On 11/15/12 7:53 PM, "Henrik Bengtsson" <hb at biostat.ucsf.edu> wrote:
>Is there any write up/discussion/plans on the various types of
>parallel computations out there:
>
>(1) one machine / multi-core/multi-threaded
>(2) multiple machines / multiple processes
>(3) batch / queue processing (on large compute clusters with many users).
>(4) ...
>
>Are we/you mainly focusing on (1) and (2)?
>
>/Henrik
>
>On Thu, Nov 15, 2012 at 6:21 AM, Kasper Daniel Hansen
><kasperdanielhansen at gmail.com> wrote:
>> I'll second Ryan's patch (at least in principle). When I parallelize
>> across multiple cores, I have always found mc.preschedule to be an
>> important option to expose (that, and the number of cores, is all I
>> use routinely).
>>
>> Kasper
>>
>> On Wed, Nov 14, 2012 at 7:14 PM, Ryan C. Thompson
>><rct at thompsonclan.org> wrote:
>>> I just submitted a pull request. I'll add tests shortly if I can
>>>figure out
>>> how to write them.
>>>
>>>
>>> On Wed 14 Nov 2012 03:50:36 PM PST, Martin Morgan wrote:
>>>>
>>>> On 11/14/2012 03:43 PM, Ryan C. Thompson wrote:
>>>>>
>>>>> Here are two alternative implementations of pvec. pvec2 is just a
>>>>> simple rewrite
>>>>> of pvec to use mclapply. pvec3 then extends pvec2 to accept a
>>>>> specified chunk
>>>>> size or a specified number of chunks. If the number of chunks exceeds
>>>>> the number
>>>>> of cores, then multiple chunks will get run sequentially on each
>>>>> core. pvec3
>>>>> also exposes the "mc.prescheule" argument of mclapply, since that is
>>>>> relevant
>>>>> when there are more chunks than cores. Lastly, I provide a
>>>>> "pvectorize" function
>>>>> which can be called on a regular vectorized function to make it into
>>>>> a pvec'd
>>>>> version of itself. Usage is like: sqrt.parallel <- pvectorize(sqrt);
>>>>> sqrt.parallel(1:1000).
>>>>>
>>>>> pvec2 <- function(v, FUN, ..., mc.set.seed = TRUE, mc.silent = FALSE,
>>>>> mc.cores = getOption("mc.cores", 2L), mc.cleanup =
>>>>> TRUE)
>>>>> {
>>>>> env <- parent.frame()
>>>>> cores <- as.integer(mc.cores)
>>>>> if(cores < 1L) stop("'mc.cores' must be >= 1")
>>>>> if(cores == 1L) return(FUN(v, ...))
>>>>>
>>>>> if(mc.set.seed) mc.reset.stream()
>>>>>
>>>>> n <- length(v)
>>>>> si <- splitIndices(n, cores)
>>>>> res <- do.call(c,
>>>>> mclapply(si, function(i) FUN(v[i], ...),
>>>>> mc.set.seed=mc.set.seed,
>>>>> mc.silent=mc.silent,
>>>>> mc.cores=mc.cores,
>>>>> mc.cleanup=mc.cleanup))
>>>>> if (length(res) != n)
>>>>> warning("some results may be missing, folded or caused an
>>>>>error")
>>>>> res
>>>>> }
>>>>> pvec3 <- function(v, FUN, ..., mc.set.seed = TRUE, mc.silent = FALSE,
>>>>> mc.cores = getOption("mc.cores", 2L), mc.cleanup =
>>>>> TRUE,
>>>>> mc.preschedule=FALSE, num.chunks, chunk.size)
>>>>> {
>>>>> env <- parent.frame()
>>>>> cores <- as.integer(mc.cores)
>>>>> if(cores < 1L) stop("'mc.cores' must be >= 1")
>>>>> if(cores == 1L) return(FUN(v, ...))
