[Rd] Floating point issue
Olivier Benz
o||v|er@benz @end|ng |rom b-d@t@@ch
Tue Jul 19 14:59:25 CEST 2022
I found that quite puzzling indeed. Thanks for the references.
So in this case, the different results are not due to the architecture (M1 aka ARM64) but to the system/implementation.
> On 19 Jul 2022, at 14:22, Taras Zakharko <taras.zakharko using uzh.ch> wrote:
>
> Just a quick note of this in case someone finds Olivier's results puzzling. Standard ARM64 ABI (which Linux follows) defines long double as a 16-byte extended precision type. LLVM’s compiler-rt has a software implementation for doing operations on such types. Apple instead defines long double as identical to double in their ABIs.
>
> References
>
> https://developer.arm.com/documentation/ka004751/1-0
>
> https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms
>
>
>
>
>> On 19 Jul 2022, at 13:04, Olivier Benz <olivier.benz using b-data.ch> wrote:
>>
>> The difference between macOS 12.4 and Debian 11 (Docker, virtualization framework) running on a MacBook Pro (M1 Max).
>> -> `.Machine$sizeof.longdouble` on macOS returns 8 whereas on Debian 11 it returns 16.
>>
>> macOS 12.4 on MacBook Pro (M1 Max):
>> ``` r
>> .Machine
>> #> $double.eps
>> #> [1] 2.220446e-16
>> #>
>> #> $double.neg.eps
>> #> [1] 1.110223e-16
>> #>
>> #> $double.xmin
>> #> [1] 2.225074e-308
>> #>
>> #> $double.xmax
>> #> [1] 1.797693e+308
>> #>
>> #> $double.base
>> #> [1] 2
>> #>
>> #> $double.digits
>> #> [1] 53
>> #>
>> #> $double.rounding
>> #> [1] 5
>> #>
>> #> $double.guard
>> #> [1] 0
>> #>
>> #> $double.ulp.digits
>> #> [1] -52
>> #>
>> #> $double.neg.ulp.digits
>> #> [1] -53
>> #>
>> #> $double.exponent
>> #> [1] 11
>> #>
>> #> $double.min.exp
>> #> [1] -1022
>> #>
>> #> $double.max.exp
>> #> [1] 1024
>> #>
>> #> $integer.max
>> #> [1] 2147483647
>> #>
>> #> $sizeof.long
>> #> [1] 8
>> #>
>> #> $sizeof.longlong
>> #> [1] 8
>> #>
>> #> $sizeof.longdouble
>> #> [1] 8
>> #>
>> #> $sizeof.pointer
>> #> [1] 8
>>
>> bitC <- function(x) noquote(vapply(as.double(x), function(x) { # split one
>> double
>> b <- substr(as.character(rev(numToBits(x))), 2L, 2L)
>> paste0(c(b[1L], " ", b[2:12], " | ", b[13:64]), collapse = "")
>> }, ""))
>> bitC(10^25)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>> bitC(10000000000000000905969664)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010010
>> bitC(10000000000000000905969664 - 10^25)
>> #> [1] 0 10000011110 | 0000000000000000000000000000000000000000000000000000
>> bitC(1e25)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>> ```
>>
>> <sup>Created on 2022-07-19 by the [reprex package](https://reprex.tidyverse.org) (v2.0.1)</sup>
>>
>> <details style="margin-bottom:10px;">
>> <summary>
>> Session info
>> </summary>
>>
>> ``` r
>> sessioninfo::session_info()
>> #> ─ Session info ───────────────────────────────────────────────────────────────
>> #> setting value
>> #> version R version 4.2.1 (2022-06-23)
>> #> os macOS Monterey 12.4
>> #> system aarch64, darwin20
>> #> ui X11
>> #> language (EN)
