Sorts an integer array by nondecreasing absolute value and return the permutation that rearranges the array.

Required Arguments

IA — Integer vector of length N containing the array to be sorted.   (Input)

IB — Integer vector of length N containing the sorted array.   (Output)
If IA is not needed, IA and IB can share the same storage locations.

IPERM — Vector of length N.   (Input/Output)
On input, IPERM should be initialized to the values 1, 2, …, N. On output, IPERM contains a record of permutations made on the vector IA.

Optional Arguments

N — Number of elements in the array to be sorted.   (Input)
Default: N = size (IA,1).

FORTRAN 90 Interface

Generic:                              CALL SVIBP (IA, IB, IPERM [,…])

Specific:                             The specific interface name is S_SVIBP.

FORTRAN 77 Interface

Single:                                CALL SVIBP (N, IA, IB, IPERM)

Description

Routine SVIBP sorts the elements of an integer array, A, into ascending order by absolute value, keeping a record in P of the permutations to the array A. That is, the elements of P are moved in the same manner as are the elements in A as A is being sorted. The routine SVIBP uses the algorithm discussed in SVRGN. On completion, Aj ≤ Ai for j < i.

Comments

For wider applicability, integers (1, 2, …, N) that are to be associated with IA(I) for I = 1, 2, …, N may be entered into IPERM(I) in any order. Note that these integers must be unique.

Example

This example sorts the 10-element array IA by absolute value.

 

      USE SVIBP_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    N, U, NOUT, J

      PARAMETER  (N=10)

      INTEGER    IA(N), IB(N), IPERM(N)

!                                 Set values for  IA

!     IA    = ( 10  9  8  7  6  5  -4  3  -2  1 )

!

!     IPERM = ( 1  2  3  4  5  6  7  8  9  10 )

!

      DATA IA/10, 9, 8, 7, 6, 5, -4, 3, -2, 1/

      DATA IPERM/1, 2, 3, 4, 5, 6, 7, 8, 9, 10/

!                                 Sort IA by absolute value into IB

      CALL SVIBP (IA, IB, IPERM)

!                                 Print results

      CALL UMACH (2,NOUT)

      WRITE (NOUT, 99998) (IB(J),J=1,N)

      WRITE (NOUT, 99999) (IPERM(J),J=1,N)

!

99998 FORMAT ('  The output vector is:', /, 10(1X,I5))

99999 FORMAT ('  The permutation vector is:', /, 10(1X,I5))

      END

Output

 

The Output vector is:
1    -2     3    -4     5     6     7     8     9    10

The permutation vector is:
10     9     8     7     6     5     4     3     2     1

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