The functions rely on reblocking across different BLACS contexts. If
i is not empty, then the input distributed matrix will be
redistributed along context 1, where extracting/deleting rows does not
destroy block-cyclicality. Likewise, if j is not empty, then the
input distributed matrix will be redistributed along context 2. When
extraction is complete, the matrix will be redistributed across its input
context.
# S3 method for ddmatrix
head(x, n = 6L, ...)# S3 method for ddmatrix
tail(x, n = 6L, ...)
numeric distributed matrix.
a single integer. If positive, size for the resulting object:
number of elements for a vector (including lists), rows for a matrix or data
frame or lines for a function. If negative, all but the n last/first
number of elements of x.
additional arguments.
Returns a distributed matrix.