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Dynamic-within-static branching for data frames (count batching).

Source: R/tar_map2_count.R, R/tar_map2_count_raw.R
tar_map2_count.Rd

Define targets for batched dynamic-within-static branching for data frames, where the user sets the (maximum) number of batches.

tar_map2_count() expects unevaluated language for arguments name, command1, command2, columns1, and columns2. tar_map2_count_raw() expects a character string for name and an evaluated expression object for each of command1, command2, columns1, and columns2.

Usage

tar_map2_count(
  name,
  command1,
  command2,
  values = NULL,
  names = NULL,
  descriptions = tidyselect::everything(),
  batches = 1L,
  combine = TRUE,
  suffix1 = "1",
  suffix2 = "2",
  columns1 = tidyselect::everything(),
  columns2 = tidyselect::everything(),
  rep_workers = 1,
  delimiter = "_",
  unlist = FALSE,
  tidy_eval = targets::tar_option_get("tidy_eval"),
  packages = targets::tar_option_get("packages"),
  library = targets::tar_option_get("library"),
  format = targets::tar_option_get("format"),
  repository = targets::tar_option_get("repository"),
  error = targets::tar_option_get("error"),
  memory = targets::tar_option_get("memory"),
  garbage_collection = targets::tar_option_get("garbage_collection"),
  deployment = targets::tar_option_get("deployment"),
  priority = targets::tar_option_get("priority"),
  resources = targets::tar_option_get("resources"),
  storage = targets::tar_option_get("storage"),
  retrieval = targets::tar_option_get("retrieval"),
  cue = targets::tar_option_get("cue"),
  description = targets::tar_option_get("description")
)

tar_map2_count_raw(
  name,
  command1,
  command2,
  values = NULL,
  names = NULL,
  descriptions = quote(tidyselect::everything()),
  batches = 1L,
  combine = TRUE,
  suffix1 = "1",
  suffix2 = "2",
  columns1 = quote(tidyselect::everything()),
  columns2 = quote(tidyselect::everything()),
  rep_workers = 1,
  delimiter = "_",
  unlist = FALSE,
  tidy_eval = targets::tar_option_get("tidy_eval"),
  packages = targets::tar_option_get("packages"),
  library = targets::tar_option_get("library"),
  format = targets::tar_option_get("format"),
  repository = targets::tar_option_get("repository"),
  error = targets::tar_option_get("error"),
  memory = targets::tar_option_get("memory"),
  garbage_collection = targets::tar_option_get("garbage_collection"),
  deployment = targets::tar_option_get("deployment"),
  priority = targets::tar_option_get("priority"),
  resources = targets::tar_option_get("resources"),
  storage = targets::tar_option_get("storage"),
  retrieval = targets::tar_option_get("retrieval"),
  cue = targets::tar_option_get("cue"),
  description = targets::tar_option_get("description")
)

Arguments

name

Name of the target. tar_rep() expects unevaluated name and command arguments (e.g. tar_rep(name = sim, command = simulate())) whereas tar_rep_raw() expects an evaluated string for name and an evaluated expression object for command (e.g. tar_rep_raw(name = "sim", command = quote(simulate()))).

command1

R code to create named arguments to command2. Must return a data frame with one row per call to command2 when run.

In regular tarchetypes functions, the command1 argument is an unevaluated expression. In the "_raw" versions of functions, command1 is an evaluated expression object.

command2

R code to map over the data frame of arguments produced by command1. Must return a data frame.

In regular tarchetypes functions, the command2 argument is an unevaluated expression. In the "_raw" versions of functions, command2 is an evaluated expression object.

values

Named list or data frame with values to iterate over. The names are the names of symbols in the commands and pattern statements, and the elements are values that get substituted in place of those symbols. tar_map() uses these elements to create new R code, so they should be basic types, symbols, or R expressions. For objects even a little bit complicated, especially objects with attributes, it is not obvious how to convert the object into code that generates it. For complicated objects, consider using quote() when you define values, as shown at https://github.com/ropensci/tarchetypes/discussions/105.

names

Subset of names(values) used to generate the suffixes in the names of the new targets. The value of names should be a tidyselect expression such as a call to any_of() or starts_with().

descriptions

Names of a column in values to append to the custom description of each generated target. The value of descriptions should be a tidyselect expression such as a call to any_of() or starts_with().

batches

Positive integer of length 1, maximum number of batches (dynamic branches within static branches) of the downstream (command2) targets. Batches are formed from row groups of the command1 target output.

combine

Logical of length 1, whether to create additional downstream targets to combine the results of static branches. The values argument must not be NULL for this combining to take effect. If combine is TRUE and values is not NULL, then separate targets aggregate all dynamic branches within each static branch, and then a final target combines all the static branches together.

suffix1

Character of length 1, suffix to apply to the command1 targets to distinguish them from the command2 targets.

suffix2

Character of length 1, suffix to apply to the command2 targets to distinguish them from the command1 targets.

columns1

A tidyselect expression to select which columns of values to append to the output of all targets. Columns already in the target output are not appended.

