[R] Different serialization and digest hash value of functions

[Holger Hoefling]

Hi,

I am using hash-values to cache certain results in R. This caching
also depends on the hash-value of the function that is being cached
(calculated using the digest package). I noticed that computations
that should already be cached are recomputed when switching from an
interactive session to a BATCH session. Therefore, I wrote a test
script

library(digest)
testfun <- function() {
    return(NULL)
}
testval <- "testval"
print(digest(testfun))
print(serialize(testfun, connection = NULL))

and executed it once using input-redirection from a file (testFile.R)
and once copying the code into an interactive R session. The
hash-values of the functions differ. As digest internally relies on
serialize, I also checked there and found that digest is not the
reason for the discrepancy. Instead, the serialized value of the
function already differs between the BATCH and inteactive sessions.

I was wondering if someone knows if
1. Is this a feature or a bug?
2. Is there a way to get consistent hash-values for functions between
BATCH and interactive sessions.

The output from the BATCH and interactive runs are below

Thanks

Holger Hoefling

---------------------------------
BATCH run:

$ R --vanilla < testFile.R

R version 3.1.0 (2014-04-10) -- "Spring Dance"
Copyright (C) 2014 The R Foundation for Statistical Computing
Platform: x86_64-unknown-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(digest)
> testfun <- function() {
+     return(NULL)
+ }
> print(digest(testfun))
[1] "b03160b9250f0d5b5bcce42bd86d8e56"
> print(serialize(testfun, connection = NULL))
 [1] 58 0a 00 00 00 02 00 03 01 00 00 02 03 00 00 00 04 03 00 00 00 fd 00 00 00
[26] fe 00 00 00 06 00 00 00 01 00 04 00 09 00 00 00 01 7b 00 00 00 02 00 00 00
[51] 06 00 00 00 01 00 04 00 09 00 00 00 06 72 65 74 75 72 6e 00 00 00 02 00 00
[76] 00 fe 00 00 00 fe 00 00 00 fe
>
>

----------------------------------------------
Interactive run:

$ R --vanilla

R version 3.1.0 (2014-04-10) -- "Spring Dance"
Copyright (C) 2014 The R Foundation for Statistical Computing
Platform: x86_64-unknown-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(digest)
> testfun <- function() {
+     return(NULL)
+ }
> print(digest(testfun))
[1] "fada482d2894088b079a8e56b7044862"
> print(serialize(testfun, connection = NULL))
  [1] 58 0a 00 00 00 02 00 03 01 00 00 02 03 00 00 00 06 03 00 00 04 02 00 00 00
 [26] 01 00 04 00 09 00 00 00 06 73 72 63 72 65 66 00 00 03 0d 00 00 00 08 00 00
 [51] 00 01 00 00 00 0c 00 00 00 03 00 00 00 01 00 00 00 0c 00 00 00 01 00 00 00
 [76] 01 00 00 00 03 00 00 04 02 00 00 00 01 00 04 00 09 00 00 00 07 73 72 63 66
[101] 69 6c 65 00 00 00 04 00 00 00 00 00 00 00 f2 00 00 04 02 00 00 00 01 00 04
[126] 00 09 00 00 00 05 6c 69 6e 65 73 00 00 00 10 00 00 00 01 00 04 00 09 00 00
[151] 00 2b 74 65 73 74 66 75 6e 20 3c 2d 20 66 75 6e 63 74 69 6f 6e 28 29 20 7b
[176] 0a 20 20 20 20 72 65 74 75 72 6e 28 4e 55 4c 4c 29 0a 7d 0a 00 00 04 02 00
[201] 00 00 01 00 04 00 09 00 00 00 08 66 69 6c 65 6e 61 6d 65 00 00 00 10 00 00
[226] 00 01 00 04 00 09 00 00 00 00 00 00 00 fe 00 00 00 fe 00 00 04 02 00 00 00
[251] 01 00 04 00 09 00 00 00 05 63 6c 61 73 73 00 00 00 10 00 00 00 02 00 04 00
[276] 09 00 00 00 0b 73 72 63 66 69 6c 65 63 6f 70 79 00 04 00 09 00 00 00 07 73
[301] 72 63 66 69 6c 65 00 00 00 fe 00 00 04 02 00 00 06 ff 00 00 00 10 00 00 00
[326] 01 00 04 00 09 00 00 00 06 73 72 63 72 65 66 00 00 00 fe 00 00 00 fe 00 00
[351] 00 fd 00 00 00 fe 00 00 02 06 00 00 04 02 00 00 01 ff 00 00 00 13 00 00 00
[376] 02 00 00 03 0d 00 00 00 08 00 00 00 01 00 00 00 17 00 00 00 01 00 00 00 17
[401] 00 00 00 17 00 00 00 17 00 00 00 01 00 00 00 01 00 00 04 02 00 00 02 ff 00
[426] 00 03 ff 00 00 04 02 00 00 06 ff 00 00 00 10 00 00 00 01 00 04 00 09 00 00
[451] 00 06 73 72 63 72 65 66 00 00 00 fe 00 00 03 0d 00 00 00 08 00 00 00 02 00
[476] 00 00 05 00 00 00 02 00 00 00 10 00 00 00 05 00 00 00 10 00 00 00 02 00 00
[501] 00 02 00 00 04 02 00 00 02 ff 00 00 03 ff 00 00 04 02 00 00 06 ff 00 00 00
[526] 10 00 00 00 01 00 04 00 09 00 00 00 06 73 72 63 72 65 66 00 00 00 fe 00 00
[551] 04 02 00 00 02 ff 00 00 03 ff 00 00 04 02 00 00 00 01 00 04 00 09 00 00 00
[576] 0b 77 68 6f 6c 65 53 72 63 72 65 66 00 00 03 0d 00 00 00 08 00 00 00 01 00
[601] 00 00 00 00 00 00 03 00 00 00 01 00 00 00 00 00 00 00 01 00 00 00 01 00 00
[626] 00 03 00 00 04 02 00 00 02 ff 00 00 03 ff 00 00 04 02 00 00 06 ff 00 00 00
[651] 10 00 00 00 01 00 04 00 09 00 00 00 06 73 72 63 72 65 66 00 00 00 fe 00 00
[676] 00 fe 00 00 00 01 00 04 00 09 00 00 00 01 7b 00 00 00 02 00 00 00 06 00 00
[701] 00 01 00 04 00 09 00 00 00 06 72 65 74 75 72 6e 00 00 00 02 00 00 00 fe 00
[726] 00 00 fe 00 00 00 fe
>