NAME

       hwlocality_diff - Topology differences

   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_topology_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_TOPOLOGY_DIFF_OBJ_ATTR_SIZE,
           HWLOC_TOPOLOGY_DIFF_OBJ_ATTR_NAME, HWLOC_TOPOLOGY_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_topology_diff_t diff,
           unsigned long flags)
       int hwloc_topology_diff_destroy (hwloc_topology_t topology, hwloc_topology_diff_t diff)
       int hwloc_topology_diff_load_xml (hwloc_topology_t topology, const char *xmlpath,
           hwloc_topology_diff_t *diff, char **refname)
       int hwloc_topology_diff_export_xml (hwloc_topology_t topology, hwloc_topology_diff_t diff,
           const char *refname, const char *xmlpath)
       int hwloc_topology_diff_load_xmlbuffer (hwloc_topology_t topology, const char *xmlbuffer,
           int buflen, hwloc_topology_diff_t *diff, char **refname)
       int hwloc_topology_diff_export_xmlbuffer (hwloc_topology_t topology, 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 reduce 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 between topologies
       are actually supported, for instance a change in the memory size, the name of the object,
       or some info attribute. More complex differences such as adding or removing objects cannot
       be represented in the difference structures and therefore return errors.

       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_topology_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_topology_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_topology_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_topology_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_topology_diff_obj_attr_u::hwloc_topology_diff_obj_attr_s.

       HWLOC_TOPOLOGY_DIFF_TOO_COMPLEX
              The difference is too complex, it cannot be represented. The difference below this
              object has not been checked. hwloc_topology_diff_build() will return 1. The union
              is a hwloc_topology_diff_obj_attr_u::hwloc_topology_diff_too_complex_s.

Function Documentation

   int hwloc_topology_diff_apply (hwloc_topology_t topology, hwloc_topology_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_topology_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_topology_diff_destroy() (possible
           as another list).

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

       Note:
           The topology parameter must be a valid topology but it is not required that it is
           related to diff.

   int hwloc_topology_diff_export_xml (hwloc_topology_t topology, 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.

       Note:
           The topology parameter must be a valid topology but it is not required that it is
           related to diff.

   int hwloc_topology_diff_export_xmlbuffer (hwloc_topology_t topology, 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.

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

           The topology parameter must be a valid topology but it is not required that it is
           related to diff.

   int hwloc_topology_diff_load_xml (hwloc_topology_t topology, 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 topology.

       Note:
           The topology parameter must be a valid topology but it is not required that it is
           related to diff.

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

   int hwloc_topology_diff_load_xmlbuffer (hwloc_topology_t topology, const char * xmlbuffer, int
       buflen, hwloc_topology_diff_t * diff, char ** refname)
       Load a list of topology differences from a XML buffer. 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 topology.

       Note:
           The topology parameter must be a valid topology but it is not required that it is
           related to diff.

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

Author

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