# 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.