# Name

**HPL_perm** Combine 2 index arrays - Generate the permutation.
# Synopsis

`#include "hpl.h"`

`void`

`HPL_perm(`

`const int`

`N`

,
`int *`

`LINDXA`

,
`int *`

`LINDXAU`

,
`int *`

`IWORK`

`);`

# Description

**HPL_perm**
combines two index arrays and generate the corresponding
permutation. First, this function computes the inverse of LINDXA, and
then combine it with LINDXAU. Second, in order to be able to perform
the permutation in place, LINDXAU is overwritten by the sequence of
permutation producing the same result. What we ultimately want to
achieve is: U[LINDXAU[i]] := U[LINDXA[i]] for i in [0..N). After the
call to this function, this in place permutation can be performed by
for i in [0..N) swap U[i] with U[LINDXAU[i]].
# Arguments

N (global input) const int
On entry, N specifies the length of the arrays LINDXA and
LINDXAU. N should be at least zero.

LINDXA (global input/output) int *
On entry, LINDXA is an array of dimension N containing the
source indexes. On exit, LINDXA contains the combined index
array.

LINDXAU (global input/output) int *
On entry, LINDXAU is an array of dimension N containing the
target indexes. On exit, LINDXAU contains the sequence of
permutation, that should be applied in increasing order to
permute the underlying array U in place.

IWORK (workspace) int *
On entry, IWORK is a workarray of dimension N.

# See Also

HPL_plindx1,
HPL_pdlaswp01N,
HPL_pdlaswp01T.