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_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_diff_t diff)
int hwloc_topology_diff_load_xml (const char *xmlpath,
hwloc_topology_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 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.
Differences between object 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_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_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_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_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 topology.
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
differences 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
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.
Returns
0 on success, -1 on error.
Note
the pointer returned in refname should later be freed by the
caller.
Author
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Hardware Locality (hwloc) Version 2.12.0 hwlocality_diff(3)
hwloc 2.12.0 - Generated Thu May 8 14:51:04 CDT 2025