root / src / lapack / double / dlasrt.f @ 7
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SUBROUTINE DLASRT( ID, N, D, INFO ) |
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* |
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* -- LAPACK routine (version 3.2) -- |
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* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
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* November 2006 |
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* |
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* .. Scalar Arguments .. |
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CHARACTER ID |
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INTEGER INFO, N |
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* .. |
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* .. Array Arguments .. |
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DOUBLE PRECISION D( * ) |
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* .. |
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* |
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* Purpose |
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* ======= |
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* |
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* Sort the numbers in D in increasing order (if ID = 'I') or |
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* in decreasing order (if ID = 'D' ). |
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* |
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* Use Quick Sort, reverting to Insertion sort on arrays of |
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* size <= 20. Dimension of STACK limits N to about 2**32. |
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* |
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* Arguments |
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* ========= |
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* |
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* ID (input) CHARACTER*1 |
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* = 'I': sort D in increasing order; |
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* = 'D': sort D in decreasing order. |
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* |
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* N (input) INTEGER |
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* The length of the array D. |
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* |
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* D (input/output) DOUBLE PRECISION array, dimension (N) |
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* On entry, the array to be sorted. |
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* On exit, D has been sorted into increasing order |
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* (D(1) <= ... <= D(N) ) or into decreasing order |
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* (D(1) >= ... >= D(N) ), depending on ID. |
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* |
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* INFO (output) INTEGER |
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* = 0: successful exit |
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* < 0: if INFO = -i, the i-th argument had an illegal value |
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* |
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* ===================================================================== |
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* |
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* .. Parameters .. |
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INTEGER SELECT |
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PARAMETER ( SELECT = 20 ) |
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* .. |
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* .. Local Scalars .. |
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INTEGER DIR, ENDD, I, J, START, STKPNT |
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DOUBLE PRECISION D1, D2, D3, DMNMX, TMP |
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* .. |
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* .. Local Arrays .. |
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INTEGER STACK( 2, 32 ) |
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* .. |
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* .. External Functions .. |
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LOGICAL LSAME |
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EXTERNAL LSAME |
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* .. |
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* .. External Subroutines .. |
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EXTERNAL XERBLA |
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* .. |
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* .. Executable Statements .. |
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* |
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* Test the input paramters. |
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* |
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INFO = 0 |
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DIR = -1 |
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IF( LSAME( ID, 'D' ) ) THEN |
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DIR = 0 |
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ELSE IF( LSAME( ID, 'I' ) ) THEN |
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DIR = 1 |
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END IF |
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IF( DIR.EQ.-1 ) THEN |
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INFO = -1 |
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ELSE IF( N.LT.0 ) THEN |
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INFO = -2 |
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END IF |
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IF( INFO.NE.0 ) THEN |
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CALL XERBLA( 'DLASRT', -INFO ) |
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RETURN |
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END IF |
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* |
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* Quick return if possible |
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* |
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IF( N.LE.1 ) |
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$ RETURN |
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* |
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STKPNT = 1 |
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STACK( 1, 1 ) = 1 |
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STACK( 2, 1 ) = N |
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10 CONTINUE |
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START = STACK( 1, STKPNT ) |
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ENDD = STACK( 2, STKPNT ) |
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STKPNT = STKPNT - 1 |
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IF( ENDD-START.LE.SELECT .AND. ENDD-START.GT.0 ) THEN |
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* |
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* Do Insertion sort on D( START:ENDD ) |
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* |
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IF( DIR.EQ.0 ) THEN |
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* |
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* Sort into decreasing order |
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* |
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DO 30 I = START + 1, ENDD |
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DO 20 J = I, START + 1, -1 |
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IF( D( J ).GT.D( J-1 ) ) THEN |
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DMNMX = D( J ) |
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D( J ) = D( J-1 ) |
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D( J-1 ) = DMNMX |
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ELSE |
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GO TO 30 |
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END IF |
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20 CONTINUE |
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30 CONTINUE |
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* |
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ELSE |
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* |
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* Sort into increasing order |
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* |
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DO 50 I = START + 1, ENDD |
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DO 40 J = I, START + 1, -1 |
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IF( D( J ).LT.D( J-1 ) ) THEN |
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DMNMX = D( J ) |
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D( J ) = D( J-1 ) |
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D( J-1 ) = DMNMX |
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ELSE |
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GO TO 50 |
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END IF |
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40 CONTINUE |
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50 CONTINUE |
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* |
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END IF |
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* |
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ELSE IF( ENDD-START.GT.SELECT ) THEN |
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* |
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* Partition D( START:ENDD ) and stack parts, largest one first |
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* |
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* Choose partition entry as median of 3 |
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* |
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D1 = D( START ) |
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D2 = D( ENDD ) |
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I = ( START+ENDD ) / 2 |
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D3 = D( I ) |
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IF( D1.LT.D2 ) THEN |
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IF( D3.LT.D1 ) THEN |
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DMNMX = D1 |
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ELSE IF( D3.LT.D2 ) THEN |
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DMNMX = D3 |
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ELSE |
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DMNMX = D2 |
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END IF |
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ELSE |
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IF( D3.LT.D2 ) THEN |
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DMNMX = D2 |
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ELSE IF( D3.LT.D1 ) THEN |
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DMNMX = D3 |
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ELSE |
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DMNMX = D1 |
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END IF |
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END IF |
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* |
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IF( DIR.EQ.0 ) THEN |
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* |
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* Sort into decreasing order |
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* |
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I = START - 1 |
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J = ENDD + 1 |
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60 CONTINUE |
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70 CONTINUE |
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J = J - 1 |
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IF( D( J ).LT.DMNMX ) |
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$ GO TO 70 |
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80 CONTINUE |
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I = I + 1 |
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IF( D( I ).GT.DMNMX ) |
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$ GO TO 80 |
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IF( I.LT.J ) THEN |
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TMP = D( I ) |
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D( I ) = D( J ) |
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D( J ) = TMP |
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GO TO 60 |
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END IF |
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IF( J-START.GT.ENDD-J-1 ) THEN |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = START |
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STACK( 2, STKPNT ) = J |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = J + 1 |
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STACK( 2, STKPNT ) = ENDD |
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ELSE |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = J + 1 |
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STACK( 2, STKPNT ) = ENDD |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = START |
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STACK( 2, STKPNT ) = J |
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END IF |
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ELSE |
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* |
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* Sort into increasing order |
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* |
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I = START - 1 |
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J = ENDD + 1 |
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90 CONTINUE |
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100 CONTINUE |
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J = J - 1 |
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IF( D( J ).GT.DMNMX ) |
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$ GO TO 100 |
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110 CONTINUE |
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I = I + 1 |
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IF( D( I ).LT.DMNMX ) |
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$ GO TO 110 |
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IF( I.LT.J ) THEN |
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TMP = D( I ) |
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D( I ) = D( J ) |
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D( J ) = TMP |
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GO TO 90 |
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END IF |
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IF( J-START.GT.ENDD-J-1 ) THEN |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = START |
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STACK( 2, STKPNT ) = J |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = J + 1 |
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STACK( 2, STKPNT ) = ENDD |
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ELSE |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = J + 1 |
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STACK( 2, STKPNT ) = ENDD |
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STKPNT = STKPNT + 1 |
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STACK( 1, STKPNT ) = START |
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STACK( 2, STKPNT ) = J |
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END IF |
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END IF |
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END IF |
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IF( STKPNT.GT.0 ) |
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$ GO TO 10 |
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RETURN |
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* |
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* End of DLASRT |
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* |
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END |