In regular tarchetypes functions, the columns1 argument is an unevaluated expression. In the "_raw" versions of functions, columns1 is an evaluated expression object.

columns2

A tidyselect expression to select which columns of command1 output to append to command2 output. Columns already in the target output are not appended. columns1 takes precedence over columns2.

In regular tarchetypes functions, the columns2 argument is an unevaluated expression. In the "_raw" versions of functions, columns2 is an evaluated expression object.

rep_workers

Positive integer of length 1, number of local R processes to use to run reps within batches in parallel. If 1, then reps are run sequentially within each batch. If greater than 1, then reps within batch are run in parallel using a PSOCK cluster.

delimiter

Character of length 1, string to insert between other strings when creating names of targets.

unlist

Logical, whether to flatten the returned list of targets. If unlist = FALSE, the list is nested and sub-lists are named and grouped by the original input targets. If unlist = TRUE, the return value is a flat list of targets named by the new target names.

tidy_eval

Whether to invoke tidy evaluation (e.g. the !! operator from rlang) as soon as the target is defined (before tar_make()). Applies to the command argument.

packages

Character vector of packages to load right before the target runs or the output data is reloaded for downstream targets. Use tar_option_set() to set packages globally for all subsequent targets you define.

library

Character vector of library paths to try when loading packages.

format

Optional storage format for the target's return value. With the exception of format = "file", each target gets a file in _targets/objects, and each format is a different way to save and load this file. See the "Storage formats" section for a detailed list of possible data storage formats.

repository

Character of length 1, remote repository for target storage. Choices:

Note: if repository is not "local" and format is "file" then the target should create a single output file. That output file is uploaded to the cloud and tracked for changes where it exists in the cloud. As of targets version 1.11.0 and higher, the local file is no longer deleted after the target runs.

error

Character of length 1, what to do if the target stops and throws an error. Options:

  • "stop": the whole pipeline stops and throws an error.

  • "continue": the whole pipeline keeps going.

  • "null": The errored target continues and returns NULL. The data hash is deliberately wrong so the target is not up to date for the next run of the pipeline. In addition, as of targets version 1.8.0.9011, a value of NULL is given to upstream dependencies with error = "null" if loading fails.

  • "abridge": any currently running targets keep running, but no new targets launch after that.

  • "trim": all currently running targets stay running. A queued target is allowed to start if:

    1. It is not downstream of the error, and

    2. It is not a sibling branch from the same tar_target() call (if the error happened in a dynamic branch).

    The idea is to avoid starting any new work that the immediate error impacts. error = "trim" is just like error = "abridge", but it allows potentially healthy regions of the dependency graph to begin running. (Visit https://books.ropensci.org/targets/debugging.html to learn how to debug targets using saved workspaces.)

memory

Character of length 1, memory strategy. Possible values:

  • "auto" (default): equivalent to memory = "transient" in almost all cases. But to avoid superfluous reads from disk, memory = "auto" is equivalent to memory = "persistent" for for non-dynamically-branched targets that other targets dynamically branch over. For example: if your pipeline has tar_target(name = y, command = x, pattern = map(x)), then tar_target(name = x, command = f(), memory = "auto") will use persistent memory for x in order to avoid rereading all of x for every branch of y.

  • "transient": the target gets unloaded after every new target completes. Either way, the target gets automatically loaded into memory whenever another target needs the value.

  • "persistent": the target stays in memory until the end of the pipeline (unless storage is "worker", in which case targets unloads the value from memory right after storing it in order to avoid sending copious data over a network).

For cloud-based file targets (e.g. format = "file" with repository = "aws"), the memory option applies to the temporary local copy of the file: "persistent" means it remains until the end of the pipeline and is then deleted, and "transient" means it gets deleted as soon as possible. The former conserves bandwidth, and the latter conserves local storage.

garbage_collection

Logical: TRUE to run base::gc() just before the target runs, in whatever R process it is about to run (which could be a parallel worker). FALSE to omit garbage collection. Numeric values get converted to FALSE. The garbage_collection option in tar_option_set() is independent of the argument of the same name in tar_target().

deployment

Character of length 1. If deployment is "main", then the target will run on the central controlling R process. Otherwise, if deployment is "worker" and you set up the pipeline with distributed/parallel computing, then the target runs on a parallel worker. For more on distributed/parallel computing in targets, please visit https://books.ropensci.org/targets/crew.html.

priority

Deprecated on 2025-04-08 (targets version 1.10.1.9013). targets has moved to a more efficient scheduling algorithm (https://github.com/ropensci/targets/issues/1458) which cannot support priorities. The priority argument of tar_target() no longer has a reliable effect on execution order.

resources

Object returned by tar_resources() with optional settings for high-performance computing functionality, alternative data storage formats, and other optional capabilities of targets. See tar_resources() for details.

storage

Character string to control when the output of the target is saved to storage. Only relevant when using targets with parallel workers (https://books.ropensci.org/targets/crew.html). Must be one of the following values:

  • "worker" (default): the worker saves/uploads the value.

