I just got a new Windows laptop (i7, 10th generation CPU), installed
'Windows Subsystem for Linux 2' and then installed Ubuntu 20.04 and
used 'apt-get install' to install packages that the R build seems
to require. In particular, I am using gcc version 9.3.0. The
build went without a hitch but the tests showed that deparse(1e-16)
produced "1.00000000000000e-16" instead of the expected
"1e-16".
It looks like the problem is in src/main/format.c:scientific(). The
lowest two+ bytes in the fractional part of the long double (80-bit)
return value of powl(10.0L, -30L), seem to be corrupted. I made a
standalong program to test powl and saw no problem - it gives the
same results for the fractional part as bc does.
bc: A2425FF7 5E14FC31 A125...
standalone: 22425FF7 5E14FC32
R: 22425FF7 5E151800
There are lots of other small numbers with the same problem:
> grep(value=TRUE, "0e",
vapply((1+(0:10000)/1000)*1e-15, deparse, ""))
[1] "8.56000000000000e-15" "8.71700000000000e-15"
"8.77800000000000e-15"
[4] "8.93500000000000e-15" "9.50800000000000e-15"
"9.83800000000000e-15"
[7] "9.89900000000000e-15" "9.93400000000000e-15"
"9.99500000000000e-15"> str(grep(value=TRUE, "0e", vapply((1+(0:10000)/1000)*1e-14,
deparse, "")))
chr [1:295] "8.00200000000000e-14" "8.00500000000000e-14"
...
Has anyone else seen this? I am wondering if this is an oddity in WSL2
or Ubuntu's gcc-9.3.0.
-Bill
[[alternative HTML version deleted]]
Dirk Eddelbuettel
2020-Nov-17 21:32 UTC
[Rd] formatting issue with gcc 9.3.0 on Ubuntu on WSL2
On 17 November 2020 at 12:34, Bill Dunlap wrote: | I just got a new Windows laptop (i7, 10th generation CPU), installed | 'Windows Subsystem for Linux 2' and then installed Ubuntu 20.04 and | used 'apt-get install' to install packages that the R build seems | to require. In particular, I am using gcc version 9.3.0. The | build went without a hitch but the tests showed that deparse(1e-16) | produced "1.00000000000000e-16" instead of the expected "1e-16". | | It looks like the problem is in src/main/format.c:scientific(). The | lowest two+ bytes in the fractional part of the long double (80-bit) | return value of powl(10.0L, -30L), seem to be corrupted. I made a | standalong program to test powl and saw no problem - it gives the | same results for the fractional part as bc does. | | bc: A2425FF7 5E14FC31 A125... | standalone: 22425FF7 5E14FC32 | R: 22425FF7 5E151800 | | There are lots of other small numbers with the same problem: | | | > grep(value=TRUE, "0e", | vapply((1+(0:10000)/1000)*1e-15, deparse, "")) | [1] "8.56000000000000e-15" "8.71700000000000e-15" "8.77800000000000e-15" | [4] "8.93500000000000e-15" "9.50800000000000e-15" "9.83800000000000e-15" | [7] "9.89900000000000e-15" "9.93400000000000e-15" "9.99500000000000e-15" | > str(grep(value=TRUE, "0e", vapply((1+(0:10000)/1000)*1e-14, deparse, ""))) | chr [1:295] "8.00200000000000e-14" "8.00500000000000e-14" ... | | Has anyone else seen this? I am wondering if this is an oddity in WSL2 | | or Ubuntu's gcc-9.3.0. Plain Ubuntu 20.04.1 here, current. No issue: > str(grep(value=TRUE, "0e", vapply((1+(0:10000)/1000)*1e-14, deparse, ""))) chr(0) > I made sure to start R as `R --vanilla` to not have anything in my dotfiles affect printing. Dirk -- https://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
Tomas Kalibera
2020-Nov-18 09:25 UTC
[Rd] formatting issue with gcc 9.3.0 on Ubuntu on WSL2
On 11/17/20 9:34 PM, Bill Dunlap wrote:> I just got a new Windows laptop (i7, 10th generation CPU), installed > 'Windows Subsystem for Linux 2' and then installed Ubuntu 20.04 and > used 'apt-get install' to install packages that the R build seems > to require. In particular, I am using gcc version 9.3.0. The > build went without a hitch but the tests showed that deparse(1e-16) > produced "1.00000000000000e-16" instead of the expected "1e-16". > > It looks like the problem is in src/main/format.c:scientific(). The > lowest two+ bytes in the fractional part of the long double (80-bit) > return value of powl(10.0L, -30L), seem to be corrupted. I made a > standalong program to test powl and saw no problem - it gives the > same results for the fractional part as bc does. > > bc: A2425FF7 5E14FC31 A125... > standalone: 22425FF7 5E14FC32 > R: 22425FF7 5E151800 > > There are lots of other small numbers with the same problem: > > > > grep(value=TRUE, "0e", > vapply((1+(0:10000)/1000)*1e-15, deparse, "")) > [1] "8.56000000000000e-15" "8.71700000000000e-15" "8.77800000000000e-15" > [4] "8.93500000000000e-15" "9.50800000000000e-15" "9.83800000000000e-15" > [7] "9.89900000000000e-15" "9.93400000000000e-15" "9.99500000000000e-15" >> str(grep(value=TRUE, "0e", vapply((1+(0:10000)/1000)*1e-14, deparse, ""))) > chr [1:295] "8.00200000000000e-14" "8.00500000000000e-14" ... > > Has anyone else seen this? I am wondering if this is an oddity in WSL2 > > or Ubuntu's gcc-9.3.0.Almost surely it is Windows/WSL related, I'm not seeing this on Ubuntu 20.04. One thing to check might be the FPU control word. In a Windows build, R will set as it is on Unix, to use all 80 bits when values stay in FPU registers, which is not the Windows default. This should not matter with SSE anymore, but maybe something is still using the FPU. This is just using inline assembly, so one could enable it as experiment. In principle, this could be also due to some other things specific to Windows that R works around in Windows builds, but doesn't in Linux builds assuming they will not run on Windows. Other issues I had with WSL in the past (trying to build R and run checks) included time-zones and surprising encodings, but I didn't check recently. I would not use R on WSL unless my goal was to diagnose these issues and see if they could be overcome on the R side. Best Tomas> > > > > -Bill > > [[alternative HTML version deleted]] > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel
On Wed, 18 Nov 2020 at 10:26, Tomas Kalibera <tomas.kalibera at gmail.com> wrote:> > On 11/17/20 9:34 PM, Bill Dunlap wrote: > > I just got a new Windows laptop (i7, 10th generation CPU), installed > > 'Windows Subsystem for Linux 2' and then installed Ubuntu 20.04 and > > used 'apt-get install' to install packages that the R build seems > > to require. In particular, I am using gcc version 9.3.0. The > > build went without a hitch but the tests showed that deparse(1e-16) > > produced "1.00000000000000e-16" instead of the expected "1e-16". > > > > It looks like the problem is in src/main/format.c:scientific(). The > > lowest two+ bytes in the fractional part of the long double (80-bit) > > return value of powl(10.0L, -30L), seem to be corrupted. I made a > > standalong program to test powl and saw no problem - it gives the > > same results for the fractional part as bc does. > > > > bc: A2425FF7 5E14FC31 A125... > > standalone: 22425FF7 5E14FC32 > > R: 22425FF7 5E151800 > > > > There are lots of other small numbers with the same problem: > > > > > > > grep(value=TRUE, "0e", > > vapply((1+(0:10000)/1000)*1e-15, deparse, "")) > > [1] "8.56000000000000e-15" "8.71700000000000e-15" "8.77800000000000e-15" > > [4] "8.93500000000000e-15" "9.50800000000000e-15" "9.83800000000000e-15" > > [7] "9.89900000000000e-15" "9.93400000000000e-15" "9.99500000000000e-15" > >> str(grep(value=TRUE, "0e", vapply((1+(0:10000)/1000)*1e-14, deparse, ""))) > > chr [1:295] "8.00200000000000e-14" "8.00500000000000e-14" ... > > > > Has anyone else seen this? I am wondering if this is an oddity in WSL2 > > > > or Ubuntu's gcc-9.3.0.I cannot reproduce this issue (version 20H2, build 19042.630; Ubuntu 20.04 installed from the store). Are you sure you are running on WSL2? (You can check this with `wsl --list --verbose`).> Almost surely it is Windows/WSL related, I'm not seeing this on Ubuntu > 20.04. > > One thing to check might be the FPU control word. In a Windows build, R > will set as it is on Unix, to use all 80 bits when values stay in FPU > registers, which is not the Windows default. This should not matter with > SSE anymore, but maybe something is still using the FPU. This is just > using inline assembly, so one could enable it as experiment. In > principle, this could be also due to some other things specific to > Windows that R works around in Windows builds, but doesn't in Linux > builds assuming they will not run on Windows.It does run on Linux. WSL2 runs a modified version of the Linux kernel on top of Hyper-V. Unless Bill is running WSL1, which runs on top of the Windows kernel with a syscall translation layer.> Other issues I had with WSL in the past (trying to build R and run > checks) included time-zones and surprising encodings, but I didn't check > recently. I would not use R on WSL unless my goal was to diagnose these > issues and see if they could be overcome on the R side. > > Best > Tomas-- I?aki ?car