bploop {BiocParallel} | R Documentation

## Internal Functions for SNOW-style Parallel Evaluation

### Description

The functions documented on this page are primarily for use within BiocParallel to enable SNOW-style parallel evaluation, using communication between manager and worker nodes through sockets.

### Usage

    ## S3 method for class 'lapply'
    bploop(manager, X, FUN, ARGS, BPPARAM, ...)

    ## S3 method for class 'iterate'
    bploop(manager, ITER, FUN, ARGS, BPPARAM,
           REDUCE, init, reduce.in.order, progress.length, ...)

### Arguments

`manager` | An object representing the manager node. For workers, this is the node to which the worker will communicate. For managers, this is the form of iteration – `lapply` or `iterate`.
`X` | A vector of jobs to be performed.
`FUN` | A function to apply to each job.
`ARGS` | A list of arguments to be passed to `FUN`.
`BPPARAM` | An instance of a `BiocParallelParam` class.
`ITER` | A function used to generate jobs. No more jobs are available when `ITER()` returns `NULL`.
`REDUCE` | (Optional) A function combining two values returned by `FUN` into a single value.
`init` | (Optional) Initial value for reduction.
`reduce.in.order` | (Optional) logical(1) indicating that reduction must occur in the order jobs are dispatched (`TRUE`) or that reduction can occur in the order jobs are completed (`FALSE`).
`...` | Additional arguments, ignored in all cases.
`progress.length` | (Optional) The length of the progress bar. Used by `bploop.lapply` to indicate use of a progress bar rather than iterator.

### Details

Workers enter a loop. They wait to receive a message (R list) from the `manager`. The message contains a `type` element, with evaluation as follows:

“EXEC”

  Execute the R code in the message, returning the result to the `manager`.

“DONE”

  Signal termination to the `manager`, terminate the worker.

Managers under `lapply` dispatch pre-determined jobs, `X`, to workers, collecting the results from and dispatching new jobs to the first available worker. The manager returns a list of results, in a one-to-one correspondence with the order of jobs supplied, when all jobs have been evaluated.

Managers under `iterate` dispatch an undetermined number of jobs to workers, collecting previous jobs from and dispatching new jobs to the first available worker. Dispatch continues until available jobs are exhausted. The return value is by default a list of results in a one-to-one correspondence with the order of jobs supplied. The return value is influenced by `REDUCE`, `init`, and `reduce.in.order`.

### Author(s)

Valerie Obenchain, Martin Morgan. Derived from similar functionality in the snow and parallel packages.

### Examples

    ## These functions are not meant to be called by the end user.

[Package BiocParallel version 1.28.3 Index]