  • "main": the target's return value is sent back to the host machine and saved/uploaded locally.

  • "none": targets makes no attempt to save the result of the target to storage in the location where targets expects it to be. Saving to storage is the responsibility of the user. Use with caution.

retrieval

Character string to control when the current target loads its dependencies into memory before running. (Here, a "dependency" is another target upstream that the current one depends on.) Only relevant when using targets with parallel workers (https://books.ropensci.org/targets/crew.html). Must be one of the following values:

  • "auto" (default): equivalent to retrieval = "worker" in almost all cases. But to avoid unnecessary reads from disk, retrieval = "auto" is equivalent to retrieval = "main" for dynamic branches that branch over non-dynamic targets. For example: if your pipeline has tar_target(x, command = f()), then tar_target(y, command = x, pattern = map(x), retrieval = "auto") will use "main" retrieval in order to avoid rereading all of x for every branch of y.

  • "worker": the worker loads the target's dependencies.

  • "main": the target's dependencies are loaded on the host machine and sent to the worker before the target runs.

  • "none": targets makes no attempt to load its dependencies. With retrieval = "none", loading dependencies is the responsibility of the user. Use with caution.

cue

An optional object from tar_cue() to customize the rules that decide whether the target is up to date.

description

Character of length 1, a custom free-form human-readable text description of the target. Descriptions appear as target labels in functions like tar_manifest() and tar_visnetwork(), and they let you select subsets of targets for the names argument of functions like tar_make(). For example, tar_manifest(names = tar_described_as(starts_with("survival model"))) lists all the targets whose descriptions start with the character string "survival model".

Value

A list of new target definition objects. See the "Target definition objects" section for background.

Details

Static branching creates one pair of targets for each row in values. In each pair, there is an upstream non-dynamic target that runs command1 and a downstream dynamic target that runs command2. command1 produces a data frame of arguments to command2, and command2 dynamically maps over these arguments in batches.

Target definition objects

Most tarchetypes functions are target factories, which means they return target definition objects or lists of target definition objects. target definition objects represent skippable steps of the analysis pipeline as described at https://books.ropensci.org/targets/. Please read the walkthrough at https://books.ropensci.org/targets/walkthrough.html to understand the role of target definition objects in analysis pipelines.

For developers, https://wlandau.github.io/targetopia/contributing.html#target-factories explains target factories (functions like this one which generate targets) and the design specification at https://books.ropensci.org/targets-design/ details the structure and composition of target definition objects.

Replicate-specific seeds

In ordinary pipelines, each target has its own unique deterministic pseudo-random number generator seed derived from its target name. In batched replicate, however, each batch is a target with multiple replicate within that batch. That is why tar_rep() and friends give each replicate its own unique seed. Each replicate-specific seed is created based on the dynamic parent target name, tar_option_get("seed") (for targets version 0.13.5.9000 and above), batch index, and rep-within-batch index. The seed is set just before the replicate runs. Replicate-specific seeds are invariant to batching structure. In other words, tar_rep(name = x, command = rnorm(1), batches = 100, reps = 1, ...) produces the same numerical output as tar_rep(name = x, command = rnorm(1), batches = 10, reps = 10, ...) (but with different batch names). Other target factories with this seed scheme are tar_rep2(), tar_map_rep(), tar_map2_count(), tar_map2_size(), and tar_render_rep(). For the tar_map2_*() functions, it is possible to manually supply your own seeds through the command1 argument and then invoke them in your custom code for command2 (set.seed(), withr::with_seed, or withr::local_seed()). For tar_render_rep(), custom seeds can be supplied to the params argument and then invoked in the individual R Markdown reports. Likewise with tar_quarto_rep() and the execute_params argument.

See also

Other branching: tar_map2(), tar_map2_size(), tar_map_rep(), tar_rep(), tar_rep2(), tar_rep_map(), tar_rep_map_raw()

Examples

if (identical(Sys.getenv("TAR_LONG_EXAMPLES"), "true")) {
targets::tar_dir({ # tar_dir() runs code from a temporary directory.
targets::tar_script({
  tarchetypes::tar_map2_count(
    x,
    command1 = tibble::tibble(
      arg1 = arg1,
      arg2 = seq_len(6)
     ),
    command2 = tibble::tibble(
      result = paste(arg1, arg2),
      random = sample.int(1e9, size = 1),
      length_input = length(arg1)
    ),
    values = tibble::tibble(arg1 = letters[seq_len(2)]),
    batches = 3
   )
})
targets::tar_make()
targets::tar_read(x)
# With tar_map2_count_raw():
targets::tar_script({
  tarchetypes::tar_map2_count_raw(
    name = "x",
    command1 = quote(
      tibble::tibble(
        arg1 = arg1,
        arg2 = seq_len(6)
      )
    ),
    command2 = quote(
      tibble::tibble(
        result = paste(arg1, arg2),
        random = sample.int(1e9, size = 1),
        length_input = length(arg1)
      )
    ),
    values = tibble::tibble(arg1 = letters[seq_len(2)]),
    batches = 3
   )
})
})
}