Hi André...
On 09/12/2011 07:20 AM, André Rossi wrote:
Dear Martin Morgan and Martin Maechler...
Here is an example of the computational time when a slot of a S4 class
is of another S4 class and when it is just one object. I'm sending you
the data file.
Thank you!
Best regards,
André Rossi
############################################################
setClass("SupervisedExample",
representation(
attr.value = "ANY",
target.value = "ANY"
))
setClass("StreamBuffer",
representation=representation(
examples = "list", #SupervisedExample
max.length = "integer"
),
prototype=list(
max.length = as.integer(10000)
)
)
b <- new("StreamBuffer")
load("~/Dropbox/dataList2.RData")
For a reproducible example, I guess you have something like
data <- replicate(10000, new("SupervisedExample"))
b@examples <- data #data is a list of SupervisedExample class.
> system.time({for (i in 1:100) b@examples[[1]]@attr.value[1] = 2 })
Yes, this is slow. [[<-,S4 is not as clever as [[<-,list and performs
extra duplication, including those 10,000 S4 objects it contains.
As before, an improvement is to think in terms of vectors, maybe a
'SupervisedExamples' class to act as a collection of examples
setClass("SupervisedExamples",
representation=representation(
attr.value = "list",
target.value = "list"))
setClass("StreamBuffer",
representation=representation(
examples="SupervisedExamples"))
SupervisedExamples <-
function(attr.value=vector("list", n),
target.value=vector("list", n), n, ...)
{
new("SupervisedExamples", attr.value=attr.value,
target.value=target.value, ...)
}
StreamBuffer <-
function(examples, ...)
{
new("StreamBuffer", examples=examples, ...)
}
data <- SupervisedExamples(n=100000)
b <- StreamBuffer(data)
I then have
> system.time({for (i in 1:100) data@attr.value[[1]] = 2 })
user system elapsed
1.081 0.013 1.094
> system.time({for (i in 1:100) b@examples@attr.value[[1]] <- 2})
user system elapsed
4.283 0.000 4.295
(note the 10x increase in size); still slower, but this will be
amortized when the updates are vectorized, e.g.,
> idx = sample(length(b@examples@attr.value), 100)
> system.time(b@examples@attr.value[idx] <- list(2))
user system elapsed
0.013 0.000 0.014
A further change might be to recognize 'StreamBuffer' as an abstract
class that SupervisedExamples extends
setClass("StreamBuffer",
representation=representation(
"VIRTUAL", max.len="integer"),
prototype=prototype(max.len=100000L),
validity=function(object) {
if (obj...@max.len < length(object))
"too many elements"
else TRUE
})
setMethod(length, "StreamBuffer", function(x) {
stop("'length' undefined on '", class(x), "'")
})
setClass("SupervisedExamples",
representation=representation(
attr.value = "list",
target.value = "list"),
contains="StreamBuffer")
setMethod(length, "SupervisedExamples", function(x) {
length(x@attr.value)
})
SupervisedExamples <-
function(attr.value=vector("list", n),
target.value=vector("list", n), n, ...)
{
new("SupervisedExamples", attr.value=attr.value,
target.value=target.value, ...)
}
data <- SupervisedExamples(n=100000)
> system.time({for (i in 1:100) data@attr.value[[1]] = 2 })
user system elapsed
1.043 0.014 1.061
Martin Morgan
user system elapsed
16.837 0.108 18.244
> system.time({for (i in 1:100) data[[1]]@attr.value[1] = 2 })
user system elapsed
0.024 0.000 0.026
############################################################
2011/9/10 Martin Morgan <mtmor...@fhcrc.org <mailto:mtmor...@fhcrc.org>>
On 09/10/2011 08:08 AM, André Rossi wrote:
Hi everybody!
I'm creating an object of a S4 class that has two slots:
ListExamples, which
is a list, and idx, which is an integer (as the code below).
Then, I read a data.frame file with 10000 (ten thousands) of
lines and 10
columns, do some pre-processing and, basically, I store each
line as an
element of a list in the slot ListExamples of the S4 object.
However, many
operations after this take a considerable time.
Can anyone explain me why dois it happen? Is it possible to
speed up an
script that deals with a big number of data (it might be
data.frame or
list)?
Thank you,
André Rossi
setClass("Buffer",
representation=representation(
Listexamples = "list",
idx = "integer"
)
)
Hi André,
Can you provide a simpler and more reproducible example, for instance
> setClass("Buf", representation=representation(__lst="list"))
[1] "Buf"
> b=new("Buf", lst=replicate(10000, list(10), simplify=FALSE))
> system.time({ b@lst[[1]][[1]] = 2 })
user system elapsed
0.005 0.000 0.005
Generally it sounds like you're modeling the rows as elements of
Listofelements, but you're better served by modeling the columns
(lst = replicate(10, integer(10000)), if all of your 10 columns were
integer-valued, for instance). Also, S4 is providing some measure of
type safety, and you're undermining that by having your class
contain a 'list'. I'd go after
setClass("Buffer",
representation=representation(
col1="integer",
col2="character",
col3="numeric"
## etc.
),
validity=function(object) {
nms <- slotNames(object)
len <- sapply(nms, function(nm) length(slot(object, nm)))
if (1L != length(unique(len)))
"slots must all be of same length"
else TRUE
})
Buffer <-
function(col1, col2, col3, ...)
{
new("Buffer", col1=col1, col2=col2, col3=col3, ...)
}
Let's see where the inefficiencies are before deciding that this is
an S4 issue.
Martin
[[alternative HTML version deleted]]
________________________________________________
R-help@r-project.org <mailto:R-help@r-project.org> mailing list
https://stat.ethz.ch/mailman/__listinfo/r-help
<https://stat.ethz.ch/mailman/listinfo/r-help>
PLEASE do read the posting guide
http://www.R-project.org/__posting-guide.html
<http://www.R-project.org/posting-guide.html>
and provide commented, minimal, self-contained, reproducible code.
--
Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109
Location: M1-B861
Telephone: 206 667-2793 <tel:206%20667-2793>
--
Computational Biology
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N. PO Box 19024 Seattle, WA 98109
Location: M1-B861
Telephone: 206 667-2793
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