>> #> collate en_US.UTF-8
>> #> ctype UTF-8
>> #> tz Europe/Copenhagen
>> #> date 2022-07-19
>> #> pandoc 2.18 @ /opt/local/bin/ (via rmarkdown)
>> #>
>> #> ─ Packages ───────────────────────────────────────────────────────────────────
>> #> package * version date (UTC) lib source
>> #> cli 3.3.0 2022-04-25 [1] CRAN (R 4.2.0)
>> #> digest 0.6.29 2021-12-01 [1] CRAN (R 4.2.0)
>> #> ellipsis 0.3.2 2021-04-29 [1] CRAN (R 4.2.0)
>> #> evaluate 0.15 2022-02-18 [1] CRAN (R 4.2.0)
>> #> fansi 1.0.3 2022-03-24 [1] CRAN (R 4.2.0)
>> #> fastmap 1.1.0 2021-01-25 [1] CRAN (R 4.2.0)
>> #> fs 1.5.2 2021-12-08 [1] CRAN (R 4.2.0)
>> #> glue 1.6.2 2022-02-24 [1] CRAN (R 4.2.0)
>> #> highr 0.9 2021-04-16 [1] CRAN (R 4.2.0)
>> #> htmltools 0.5.3 2022-07-18 [1] CRAN (R 4.2.1)
>> #> knitr 1.39 2022-04-26 [1] CRAN (R 4.2.0)
>> #> lifecycle 1.0.1 2021-09-24 [1] CRAN (R 4.2.0)
>> #> magrittr 2.0.3 2022-03-30 [1] CRAN (R 4.2.0)
>> #> pillar 1.8.0 2022-07-18 [1] CRAN (R 4.2.1)
>> #> pkgconfig 2.0.3 2019-09-22 [1] CRAN (R 4.2.0)
>> #> purrr 0.3.4 2020-04-17 [1] CRAN (R 4.2.0)
>> #> R.cache 0.15.0 2021-04-30 [1] CRAN (R 4.2.0)
>> #> R.methodsS3 1.8.2 2022-06-13 [1] CRAN (R 4.2.0)
>> #> R.oo 1.25.0 2022-06-12 [1] CRAN (R 4.2.0)
>> #> R.utils 2.12.0 2022-06-28 [1] CRAN (R 4.2.0)
>> #> reprex 2.0.1 2021-08-05 [1] CRAN (R 4.2.0)
>> #> rlang 1.0.4 2022-07-12 [1] CRAN (R 4.2.1)
>> #> rmarkdown 2.14 2022-04-25 [1] CRAN (R 4.2.0)
>> #> sessioninfo 1.2.2 2021-12-06 [1] CRAN (R 4.2.0)
>> #> stringi 1.7.8 2022-07-11 [1] CRAN (R 4.2.1)
>> #> stringr 1.4.0 2019-02-10 [1] CRAN (R 4.2.0)
>> #> styler 1.7.0 2022-03-13 [1] CRAN (R 4.2.0)
>> #> tibble 3.1.7 2022-05-03 [1] CRAN (R 4.2.0)
>> #> utf8 1.2.2 2021-07-24 [1] CRAN (R 4.2.0)
>> #> vctrs 0.4.1 2022-04-13 [1] CRAN (R 4.2.0)
>> #> withr 2.5.0 2022-03-03 [1] CRAN (R 4.2.0)
>> #> xfun 0.31 2022-05-10 [1] CRAN (R 4.2.0)
>> #> yaml 2.3.5 2022-02-21 [1] CRAN (R 4.2.0)
>> #>
>> #> [1] /Users/benz0li/Library/R/arm64/4.2/library
>> #> [2] /Library/Frameworks/R.framework/Versions/4.2-arm64/Resources/library
>> #>
>> #> ──────────────────────────────────────────────────────────────────────────────
>> ```
>>
>> </details>
>>
>> Debian 11 (Docker, virtualization framework) on MacBook Pro (M1 Max)
>> ``` r
>> .Machine
>> #> $double.eps
>> #> [1] 2.220446e-16
>> #>
>> #> $double.neg.eps
>> #> [1] 1.110223e-16
>> #>
>> #> $double.xmin
>> #> [1] 2.225074e-308
>> #>
>> #> $double.xmax
>> #> [1] 1.797693e+308
>> #>
>> #> $double.base
>> #> [1] 2
>> #>
>> #> $double.digits
>> #> [1] 53
>> #>
>> #> $double.rounding
>> #> [1] 5
>> #>
>> #> $double.guard
>> #> [1] 0
>> #>
>> #> $double.ulp.digits
>> #> [1] -52
>> #>
>> #> $double.neg.ulp.digits
>> #> [1] -53
>> #>
>> #> $double.exponent
>> #> [1] 11
>> #>
>> #> $double.min.exp
>> #> [1] -1022
>> #>
>> #> $double.max.exp
>> #> [1] 1024
>> #>
>> #> $integer.max
>> #> [1] 2147483647
>> #>
>> #> $sizeof.long
>> #> [1] 8
>> #>
>> #> $sizeof.longlong
>> #> [1] 8
>> #>
>> #> $sizeof.longdouble
>> #> [1] 16
>> #>
>> #> $sizeof.pointer
>> #> [1] 8
>> #>
>> #> $longdouble.eps
