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Annotation of rpl/lapack/lapack/dlamrg.f, revision 1.7

1.1       bertrand    1:       SUBROUTINE DLAMRG( N1, N2, A, DTRD1, DTRD2, INDEX )
                      2: *
                      3: *  -- LAPACK routine (version 3.2) --
                      4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                      5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                      6: *     November 2006
                      7: *
                      8: *     .. Scalar Arguments ..
                      9:       INTEGER            DTRD1, DTRD2, N1, N2
                     10: *     ..
                     11: *     .. Array Arguments ..
                     12:       INTEGER            INDEX( * )
                     13:       DOUBLE PRECISION   A( * )
                     14: *     ..
                     15: *
                     16: *  Purpose
                     17: *  =======
                     18: *
                     19: *  DLAMRG will create a permutation list which will merge the elements
                     20: *  of A (which is composed of two independently sorted sets) into a
                     21: *  single set which is sorted in ascending order.
                     22: *
                     23: *  Arguments
                     24: *  =========
                     25: *
                     26: *  N1     (input) INTEGER
                     27: *  N2     (input) INTEGER
                     28: *         These arguements contain the respective lengths of the two
                     29: *         sorted lists to be merged.
                     30: *
                     31: *  A      (input) DOUBLE PRECISION array, dimension (N1+N2)
                     32: *         The first N1 elements of A contain a list of numbers which
                     33: *         are sorted in either ascending or descending order.  Likewise
                     34: *         for the final N2 elements.
                     35: *
                     36: *  DTRD1  (input) INTEGER
                     37: *  DTRD2  (input) INTEGER
                     38: *         These are the strides to be taken through the array A.
                     39: *         Allowable strides are 1 and -1.  They indicate whether a
                     40: *         subset of A is sorted in ascending (DTRDx = 1) or descending
                     41: *         (DTRDx = -1) order.
                     42: *
                     43: *  INDEX  (output) INTEGER array, dimension (N1+N2)
                     44: *         On exit this array will contain a permutation such that
                     45: *         if B( I ) = A( INDEX( I ) ) for I=1,N1+N2, then B will be
                     46: *         sorted in ascending order.
                     47: *
                     48: *  =====================================================================
                     49: *
                     50: *     .. Local Scalars ..
                     51:       INTEGER            I, IND1, IND2, N1SV, N2SV
                     52: *     ..
                     53: *     .. Executable Statements ..
                     54: *
                     55:       N1SV = N1
                     56:       N2SV = N2
                     57:       IF( DTRD1.GT.0 ) THEN
                     58:          IND1 = 1
                     59:       ELSE
                     60:          IND1 = N1
                     61:       END IF
                     62:       IF( DTRD2.GT.0 ) THEN
                     63:          IND2 = 1 + N1
                     64:       ELSE
                     65:          IND2 = N1 + N2
                     66:       END IF
                     67:       I = 1
                     68: *     while ( (N1SV > 0) & (N2SV > 0) )
                     69:    10 CONTINUE
                     70:       IF( N1SV.GT.0 .AND. N2SV.GT.0 ) THEN
                     71:          IF( A( IND1 ).LE.A( IND2 ) ) THEN
                     72:             INDEX( I ) = IND1
                     73:             I = I + 1
                     74:             IND1 = IND1 + DTRD1
                     75:             N1SV = N1SV - 1
                     76:          ELSE
                     77:             INDEX( I ) = IND2
                     78:             I = I + 1
                     79:             IND2 = IND2 + DTRD2
                     80:             N2SV = N2SV - 1
                     81:          END IF
                     82:          GO TO 10
                     83:       END IF
                     84: *     end while
                     85:       IF( N1SV.EQ.0 ) THEN
                     86:          DO 20 N1SV = 1, N2SV
                     87:             INDEX( I ) = IND2
                     88:             I = I + 1
                     89:             IND2 = IND2 + DTRD2
                     90:    20    CONTINUE
                     91:       ELSE
                     92: *     N2SV .EQ. 0
                     93:          DO 30 N2SV = 1, N1SV
                     94:             INDEX( I ) = IND1
                     95:             I = I + 1
                     96:             IND1 = IND1 + DTRD1
                     97:    30    CONTINUE
                     98:       END IF
                     99: *
                    100:       RETURN
                    101: *
                    102: *     End of DLAMRG
                    103: *
                    104:       END