[R] Difference between 32-bit and 64-bit version

[Thierry Onkelinx]

Dear all,

I'm a bit puzzled by the difference in an object when created in R 32-bit
and R 64-bit.

Consider the code below. test.rda is available at
https://drive.google.com/file/d/0BzBrlGSuB9n-NFBWeC1TR093Sms/view?usp=sharing

# Run in R 3.2.0 Windows 32-bit, lme4 1.1-8
library(lme4)
load("test.rda")
coef.32 <- coef(test)
save(coef.32, file = "32bit.rda")

# Run in R 3.2.0 Windows 64-bit, lme4 1.1-8
library(lme4)
load("~/test.rda")
coef.64 <- coef(test)
save(coef.64, file = "64bit.rda")


# Compare the results
# Run in R 3.2.0 Windows 32-bit, lme4 1.1-8
# Run in R 3.2.0 Windows 64-bit, lme4 1.1-8
library(lme4)
load("32bit.rda")
load("64bit.rda")
identical(coef.32, coef.64) # FALSE
identical(coef.32$fRow, coef.64$fRow) # FALSE
identical(coef.32$fLocation, coef.64$fLocation) # TRUE
identical(coef.32$fSubLocation, coef.64$fSubLocation) # TRUE

The first comparison is FALSE, because the second is FALSE. But why is the
second FALSE and the third and fourth TRUE?

My goal is the calculate a SHA1 hash on the coef(test) to track if the
coefficients of test have changed. I'd like to get the same hash on a
32-bit and 64-bit system. A simple hack would be to calculate the hash on
round(coef(test), 20). Is that a good or bad idea?

identical(round(coef.32$fRow, 20), round(coef.64$fRow, 20)) # TRUE

Best regards,

ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium

To call in the statistician after the experiment is done may be no more
than asking him to perform a post-mortem examination: he may be able to say
what the experiment died of. ~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data. ~ Roger Brinner
The combination of some data and an aching desire for an answer does not
ensure that a reasonable answer can be extracted from a given body of data.
~ John Tukey

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