[R-SIG-Win] R4.2.3 slower than R4.1.3 on Windows only

[Fredrik Skoog]

Hi,

If you run:

library(microbenchmark)
m <- matrix(rnorm(28000000), nrow=7000, byrow=TRUE)
rownames(m) <- rownames(m, do.NULL = FALSE, prefix = "this is a row name")
colnames(m) <- colnames(m, do.NULL = FALSE, prefix = "this is a column
name")
microbenchmark(df <- as.data.frame(m, keep.rownames=TRUE), times=10)

The results shows worse performance in R4.2.3 (also bigger variations)
compared to v4.1.3. Also v4.2.0 shows worse performance, so it looks like
it's 4.2.0 and later that has this issue. On Linux it's all good, so it
seems to be a Windows only issue.

Version 4.2.3
==============

Run 1
------
Unit: seconds
                                         expr      min       lq     mean
 median       uq      max neval
 df <- as.data.frame(m, keep.rownames = TRUE) 1.324839 2.411304 2.760553
2.593452 3.290228 4.263175    10

Run 2
------
Unit: milliseconds
                                         expr      min     lq     mean
 median       uq     max neval
 dt <- as.data.frame(m, keep.rownames = TRUE) 967.5651 1054.8 1155.453
1149.767 1194.742 1451.14    10


Version 4.1.3
===============

Run 1:
------

Unit: milliseconds
                                         expr      min       lq     mean
 median       uq      max neval
 df <- as.data.frame(m, keep.rownames = TRUE) 274.5478 298.2477 320.3988
320.9164 342.8119 375.6841    10

Run 2:
-------
Unit: milliseconds
                                         expr      min       lq     mean
 median       uq      max neval
 df <- as.data.frame(m, keep.rownames = TRUE) 278.5369 310.0312 313.0745
313.3275 320.0294 343.7539    10

I have tried it on two different machines, with the same result.

-----

The above example is just trying to do something simple that exposes the
issue, but as.data.table behaves similarly. Also it shows huge variations
in time. We had a script that ran in 12 minutes in v3.6.3 and it took 18
min with v4.2.3, with v4.1.3 it takes around 9 minutes.

Has anyone else noticed this? I noticed in the release notes that Doug Leas
malloc was replaced in v4.2.0 and that's a windows only change.

Best regards,

Fredrik

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