>> #> [1] 1.92593e-34
>> #>
>> #> $longdouble.neg.eps
>> #> [1] 9.62965e-35
>> #>
>> #> $longdouble.digits
>> #> [1] 113
>> #>
>> #> $longdouble.rounding
>> #> [1] 5
>> #>
>> #> $longdouble.guard
>> #> [1] 0
>> #>
>> #> $longdouble.ulp.digits
>> #> [1] -112
>> #>
>> #> $longdouble.neg.ulp.digits
>> #> [1] -113
>> #>
>> #> $longdouble.exponent
>> #> [1] 15
>> #>
>> #> $longdouble.min.exp
>> #> [1] -16382
>> #>
>> #> $longdouble.max.exp
>> #> [1] 16384
>>
>> bitC <- function(x) noquote(vapply(as.double(x), function(x) { # split one
>> double
>> b <- substr(as.character(rev(numToBits(x))), 2L, 2L)
>> paste0(c(b[1L], " ", b[2:12], " | ", b[13:64]), collapse = "")
>> }, ""))
>> bitC(10^25)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>> bitC(10000000000000000905969664)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>> bitC(10000000000000000905969664 - 10^25)
>> #> [1] 0 00000000000 | 0000000000000000000000000000000000000000000000000000
>> bitC(1e25)
>> #> [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>> ```
>>
>> <sup>Created on 2022-07-19 by the [reprex package](https://reprex.tidyverse.org) (v2.0.1)</sup>
>>
>> <details style="margin-bottom:10px;">
>> <summary>
>> Session info
>> </summary>
>>
>> ``` r
>> sessioninfo::session_info()
>> #> ─ Session info ───────────────────────────────────────────────────────────────
>> #> setting value
>> #> version R version 4.2.1 (2022-06-23)
>> #> os Debian GNU/Linux 11 (bullseye)
>> #> system aarch64, linux-gnu
>> #> ui X11
>> #> language (EN)
>> #> collate en_US.UTF-8
>> #> ctype en_US.UTF-8
>> #> tz Etc/UTC
>> #> date 2022-07-19
>> #> pandoc 2.18 @ /usr/bin/ (via rmarkdown)
>> #>
>> #> ─ Packages ───────────────────────────────────────────────────────────────────
>> #> package * version date (UTC) lib source
>> #> cli 3.3.0 2022-04-25 [2] CRAN (R 4.2.1)
>> #> crayon 1.5.1 2022-03-26 [2] CRAN (R 4.2.1)
>> #> digest 0.6.29 2021-12-01 [2] CRAN (R 4.2.1)
>> #> ellipsis 0.3.2 2021-04-29 [2] CRAN (R 4.2.1)
>> #> evaluate 0.15 2022-02-18 [2] CRAN (R 4.2.1)
>> #> fansi 1.0.3 2022-03-24 [2] CRAN (R 4.2.1)
>> #> fastmap 1.1.0 2021-01-25 [2] CRAN (R 4.2.1)
>> #> fs 1.5.2 2021-12-08 [2] CRAN (R 4.2.1)
>> #> glue 1.6.2 2022-02-24 [2] CRAN (R 4.2.1)
>> #> highr 0.9 2021-04-16 [2] CRAN (R 4.2.1)
>> #> htmltools 0.5.2 2021-08-25 [2] CRAN (R 4.2.1)
>> #> knitr 1.39 2022-04-26 [2] CRAN (R 4.2.1)
>> #> lifecycle 1.0.1 2021-09-24 [2] CRAN (R 4.2.1)
>> #> magrittr 2.0.3 2022-03-30 [2] CRAN (R 4.2.1)
>> #> pillar 1.7.0 2022-02-01 [2] CRAN (R 4.2.1)
>> #> pkgconfig 2.0.3 2019-09-22 [2] CRAN (R 4.2.1)
>> #> purrr 0.3.4 2020-04-17 [2] CRAN (R 4.2.1)
>> #> R.cache 0.15.0 2021-04-30 [2] CRAN (R 4.2.1)
>> #> R.methodsS3 1.8.2 2022-06-13 [2] CRAN (R 4.2.1)
>> #> R.oo 1.25.0 2022-06-12 [2] CRAN (R 4.2.1)
>> #> R.utils 2.12.0 2022-06-28 [2] CRAN (R 4.2.1)
>> #> reprex 2.0.1 2021-08-05 [2] CRAN (R 4.2.1)
>> #> rlang 1.0.4 2022-07-12 [2] CRAN (R 4.2.1)
>> #> rmarkdown 2.14 2022-04-25 [2] CRAN (R 4.2.1)
>> #> sessioninfo 1.2.2 2021-12-06 [2] CRAN (R 4.2.1)
