points arg = yes or no to include a Points section in the file fileper arg = Np Np = write one file for every this many processors nfile arg = Nf Nf = write this many files, one from each of Nf processors
write_surf data.surf write_surf data.surf points no write_surf data.surf.% nfile 50
Write a surface file in text format describing the currently defined surface elements, whether they be explicit or implicit surfaces. See the read_surf and read_isurf commands for a definition of surface elements and how they are defined and used be SPARTA. The surface file can be used for later input to a new simulation or for post-processing and visualization.
Note that if surface objects were clipped when read in by the read_surf command then some surface elements may have been deleted and new ones created. Likewise for the points that define the end points or corner points of surface element lines (2d) or triangles (3d). Similarly, if surface elements have been removed by the remove_surf command, then points may have also been deleted. In either case, surface points and elements are renumbered by these operations to create compressed, contiguous lists. These lists are what is output by this command.
The file is written as a text file in the same format as the read_surf command reads in. Note that a Points section is optional. If the points keyword is specified with a value of yes, then a Points section is included in the file. If the value is no, then point coordinates are included with individual lines or triangles.
Similar to dump files, the surface filename can contain two wild-card characters. If a "*" appears in the filename, it is replaced with the current timestep value. If a "%" character appears in the filename, then one file is written by each processor and the "%" character is replaced with the processor ID from 0 to P-1. An additional file with the "%" replaced by "base" is also written, which contains global information, i.e. just the header information for the number of points and lines or triangles, as described on the read_surf doc page.
For example, the files written for filename data.% would be data.base, data.0, data.1, ..., data.P-1. This creates smaller files and can be a fast mode of output and subsequent input on parallel machines that support parallel I/O. The optional fileper and nfile keywords discussed below can alter the number of files written.
Note that implicit surfaces read in by the read_isurf command can be written out by the write_surf command, e.g. for visualization purposes. But they cannot be read back in to SPARTA via the read_isurf command, because write_surf creates files in an explicit surface format. See the Howto 6.13 section of the manual for a discussion of explicit and implicit surfaces for an explantion of explicit versus implicit surfaces as well as distributed versus non-distributed storage. You cannot mix explicit and implicit surfaces in the same simulation.
The optional nfile or fileper keywords can be used in conjunction with the "%" wildcard character in the specified surface file name. As explained above, the "%" character causes the surface file to be written in pieces, one piece for each of P processors. By default P = the number of processors the simulation is running on. The nfile or fileper keyword can be used to set P to a smaller value, which can be more efficient when running on a large number of processors.
The nfile keyword sets P to the specified Nf value. For example, if Nf = 4, and the simulation is running on 100 processors, 4 files will be written, by processors 0,25,50,75. Each will collect information from itself and the next 24 processors and write it to a surface file.
For the fileper keyword, the specified value of Np means write one file for every Np processors. For example, if Np = 4, every 4th processor (0,4,8,12,etc) will collect information from itself and the next 3 processors and write it to a surface file.
The default is points = yes.