Options
terraOptions.RdGet or set general options.
Details
The following options are available.
memfrac - value between 0 and 0.9 (larger values give a warning). The fraction of RAM that may be used by the program.
memmin - if memory required is below this threshold (in GB), the memory is assumed to be available. Otherwise, terra checks if it is available.
memmax - the maximum amount of RAM (in GB) that terra is allowed to use when processing a raster dataset. Should be less than what is detected (see mem_info), and higher values are ignored. Set it to a negative number or NA to not set this option. terraOptions only shows the value of memmax if it is set.
tempdir - directory where temporary files are written. The default what is returned by tempdir().
datatype - default data type. See writeRaster.
todisk - logical. If TRUE write all raster data to disk (temp file if no file name is specified). For debugging.
progress - non-negative integer. A progress bar is shown if the number of chunks in which the data is processed is larger than this number. No progress bar is shown if the value is zero.
verbose - logical. If TRUE debugging info is printed for some functions.
tolerance - numeric. Difference in raster extent (expressed as the fraction of the raster resolution) that can be ignored when comparing alignment of rasters.
parallel - logical. The master switch for terra's internal parallelism. When TRUE (the default in version >= 1.9-21), the C++ kernels that have been parallelized with Intel TBB (parts of arith, distance calculations on SpatVector, the fast focal path, etc.) will use multiple threads. When FALSE, all such kernels run on a single thread. Use terra:::.have_TBB() to check whether TBB support was compiled in; without TBB, this option has no effect. The same option can be set per call as a write option, e.g. focal(r, w=21, fun="mean", wopt=list(parallel=TRUE)).
threads - non-negative integer. Cap on the number of threads used by parallel kernels (when parallel=TRUE) and by GDAL warp (in project, resample, warp). 0 (the default) means "no cap": TBB picks a sensible default (usually all logical CPUs) and GDAL uses NUM_THREADS=ALL_CPUS. A positive value caps both at that count, which is useful to leave room for other processes or to keep forked workers from each spawning hundreds of children. The value is honoured by every TBB-parallel kernel in terra through a single tbb::task_arena, and is forwarded to GDAL warp's NUM_THREADS option.
Note
It is possible to set your own default options in "etc/.Rprofile.site" of your R installation like this
options(terra_default=list(tempdir="d:/temp", memfrac=.4))
But that may not be a good practice. It is clearer to set your favorite options at the beginning of each script.
Examples
terraOptions()
#> memfrac : 0.5
#> tolerance : 0.1
#> parallel : TRUE
#> verbose : FALSE
#> memmax : 16
#> todisk : FALSE
#> threads : 0
#> tempdir : /tmp/RtmpjMEXw3
#> datatype : FLT4S
#> memmin : 1
#> progress : 3
terraOptions(memfrac=0.5, tempdir = "c:/temp")
#> Warning: [options] you cannot set the tempdir to a path that does not exist
terraOptions(progress=10)
terraOptions(parallel=TRUE, threads=4) # use TBB, capped at 4 threads
terraOptions()
#> memfrac : 0.5
#> tolerance : 0.1
#> parallel : TRUE
#> verbose : FALSE
#> memmax : 16
#> todisk : FALSE
#> threads : 4
#> tempdir : /tmp/RtmpjMEXw3
#> datatype : FLT4S
#> memmin : 1
#> progress : 10