HWLOC-DIFF(1) hwloc HWLOC-DIFF(1)

# [NAME](#NAME)

hwloc-diff - Compute differences between two XML topologies

# [SYNOPSIS](#SYNOPSIS)

**hwloc-diff** \[*options*] *<input1.xml>* *<input2.xml>*

**hwloc-diff** \[*options*] *<input1.xml>* *<input2.xml>* *<output.xml>*

# [OPTIONS](#OPTIONS)

[**--refname** <name>](#refname)

Use <name> as the identifier for the reference topology in the output XML difference. It is meant to tell which topology should be used when applying the resulting difference. hwloc-patch may use that name to automatically load the relevant reference topology XML. By default, <input1.xml> is used without its full path.

[**--version**](#version)

Report version and exit.

[**-h** **--help**](#h)

Display help message and exit.

# [DESCRIPTION](#DESCRIPTION)

hwloc-diff computes the difference between two XML topologies and stores the result into <output.xml> if any, or dumps it to stdout otherwise.

The output difference may later be applied to another topology with hwloc-patch.

hwloc-compress-dir may be used for computing the diffs between all XML files in a directory.

**NOTE:** If some application-specific userdata were been exported to the input XMLs, they will be ignored and discarded from the output because hwloc has no way to understand and compare them.

**NOTE:** It is highly recommended that you read the [hwloc(7)](/man/os/hwloc/hwloc.7) overview page before reading this man page. Most of the concepts described in [hwloc(7)](/man/os/hwloc/hwloc.7) directly apply to the hwloc-diff utility.

# [EXAMPLES](#EXAMPLES)

hwloc-diff's operation is best described through several examples.

Compute the difference between two XML topologies and output it to stdout:

$ hwloc-diff fourmi023.xml fourmi024.xml  
Found 11 differences, exporting to stdout  
<?xml version="1.0" encoding="UTF-8"?>  
...

Output the difference to file diff.xml instead:

$ hwloc-diff fourmi023.xml fourmi024.xml diff.xml  
Found 11 differences, exporting to diff.xml

When the difference is too complex to be represented:

$ hwloc-diff fourmi023.xml avakas-frontend1.xml  
Found 1 differences, including 1 too complex ones.  
Cannot export differences to stdout

Directly compute the difference between two topologies and apply it to another one:

$ hwloc-diff fourmi023.xml fourmi024.xml | hwloc-patch fourmi025.xml -

# [RETURN VALUE](#RETURN_VALUE)

Upon successful execution, hwloc-diff outputs the difference. The return value is 0.

If the difference is too complex to be represented, an error is returned and the output is not generated.

hwloc-diff also returns nonzero if any kind of error occurs, such as (but not limited to) failure to parse the command line.

# [SEE ALSO](#SEE_ALSO)

[hwloc(7)](/man/os/hwloc/hwloc.7), [lstopo(1)](/man/os/hwloc/lstopo.1), [hwloc-patch(1)](/man/os/hwloc/hwloc-patch.1), [hwloc-compress-dir(1)](/man/os/hwloc/hwloc-compress-dir.1)

Unreleased developer copy 2.15.0rc2-git

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Document: hwloc-diff(1) from hwloc 2.15.0-r1 (Chainguard OS)
Source: https://github.com/open-mpi/hwloc