>>>>>
>>>>> if(mc.set.seed) mc.reset.stream()
>>>>>
>>>>> n <- length(v)
>>>>> if (missing(num.chunks)) {
>>>>> if (missing(chunk.size)) {
>>>>> num.chunks <- cores
>>>>> } else {
>>>>> num.chunks <- ceiling(n/chunk.size)
>>>>> }
>>>>> }
>>>>> si <- splitIndices(n, num.chunks)
>>>>> res <- do.call(c,
>>>>> mclapply(si, function(i) FUN(v[i], ...),
>>>>> mc.set.seed=mc.set.seed,
>>>>> mc.silent=mc.silent,
>>>>> mc.cores=mc.cores,
>>>>> mc.cleanup=mc.cleanup,
>>>>> mc.preschedule=mc.preschedule))
>>>>> if (length(res) != n)
>>>>> warning("some results may be missing, folded or caused an
>>>>>error")
>>>>> res
>>>>> }
>>>>>
>>>>> pvectorize <- function(FUN) {
>>>>> function(...) pvec3(FUN=FUN, ...)
>>>>> }
>>>>
>>>>
>>>> would be great to have these as 'pull' requests in github; pvec3 as a
>>>> replacement for pvec, if it's implementing the same concept but
>>>>better.
>>>>
>>>> Unit tests would be good (yes being a little hypocritical).
>>>> inst/unitTests, using RUnit, examples in
>>>>
>>>>
>>>>
>>>>https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/IRanges/ins
>>>>t/unitTests
>>>>
>>>>
>>>> with username / password readonly
>>>>
>>>> Martin
>>>>
>>>>> On Wed 14 Nov 2012 02:23:30 PM PST, Michael Lawrence wrote:
>>>>>>
>>>>>>
>>>>>> On Wed, Nov 14, 2012 at 12:23 PM, Martin Morgan <mtmorgan at fhcrc.org>
>>>>>> wrote:
>>>>>>
>>>>>>>
>>>>>>> Interested developers -- I added the start of a BiocParallel
>>>>>>> package to
>>>>>>> the Bioconductor subversion repository and build system.
>>>>>>>
>>>>>>> The package is mirrored on github to allow for social coding; I
>>>>>>> encourage
>>>>>>> people to contribute via that mechanism.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>https://github.com/**Bioconductor/BiocParallel<https://github.com/Bi
>>>>>>>oconductor/BiocParallel>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> The purpose is to help focus our efforts at developing appropriate
>>>>>>> parallel paradigms. Currently the package Imports: parallel and
>>>>>>> implements
>>>>>>> pvec and mclapply in a way that allows for operation on any vector
>>>>>>> or list
>>>>>>> supporting length(), [, and [[ (the latter for mclapply). pvec in
>>>>>>> particular seems to be appropriate for GRanges-like objects, where
>>>>>>> we don't
>>>>>>> necessarily want to extract many thousands of S4 instances of
>>>>>>> individual
>>>>>>> ranges with [[.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> Makes sense. Besides, [[ does not even work on GRanges. One
>>>>>> limitation of
>>>>>> pvec is that it does not support a chunk size; it just uses
>>>>>>length(x) /
>>>>>> ncores. It would be nice to be able to restrict that, which would
>>>>>>then
>>>>>> require multiple jobs per core. Unless I'm missing something.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Hopefully the ideas in the package can be folded back in to
>>>>>>> parallel as
>>>>>>> they mature.
>>>>>>>
>>>>>>> Martin
>>>>>>> --
>>>>>>> Dr. Martin Morgan, PhD
>>>>>>> Fred Hutchinson Cancer Research Center
>>>>>>> 1100 Fairview Ave. N.
>>>>>>> PO Box 19024 Seattle, WA 98109
>>>>>>>
>>>>>>> ______________________________**_________________
>>>>>>> Bioc-devel at r-project.org mailing list
>>>>>>>
>>>>>>>
>>>>>>>https://stat.ethz.ch/mailman/**listinfo/bioc-devel<https://stat.ethz
>>>>>>>.ch/mailman/listinfo/bioc-devel>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> [[alternative HTML version deleted]]
>>>>>>
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