.\" -*- nroff -*-
.\" Copyright © 2013-2018 Inria.  All rights reserved.
.\" See COPYING in top-level directory.
.TH HWLOC-DIFF "1" "Nov 23, 2023" "2.10.0rc2" "hwloc"
.SH NAME
hwloc-diff \- Compute differences between two XML topologies
.
.\" **************************
.\"    Synopsis Section
.\" **************************
.SH SYNOPSIS
.
.PP
.B hwloc-diff
[\fIoptions\fR]
\fI<input1.xml>\fR
\fI<input2.xml>\fR
.PP
.B hwloc-diff
[\fIoptions\fR]
\fI<input1.xml>\fR
\fI<input2.xml>\fR
\fI<output.xml>\fR
.
.\" **************************
.\"    Options Section
.\" **************************
.SH OPTIONS
.
.TP 10
\fB\-\-refname\fR <name>
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.
.TP
\fB\-\-version\fR
Report version and exit.
.TP
\fB\-h\fR \fB\-\-help\fR
Display help message and exit.
.
.\" **************************
.\"    Description Section
.\" **************************
.SH 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.
.
.PP
The output difference may later be applied to another topology
with hwloc-patch.
.
.PP
hwloc-compress-dir may be used for computing the diffs between
all XML files in a directory.
.
.PP
.B 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.
.
.PP
.B NOTE:
It is highly recommended that you read the hwloc(7) overview page
before reading this man page.  Most of the concepts described in
hwloc(7) directly apply to the hwloc-diff utility.
.
.\" **************************
.\"    Examples Section
.\" **************************
.SH EXAMPLES
.PP
hwloc-diff's operation is best described through several examples.
.
.PP
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 section
.\" **************************
.SH RETURN VALUE
Upon successful execution, hwloc-diff outputs the difference.
The return value is 0.
.
.PP
If the difference is too complex to be represented, an error is returned
and the output is not generated.
.
.PP
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 section
.\" **************************
.SH SEE ALSO
.
.ft R
hwloc(7), lstopo(1), hwloc-patch(1), hwloc-compress-dir(1)
.sp