49 lines
1.1 KiB
R
49 lines
1.1 KiB
R
library(numbers)
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library(microbenchmark)
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####
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# limit: Obere Grenze für die Summe der Primzahltripel
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#
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# Gibt die Anzahl der einmaligen Primzahltripel
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# bis zu einer oberen Grenze zurück.
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####
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simple87 <- function(limit) {
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primes <- Primes(1, ceiling(limit^(1/2)))
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x2 <- primes^2
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x3 <- primes^3
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x4 <- primes^4
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x2 <- x2[x2 < limit]
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x3 <- x3[x3 < limit]
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x4 <- x4[x4 < limit]
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x <- expand.grid(x2, x3, x4)
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xSums <- rowSums(x)
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length(unique(xSums[xSums < limit]))
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}
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# Wir erzeugen die Kombinationen selbst und
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# generieren eine Matrix über cbind()
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# Dadurch spart man sich die matrix <-> data.frame Konvertierung
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faster87<-function(limit) {
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primes <- Primes(1, ceiling(sqrt(limit)))
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x2 <- primes^2
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x3 <- primes^3
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x4 <- primes^4
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x2 <- x2[x2 < limit]
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x3 <- x3[x3 < limit]
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x4 <- x4[x4 < limit]
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x <- cbind(rep(x2, each=length(x3)*length(x4)),
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rep(x3, times=length(x2)*length(x4)),
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rep(x4, times=length(x2)*length(x3))
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)
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xSums <- rowSums(x)
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length(unique(xSums[xSums < limit]))
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}
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ress <- microbenchmark(simple87(5e7), faster87(5e7), times=500L)
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