--- name: "hwlocality_setsource" section: "3" platform: "linux" package: "hwloc" version: "2.15.0-1" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/hwlocality_setsource" --- # hwlocality\_setsource(3) Changing the Source of Topology Discovery ## NAME hwlocality\_setsource - Changing the Source of Topology Discovery ## SYNOPSIS ### Enumerations enum **hwloc\_topology\_components\_flag\_e** { **HWLOC\_TOPOLOGY\_COMPONENTS\_FLAG\_BLACKLIST** }\ ### Functions int **hwloc\_topology\_set\_pid** (**hwloc\_topology\_t** restrict topology, hwloc\_pid\_t pid)\ int **hwloc\_topology\_set\_synthetic** (**hwloc\_topology\_t** restrict topology, const char \*restrict description)\ int **hwloc\_topology\_set\_xml** (**hwloc\_topology\_t** restrict topology, const char \*restrict xmlpath)\ int **hwloc\_topology\_set\_xmlbuffer** (**hwloc\_topology\_t** restrict topology, const char \*restrict buffer, int size)\ int **hwloc\_topology\_set\_components** (**hwloc\_topology\_t** restrict topology, unsigned long flags, const char \*restrict name)\ ## Detailed Description These functions must be called between **hwloc\_topology\_init()** and **hwloc\_topology\_load()**. Otherwise, they will return -1 with errno set to EBUSY. If none of the functions below is called, the default is to detect all the objects of the machine that the caller is allowed to access. This default behavior may also be modified through environment variables if the application did not modify it already. Setting HWLOC\_XMLFILE in the environment enforces the discovery from a XML file as if **hwloc\_topology\_set\_xml()** had been called. Setting HWLOC\_SYNTHETIC enforces a synthetic topology as if **hwloc\_topology\_set\_synthetic()** had been called. Finally, HWLOC\_THISSYSTEM enforces the return value of **hwloc\_topology\_is\_thissystem()**. ## Enumeration Type Documentation ### enum hwloc\_topology\_components\_flag\_e Flags to be passed to **hwloc\_topology\_set\_components()**. **Enumerator** - ***HWLOC\_TOPOLOGY\_COMPONENTS\_FLAG\_BLACKLIST*** Blacklist the target component from being used. ## Function Documentation ### int hwloc\_topology\_set\_components (hwloc\_topology\_t restrict topology, unsigned long flags, const char \*restrict name) Prevent a discovery component from being used for a topology. name is the name of the discovery component that should not be used when loading topology topology. The name is a string such as "cuda". For components with multiple phases, it may also be suffixed with the name of a phase, for instance "linux:io". flags should be **HWLOC\_TOPOLOGY\_COMPONENTS\_FLAG\_BLACKLIST**. This may be used to avoid expensive parts of the discovery process. For instance, CUDA-specific discovery may be expensive and unneeded while generic I/O discovery could still be useful. **Returns** 0 on success. \-1 on error, for instance if flags are invalid. ### int hwloc\_topology\_set\_pid (hwloc\_topology\_t restrict topology, hwloc\_pid\_t pid) Change which process the topology is viewed from. On some systems, processes may have different views of the machine, for instance the set of allowed CPUs. By default, hwloc exposes the view from the current process. Calling **hwloc\_topology\_set\_pid()** permits to make it expose the topology of the machine from the point of view of another process. **Note** hwloc\_pid\_t is pid\_t on Unix platforms, and HANDLE on native Windows platforms. \-1 is returned and errno is set to ENOSYS on platforms that do not support this feature. The PID will not actually be used until **hwloc\_topology\_load()**. If the corresponding process exits in the meantime, hwloc will ignore the PID. If another process reuses the PID, the view of that process will be used. **Returns** 0 on success, -1 on error. ### int hwloc\_topology\_set\_synthetic (hwloc\_topology\_t restrict topology, const char \*restrict description) Enable synthetic topology. Gather topology information from the given description, a space-separated string of \ describing the object type and arity at each level. All types may be omitted (space-separated string of numbers) so that hwloc chooses all types according to usual topologies. See also the **Synthetic topologies**. Setting the environment variable HWLOC\_SYNTHETIC may also result in this behavior. If description was properly parsed and describes a valid topology configuration, this function returns 0. Otherwise -1 is returned and errno is set to EINVAL. Note that this function does not actually load topology information; it just tells hwloc where to load it from. You'll still need to invoke **hwloc\_topology\_load()** to actually load the topology information. **Returns** 0 on success. \-1 with errno set to EINVAL if the description was invalid. **Note** For convenience, this backend provides empty binding hooks which just return success. On success, the synthetic component replaces the previously enabled component (if any), but the topology is not actually modified until **hwloc\_topology\_load()**. ### int hwloc\_topology\_set\_xml (hwloc\_topology\_t restrict topology, const char \*restrict xmlpath) Enable XML-file based topology. Gather topology information from the XML file given at xmlpath. Setting the environment variable HWLOC\_XMLFILE may also result in this behavior. This file may have been generated earlier with **hwloc\_topology\_export\_xml()** in **hwloc/export.h**, or lstopo file.xml. Note that this function does not actually load topology information; it just tells hwloc where to load it from. You'll still need to invoke **hwloc\_topology\_load()** to actually load the topology information. **Returns** 0 on success. \-1 with errno set to EINVAL on failure to read the XML file. **Note** See also **hwloc\_topology\_set\_userdata\_import\_callback()** for importing application-specific object userdata. For convenience, this backend provides empty binding hooks which just return success. To have hwloc still actually call OS-specific hooks, the **HWLOC\_TOPOLOGY\_FLAG\_IS\_THISSYSTEM** has to be set to assert that the loaded file is really the underlying system. On success, the XML component replaces the previously enabled component (if any), but the topology is not actually modified until **hwloc\_topology\_load()**. If an invalid XML input file is given, the error may be reported either here or later by **hwloc\_topology\_load()** depending on the XML library used by hwloc. ### int hwloc\_topology\_set\_xmlbuffer (hwloc\_topology\_t restrict topology, const char \*restrict buffer, int size) Enable XML based topology using a memory buffer (instead of a file, as with **hwloc\_topology\_set\_xml()**). Gather topology information from the XML memory buffer given at buffer and of length size (including an ending \\0). This buffer may have been filled earlier with **hwloc\_topology\_export\_xmlbuffer()** in **hwloc/export.h**. Note that this function does not actually load topology information; it just tells hwloc where to load it from. You'll still need to invoke **hwloc\_topology\_load()** to actually load the topology information. **Returns** 0 on success. \-1 with errno set to EINVAL on failure to read the XML buffer. **Note** See also **hwloc\_topology\_set\_userdata\_import\_callback()** for importing application-specific object userdata. For convenience, this backend provides empty binding hooks which just return success. To have hwloc still actually call OS-specific hooks, the **HWLOC\_TOPOLOGY\_FLAG\_IS\_THISSYSTEM** has to be set to assert that the loaded file is really the underlying system. On success, the XML component replaces the previously enabled component (if any), but the topology is not actually modified until **hwloc\_topology\_load()**. If an invalid XML input file is given, the error may be reported either here or later by **hwloc\_topology\_load()** depending on the XML library used by hwloc. ## Author Generated automatically by Doxygen for Hardware Locality (hwloc) from the source code.