# NOT RUN {
pochMpfr(100, 4) == 100*101*102*103 # TRUE
a <- 100:110
pochMpfr(a, 10) # exact (but too high precision)
x <- mpfr(a, 70)# should be enough
(px <- pochMpfr(x, 10)) # the same as above (needing only 70 bits)
stopifnot(pochMpfr(a, 10) == px,
px[1] ==prod(mpfr(100:109, 100)))# used to fail
(c1 <- chooseMpfr(1000:997, 60)) # -> automatic "correct" precision
stopifnot(all.equal(c1, choose(1000:997, 60), tolerance=1e-12))
## --- Experimenting & Checking
n.set <- c(1:10, 20, 50:55, 100:105, 200:203, 300:303, 500:503,
699:702, 999:1001)
if(!Rmpfr:::doExtras()) { ## speed up: smaller set
n. <- n.set[-(1:10)]
n.set <- c(1:10, n.[ c(TRUE, diff(n.) > 1)])
}
C1 <- C2 <- numeric(length(n.set))
for(i.n in seq_along(n.set)) {
cat(n <- n.set[i.n],":")
C1[i.n] <- system.time(c.c <- chooseMpfr.all(n) )[1]
C2[i.n] <- system.time(c.2 <- chooseMpfr(n, 1:n))[1]
stopifnot(is.whole(c.c), c.c == c.2,
if(n > 60) TRUE else all.equal(c.c, choose(n, 1:n), tolerance = 1e-15))
cat(" [Ok]\n")
}
matplot(n.set, cbind(C1,C2), type="b", log="xy",
xlab = "n", ylab = "system.time(.) [s]")
legend("topleft", c("chooseMpfr.all(n)", "chooseMpfr(n, 1:n)"),
pch=as.character(1:2), col=1:2, lty=1:2, bty="n")
## Currently, chooseMpfr.all() is faster only for large n (>= 300)
## That would change if we used C-code for the *.all() version
# }
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