Consider:
> foob <- as.bigz(5:7)
> min(foob)
Big Integer ('bigz') :
[1] 5
> .bigz2mpfr(prev)
1 'mpfr' number of precision 4 bits
[1] 5
> min(.bigz2mpfr(foob))
1 'mpfr' number of precision 53 bits
[1] 5
> min(mpfr(5:7,5))
1 'mpfr' number of precision 53 bits
[1] 5
I know that the 'min' method for mpfr objects somehow dives into the 'min' method for bigz or bigq - class objects but can't figure out how or why the precision gets bumped up to such a larg value. Can anyone detail what's happening behind the curtain?
Addendum: this only seems to happen if I start out with mpfr objects with very small precision. If I start with, say foo <- mpfr(1:5, prec = 60) then I don't see any jump in the precision value.
These seem to be the default options, by type, absent setting precBit as you do above:
debug at /home/chris/r_TMPDIR/RtmpK4UkSw/R.INSTALL422c7408a8298/Rmpfr/R/mpfr.R#656: if (is.logical(x)) 2L else if (is.raw(x)) {
if (is.object(x)) {
if (inherits(x, "bigz"))
frexpZ(x)$exp
else if (inherits(x, "bigq")) {
if (missing(bigq.)) {
warning("default precision for 'bigq' arbitrarily chosen as ",
bigq.)
bigq.
}
else as.integer(bigq.)
}
else 8L
}
else 8L
} else {
if (!doNumeric)
stop("must specify 'precBits' for numeric 'x' when 'doNumeric' is false")
if (is.integer(x))
32L
else if (is.double(x))
53L
else if (length(x) == 0)
mpfr_default_prec()
else stop(sprintf("cannot determine 'precBits' for x of type '%s'",
typeof(x)))
}
Browse[4]> ls()
[1] "base" "bigq." "doNumeric" "is.mpfr" "x"
Browse[4]> s
Greater or less precision can be requested.
?getPrec # get you into otherwise unexported utilities for poking around
f5 <- getPrec(6:10, base = 10, doNumeric = TRUE, is.mpfr = NA, bigq. = 128L)
> f5
[1] 32
> f6 <- getPrec(6.5:10, base = 10, doNumeric = TRUE, is.mpfr = NA, bigq. = 128L)
> f6
[1] 53
Still head scratching on extracting from result for sets...