16.51. parallel_sfs

The program parallel_sfs is a wrapper around sfs (Section 16.67) meant to divide the input DEM into tiles with overlap, run sfs on each tile as multiple processes, potentially on multiple machines, and then merge the results into a single output DEM. It has the same options as sfs, and a few additional ones, as outlined below.

An example for how to invoke this program is in Section 11.10.11. See Section 11.1 for the larger context.

If having many computing nodes, the option --nodes-list must be set, to ensure all nodes are used.

Usage:

parallel_sfs -i <input DEM> -n <max iterations> -o <output prefix> \
  <images> [other options]

Command-line options for parallel_sfs:

--tile-size <integer (default: 300)>

Size of approximately square tiles to break up processing into (not counting the padding).

--padding <integer (default: 50)>

How much to expand a tile in each direction. This helps with reducing artifacts in the final mosaicked SfS output.

--processes <integer>

Number of processes to use on each node (the default is for the program to choose).

--num-processes <integer>

Same as --processes. Used for backwards compatibility.

--nodes-list <filename>

A file containing the list of computing nodes, one per line. If not provided, run on the local machine. See also Section 8.16.

--threads <integer (default: 8)>

How many threads each process should use. This will be changed to 1 for ISIS cameras when --use-approx-camera-models is not set (Section 16.67), as ISIS is single-threaded. Not all parts of the computation benefit from parallelization.

--prep-step <string (default: None)>

Run parallel_sfs twice, before mosaicking the final results. First time add these options to the sfs program (after estimating the initial exposures). Second time add the options in --main-step. Must use this as --prep-step="options". Without the equal sign it will fail to parse the options because of limitations of the Python argparse module. See an example in Section 11.12.

--main-step <string (default: None)>

See: --prep-step.

--parallel-options <string (default: “–sshdelay 0.2”)>

Options to pass directly to GNU Parallel.

--resume

Resume a partially done run. Only process the tiles for which the desired per-tile output files are missing or invalid (as checked by gdalinfo).

--suppress-output

Suppress output of sub-calls.

-v, --version

Display the version of software.

-h, --help

Display the help message.