Commit 4b76239e authored by Matthieu Schaller's avatar Matthieu Schaller
Browse files

Document how to switch on the distributed snapshots

parent b3f1d443
......@@ -683,7 +683,23 @@ with a base name and output number that matches the snapshot name
(e.g. ``stf_base_name_1234.hdf5``) irrespective of the name specified in the
section dedicated to VELOCIraptor. Note that the invocation of VELOCIraptor at
every dump is done additionally to the stand-alone dumps that can be specified
in the corresponding section of the YAML parameter file.
in the corresponding section of the YAML parameter file. When running with
_more_ calls to VELOCIraptor than snapshots, gaps between snapshot numbers will
be created to accommodate for the intervening VELOCIraptor-only catalogs.
When running over MPI, users have the option to split the snapshot over more
than one file. This can be useful if the parallel-io on a given system is slow
but has the drawback of producing many files per time slice. This is activated
by setting the parameter:
* Distributed snapshots over MPI: ``distributed`` (default: ``0``).
This option has no effect when running the non-MPI version of the code. Note
also that unlike other codes, SWIFT does *not* let the users chose the number of
individual files over which a snapshot is distributed. This is set by the number
of MPI ranks used in a given run. The individual files of snapshot 1234 will
have the name ``base_name_1234.x.hdf5`` where when running on N MPI ranks, ``x``
runs from 0 to N-1.
Users can optionally specify the level of compression used by the HDF5 library
using the parameter:
......@@ -709,7 +725,7 @@ one described above (See the :ref:`Parameters_units` section) and read:
* a unit of electric current ``UnitCurrent_in_cgs`` (default: ``InternalUnitSystem:UnitCurrent_in_cgs``),
* a unit of temperature ``UnitTemp_in_cgs`` (default: ``InternalUnitSystem:UnitTemp_in_cgs``).
When un-specified, these all take the same value as assumed by the internal
When unspecified, these all take the same value as assumed by the internal
system of units. These are rarely used but can offer a practical alternative to
converting data in the post-processing of the simulations.
......@@ -730,11 +746,13 @@ Showing all the parameters for a basic hydro test-case, one would have:
basename: sedov
subdir: snapshots
time_first: 0.01
delta_time: 0.005
invoke_stf: 0
int_time_label_on: 0
compression: 3
distributed: 1
UnitLength_in_cgs: 1. # Use cm in outputs
UnitMass_in_cgs: 1. # Use grams in outputs
UnitVelocity_in_cgs: 1. # Use cm/s in outputs
......@@ -4493,6 +4493,12 @@ void engine_config(int restart, int fof, struct engine *e,
/* Check that the snapshot naming policy is valid */
if (e->snapshot_invoke_stf && e->snapshot_int_time_label_on)
"Cannot use snapshot time labels and VELOCIraptor invocations "
/* Check that we are invoking VELOCIraptor only if we have it */
if (e->snapshot_invoke_stf &&
!(e->policy & engine_policy_structure_finding)) {
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