eigs_real_gen <- function(A, n, k, which, sigma, opts, mattype, extra_args = list())
{
# Check whether 'A' is a square matrix
# Skip this step if A is a function
if (!is.null(dim(A)))
{
if (nrow(A) != ncol(A) | nrow(A) != n)
stop("'A' must be a square matrix of size n")
}
# eigs() is not suitable for small matrices
if (n < 3)
stop("dimension of 'A' must be at least 3")
# If >= n-1 eigenvalues are requested, call eigen() instead,
# and give a warning
if (k == n - 1)
{
res = eigen(A, only.values = identical(opts$retvec, FALSE))
exclude = switch(which,
LM = n,
SM = 1,
LR = which.min(Re(res$values)),
SR = which.max(Re(res$values)),
LI = which.min(abs(Im(res$values))),
SI = which.max(abs(Im(res$values))))
warning("(n-1) eigenvalues are requested, eigen() is used instead")
return(list(values = res$values[-exclude],
vectors = res$vectors[, -exclude],
nconv = n, niter = 0))
}
if (k == n)
{
res = eigen(A, only.values = identical(opts$retvec, FALSE))
warning("all eigenvalues are requested, eigen() is used instead")
return(c(res, nconv = n, niter = 0))
}
# Matrix will be passed to C++, so we need to check the type.
# Convert the matrix type if A is stored other than double.
#
# However, for sparse matrices defined in Matrix package,
# they are always double, so we can omit this check.
if (mattype == "matrix" & typeof(A) != "double")
{
mode(A) = "double"
}
# Check the value of 'k'
if (k <= 0 | k >= n - 1)
stop("'k' must satisfy 0 < k < nrow(A) - 1.\nTo calculate all eigenvalues, try eigen()")
# Check sigma
# workmode == 1: ordinary
# workmode == 3: Shift-invert mode
if (is.null(sigma))
{
workmode = "regular"
sigma = 0
} else {
if(abs(Im(sigma)) < 1e-16)
{
sigma = Re(sigma)
workmode = "real_shift"
} else {
workmode = "complex_shift"
}
}
# Arguments to be passed to Spectra
spectra.param = list(which = which,
ncv = min(n, max(2 * k + 1, 20)),
tol = 1e-10,
maxitr = 1000,
retvec = TRUE,
user_initvec = FALSE,
sigmar = Re(sigma[1]),
sigmai = Im(sigma[1]))
# Check the value of 'which'
eigenv.type = c("LM", "SM", "LR", "SR", "LI", "SI")
if (!(spectra.param$which %in% eigenv.type))
{
stop(sprintf("argument 'which' must be one of\n%s",
paste(eigenv.type, collapse = ", ")))
}
# Update parameters from 'opts' argument
spectra.param[names(opts)] = opts
spectra.param$which = EIGS_RULE[spectra.param$which]
# Any other arguments passed to C++ code, for example use_lower and fun_args
spectra.param = c(spectra.param, as.list(extra_args))
# Check the value of 'ncv'
if (spectra.param$ncv < k + 2 | spectra.param$ncv > n)
stop("'opts$ncv' must be >= k+2 and <= nrow(A)")
# Check the value of 'initvec'
if ("initvec" %in% names(spectra.param))
{
if(length(spectra.param$initvec) != n)
stop("'opt$initvec' must have length n")
spectra.param$initvec = as.numeric(spectra.param$initvec)
spectra.param$user_initvec = TRUE
}
# Call the C++ function
fun = switch(workmode,
regular = "eigs_gen",
real_shift = "eigs_real_shift_gen",
complex_shift = "eigs_complex_shift_gen",
stop("unknown work mode"))
dot_call_args = list(
fun,
A, as.integer(n), as.integer(k), as.list(spectra.param), as.integer(MAT_TYPE[mattype]),
PACKAGE = "RSpectra"
)
do.call(.Call, args = dot_call_args)
}
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