>> #> stringi 1.7.8 2022-07-11 [2] CRAN (R 4.2.1)
>> #> stringr 1.4.0 2019-02-10 [2] CRAN (R 4.2.1)
>> #> styler 1.7.0 2022-03-13 [2] CRAN (R 4.2.1)
>> #> tibble 3.1.7 2022-05-03 [2] CRAN (R 4.2.1)
>> #> utf8 1.2.2 2021-07-24 [2] CRAN (R 4.2.1)
>> #> vctrs 0.4.1 2022-04-13 [2] CRAN (R 4.2.1)
>> #> withr 2.5.0 2022-03-03 [2] CRAN (R 4.2.1)
>> #> xfun 0.31 2022-05-10 [2] CRAN (R 4.2.1)
>> #> yaml 2.3.5 2022-02-21 [2] CRAN (R 4.2.1)
>> #>
>> #> [1] /home/benz0li/R/aarch64-unknown-linux-gnu-library/4.2
>> #> [2] /usr/local/lib/R/site-library
>> #> [3] /usr/local/lib/R/library
>> #>
>> #> ──────────────────────────────────────────────────────────────────────────────
>> ```
>>
>> </details>
>>
>>> On 10 Jul 2022, at 22:23, Bill Dunlap <williamwdunlap using gmail.com> wrote:
>>>
>>> The following function, 'bitC' from ?numToBits, displays the bits in a
>>> double precision number, separated into the sign bit, the 11 exponent bits,
>>> and the 52 bits in the mantissa. I've shown the results with your numbers
>>> from R-2.4.0 on my Windows 11 Lenovo laptop: what do you get?
>>>
>>>> bitC <- function(x) noquote(vapply(as.double(x), function(x) { # split
>>> one double
>>> + b <- substr(as.character(rev(numToBits(x))), 2L, 2L)
>>> + paste0(c(b[1L], " ", b[2:12], " | ", b[13:64]), collapse = "")
>>> + }, ""))
>>>> bitC(10^25)
>>> # [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>>>> bitC(10000000000000000905969664)
>>> # [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>>>> bitC(10000000000000000905969664 - 10^25)
>>> # [1] 0 00000000000 | 0000000000000000000000000000000000000000000000000000
>>>> bitC(1e25)
>>> # [1] 0 10001010010 | 0000100010110010101000101100001010000000001010010001
>>>
>>> -Bill
>>>
>>> On Sun, Jul 10, 2022 at 7:00 AM Antoine Fabri <antoine.fabri using gmail.com>
>>> wrote:
>>>
>>>> Dear r-devel,
>>>>
>>>> For some numbers, the printed value is not equivalent to the input :
>>>>
>>>> options(scipen = 999)
>>>> ## GOOD
>>>> 1e24
>>>> #> [1] 999999999999999983222784
>>>> 1e24 == 999999999999999983222784
>>>> #> [1] TRUE
>>>>
>>>> ## BAD
>>>> 1e25
>>>> #> [1] 10000000000000000905969664
>>>> 1e25 == 10000000000000000905969664
>>>> #> [1] FALSE
>>>>
>>>> ## STILL BAD
>>>> 10000000000000000905969664
>>>> #> [1] 10000000000000003053453312
>>>>
>>>> ## GOOD AGAIN
>>>> 10000000000000003053453312
>>>> #> [1] 10000000000000003053453312
>>>>
>>>> # Additionally
>>>> 10000000000000000000000000 == 1e25
>>>> #> [1] FALSE
>>>>
>>>> Are these bugs ?
>>>>
>>>> [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
>>>> R-devel using r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-devel using r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>> --
>> benz0li.b-data.io | @benz0li | olivier.benz using b-data.ch
>>
>> ______________________________________________
>> R-devel using r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>
> [[alternative HTML version deleted]]
>
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--
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