R Under development (unstable) (2024-01-23 r85822 ucrt) -- "Unsuffered Consequences"
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> library("R.huge")
R.huge v0.10.1 successfully loaded. See ?R.huge for help.

Attaching package: 'R.huge'

The following objects are masked from 'package:base':

    colnames, flush, isOpen, ncol, nrow, rowMeans, rowSums, rownames

> library("R.utils")
Loading required package: R.oo
Loading required package: R.methodsS3
R.methodsS3 v1.8.2 (2022-06-13 22:00:14 UTC) successfully loaded. See ?R.methodsS3 for help.
R.oo v1.26.0 successfully loaded. See ?R.oo for help.

Attaching package: 'R.oo'

The following object is masked from 'package:R.methodsS3':

    throw

The following objects are masked from 'package:methods':

    getClasses, getMethods

The following objects are masked from 'package:base':

    attach, detach, load, save

R.utils v2.12.3 (2023-11-18 01:00:02 UTC) successfully loaded. See ?R.utils for help.

Attaching package: 'R.utils'

The following object is masked from 'package:utils':

    timestamp

The following objects are masked from 'package:base':

    cat, commandArgs, getOption, isOpen, nullfile, parse, use, warnings

> 
> if ("covr" %in% loadedNamespaces())
+   options("R.utils::onNonSeekable"="warning")
> 
> pathname <- "example.Rmatrix"
> if (isFile(pathname)) {
+   file.remove(pathname)
+   if (isFile(pathname))
+     stop("File not deleted: ", pathname)
+ }
> 
> nrow <- 50000
> ncol <- 20
> X <- FileFloatMatrix(pathname, nrow=nrow, ncol=ncol, byrow=TRUE)
> 
> n <- 1000
> for (ii in 1:(nrow%/%n)) {
+   jj <- ((ii-1)*n+1):(ii*n)
+   tim <- system.time({
+     X[jj,] <- matrix(rnorm(n*ncol), ncol=ncol)
+   })[3]
+   cat(ii, tim, "s\n")
+ }
1 0.01 s
2 0.02 s
3 0.02 s
4 0 s
5 0.01 s
6 0 s
7 0 s
8 0.02 s
9 0 s
10 0.02 s
11 0.02 s
12 0.01 s
13 0 s
14 0 s
15 0 s
16 0 s
17 0.01 s
18 0.01 s
19 0.02 s
20 0.01 s
21 0 s
22 0.01 s
23 0.02 s
24 0 s
25 0.02 s
26 0.02 s
27 0 s
28 0.01 s
29 0.01 s
30 0 s
31 0 s
32 0 s
33 0 s
34 0.02 s
35 0.02 s
36 0 s
37 0.01 s
38 0.01 s
39 0.02 s
40 0 s
41 0 s
42 0.01 s
43 0.01 s
44 0.01 s
45 0 s
46 0.01 s
47 0 s
48 0.02 s
49 0.01 s
50 0.01 s
> 
> set.seed(1)
> for (ii in 1:6) {
+   jj <- sample(1:nrow, size=n)
+   tim <- system.time({
+     y <- X[jj,]
+   })[3]
+   cat(ii, tim, "s\n")
+ }
1 0.11 s
2 0.08 s
3 0.09 s
4 0.11 s
5 0.1 s
6 0.09 s
> 
> close(X)
> delete(X)
> 
> proc.time()
   user  system elapsed 
   3.70    0.26    3.95