primeFactorize | R Documentation |
Implementation of Pollard's rho algorithm for generating the prime factorization. The algorithm is based on the "factorize.c" source file from the gmp library found here https://gmplib.org.
primeFactorize(v, namedList = FALSE, nThreads = NULL)
v |
Vector of integers or numeric values. Non-integral values will be cured to whole numbers. |
namedList |
Logical flag. If |
nThreads |
Specific number of threads to be used. The default is |
As noted in the Description section above, this algorithm is based on the "factorize.c" source code from the gmp library. Much of the code in RcppAlgos::primeFactorize is a straightforward translation from multiple precision C data types to standard C++ data types. A crucial part of the algorithm's efficiency is based on quickly determining primality, which is easily computed with gmp. However, with standard C++, this is quite challenging. Much of the research for RcppAlgos::primeFactorize was focused on developing an algorithm that could accurately and efficiently compute primality.
For more details, see the documentation for isPrimeRcpp
.
Returns an unnamed vector if length(v) == 1
regardless of the value of namedList
. If v < 2^{31}
, the class of the returned vector will be integer, otherwise the class will be numeric.
If length(v) > 1
, a named/unnamed list of vectors will be returned. If max(bound1, bound2)
< 2^{31}
, the class of each vector will be integer, otherwise the class will be numeric.
The maximum value for each element in v
is 2^{53} - 1
.
Joseph Wood
primeFactorizeSieve
, factorize
## Get the prime factorization of a single number
primeFactorize(10^8)
## Or get the prime factorization of many numbers
set.seed(29)
myVec <- sample(-1000000:1000000, 1000)
system.time(pFacs <- primeFactorize(myVec))
## Return named list
pFacsWithNames <- primeFactorize(myVec, namedList = TRUE)
## Using nThreads
system.time(primeFactorize(myVec, nThreads = 2))
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