add documentation for threads

R/predict.R

@@ -36,6 +36,9 @@
 ##' 
 ##' For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 ##' To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+##' 
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##'
 ##' @title Ranger prediction
 ##' @param object Ranger \code{ranger.forest} object.
@@ -45,7 +48,7 @@
 ##' @param type Type of prediction. One of 'response', 'se', 'terminalNodes', 'quantiles' with default 'response'. See below for details.
 ##' @param se.method Method to compute standard errors. One of 'jack', 'infjack' with default 'infjack'. Only applicable if type = 'se'. See below for details.
 ##' @param seed Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Default is 2 if not set by options/environment variables (see below).
 ##' @param verbose Verbose output on or off.
 ##' @param inbag.counts Number of times the observations are in-bag in the trees.
 ##' @param ... further arguments passed to or from other methods.
@@ -433,6 +436,9 @@ predict.ranger.forest <- function(object, data, predict.all = FALSE,
 ##' 
 ##' For classification and \code{predict.all = TRUE}, a factor levels are returned as numerics.
 ##' To retrieve the corresponding factor levels, use \code{rf$forest$levels}, if \code{rf} is the ranger object.
+##' 
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##'
 ##' @title Ranger prediction
 ##' @param object Ranger \code{ranger} object.
@@ -444,7 +450,7 @@ predict.ranger.forest <- function(object, data, predict.all = FALSE,
 ##' @param quantiles Vector of quantiles for quantile prediction. Set \code{type = 'quantiles'} to use.
 ##' @param what User specified function for quantile prediction used instead of \code{quantile}. Must return numeric vector, see examples.
 ##' @param seed Random seed. Default is \code{NULL}, which generates the seed from \code{R}. Set to \code{0} to ignore the \code{R} seed. The seed is used in case of ties in classification mode.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Default is 2 if not set by options/environment variables (see below).
 ##' @param verbose Verbose output on or off.
 ##' @param ... further arguments passed to or from other methods.
 ##' @return Object of class \code{ranger.prediction} with elements

R/ranger.R

@@ -96,10 +96,10 @@
 ##' To use only the SNPs without sex or other covariates from the phenotype file, use \code{0} on the right hand side of the formula. 
 ##' Note that missing values are treated as an extra category while splitting.
 ##' 
-##' See \url{https://github.com/imbs-hl/ranger} for the development version.
+##' By default, ranger uses 2 threads. The default can be changed with: (1) \code{num.threads} in ranger/predict call, (2) environment variable
+##' R_RANGER_NUM_THREADS, (3) \code{options(ranger.num.threads = N)}, (4) \code{options(Ncpus = N)}, with precedence in that order.
 ##' 
-##' With recent R versions, multithreading on Windows platforms should just work. 
-##' If you compile yourself, the new RTools toolchain is required.
+##' See \url{https://github.com/imbs-hl/ranger} for the development version.
 ##' 
 ##' @title Ranger
 ##' @param formula Object of class \code{formula} or \code{character} describing the model to fit. Interaction terms supported only for numerical variables.
@@ -133,7 +133,7 @@
 ##' @param quantreg Prepare quantile prediction as in quantile regression forests (Meinshausen 2006). Regression only. Set \code{keep.inbag = TRUE} to prepare out-of-bag quantile prediction.
 ##' @param time.interest Time points of interest (survival only). Can be \code{NULL} (default, use all observed time points), a vector of time points or a single number to use as many time points (grid over observed time points).
 ##' @param oob.error Compute OOB prediction error. Set to \code{FALSE} to save computation time, e.g. for large survival forests.
-##' @param num.threads Number of threads. Default is number of CPUs available.
+##' @param num.threads Number of threads. Default is 2 if not set by options/environment variables (see below).
 ##' @param save.memory Use memory saving (but slower) splitting mode. No effect for survival and GWAS data. Warning: This option slows down the tree growing, use only if you encounter memory problems.
 ##' @param verbose Show computation status and estimated runtime.
 ##' @param node.stats Save node statistics. Set to \code{TRUE} to save prediction, number of observations and split statistics for each node.