was specified in the XML file. This identifier is
     usually the name of the other XML file that contains the  reference  topol-
     ogy.

     Returns
	 0 on success, -1 on error.

     Note
	 the pointer returned in refname should later be freed by the caller.

   int	hwloc_topology_diff_load_xmlbuffer  (const char * xmlbuffer, int buflen,
     hwloc_topology_diff_t * diff, char ** refname)
     Load a list of topology differences from a XML buffer. Build a list of dif-
     ferences from the XML memory buffer given at xmlbuffer and of length buflen
     (including an ending \0). This buffer may have  been  filled  earlier  with
     hwloc_topology_diff_export_xmlbuffer().

     If  not NULL, refname will be filled with the identifier string of the ref-
     erence topology for the difference file, if any was specified  in	the  XML
     file.  This  identifier is usually the name of the other XML file that con-
     tains the reference topology.

     Returns
	 0 on success, -1 on error.

     Note
	 the pointer returned in refname should later be freed by the caller.

Author
     Generated automatically by Doxygen for Hardware Locality (hwloc)  from  the
     source code.

Hardware Locality (hwloc)	 Version 2.12.1 	      hwlocality_diff(3)

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