* * SUBROUTINE DLASRT2( ID, N, D, KEY, INFO ) * * -- ScaLAPACK routine (version 1.5) -- * University of Tennessee, Knoxville, Oak Ridge National Laboratory, * and University of California, Berkeley. * May 1, 1997 * * .. Scalar Arguments .. CHARACTER ID INTEGER INFO, N * .. * .. Array Arguments .. INTEGER KEY( * ) DOUBLE PRECISION D( * ) * .. * * Purpose * ======= * * Sort the numbers in D in increasing order (if ID = 'I') or * in decreasing order (if ID = 'D' ). * * Use Quick Sort, reverting to Insertion sort on arrays of * size <= 20. Dimension of STACK limits N to about 2**32. * * Arguments * ========= * * ID (input) CHARACTER*1 * = 'I': sort D in increasing order; * = 'D': sort D in decreasing order. * * N (input) INTEGER * The length of the array D. * * D (input/output) DOUBLE PRECISION array, dimension (N) * On entry, the array to be sorted. * On exit, D has been sorted into increasing order * (D(1) <= ... <= D(N) ) or into decreasing order * (D(1) >= ... >= D(N) ), depending on ID. * * KEY (input/output) INTEGER array, dimension (N) * On entry, KEY contains a key to each of the entries in D() * Typically, KEY(I) = I for all I * On exit, KEY is permuted in exactly the same manner as * D() was permuted from input to output * Therefore, if KEY(I) = I for all I upon input, then * D_out(I) = D_in(KEY(I)) * * INFO (output) INTEGER * = 0: successful exit * < 0: if INFO = -i, the i-th argument had an illegal value * * ===================================================================== * * .. Parameters .. INTEGER SELECT PARAMETER ( SELECT = 20 ) * .. * .. Local Scalars .. INTEGER DIR, ENDD, I, J, START, STKPNT, TMPKEY DOUBLE PRECISION D1, D2, D3, DMNMX, TMP * .. * .. Local Arrays .. INTEGER STACK( 2, 32 ) * .. * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. * .. External Subroutines .. EXTERNAL XERBLA * .. * .. Executable Statements .. * * Test the input paramters. * * INFO = 0 DIR = -1 IF( LSAME( ID, 'D' ) ) THEN DIR = 0 ELSE IF( LSAME( ID, 'I' ) ) THEN DIR = 1 END IF IF( DIR.EQ.-1 ) THEN INFO = -1 ELSE IF( N.LT.0 ) THEN INFO = -2 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'DLASRT2', -INFO ) RETURN END IF * * Quick return if possible * IF( N.LE.1 ) $ RETURN * STKPNT = 1 STACK( 1, 1 ) = 1 STACK( 2, 1 ) = N 10 CONTINUE START = STACK( 1, STKPNT ) ENDD = STACK( 2, STKPNT ) STKPNT = STKPNT - 1 IF( ENDD-START.GT.0 ) THEN * * Do Insertion sort on D( START:ENDD ) * IF( DIR.EQ.0 ) THEN * * Sort into decreasing order * DO 30 I = START + 1, ENDD DO 20 J = I, START + 1, -1 IF( D( J ).GT.D( J-1 ) ) THEN DMNMX = D( J ) D( J ) = D( J-1 ) D( J-1 ) = DMNMX TMPKEY = KEY( J ) KEY( J ) = KEY( J-1 ) KEY( J-1 ) = TMPKEY ELSE GO TO 30 END IF 20 CONTINUE 30 CONTINUE * ELSE * * Sort into increasing order * DO 50 I = START + 1, ENDD DO 40 J = I, START + 1, -1 IF( D( J ).LT.D( J-1 ) ) THEN DMNMX = D( J ) D( J ) = D( J-1 ) D( J-1 ) = DMNMX TMPKEY = KEY( J ) KEY( J ) = KEY( J-1 ) KEY( J-1 ) = TMPKEY ELSE GO TO 50 END IF 40 CONTINUE 50 CONTINUE * END IF * ELSE IF( ENDD-START.GT.SELECT ) THEN * * Partition D( START:ENDD ) and stack parts, largest one first * * Choose partition entry as median of 3 * D1 = D( START ) D2 = D( ENDD ) I = ( START+ENDD ) / 2 D3 = D( I ) IF( D1.LT.D2 ) THEN IF( D3.LT.D1 ) THEN DMNMX = D1 ELSE IF( D3.LT.D2 ) THEN DMNMX = D3 ELSE DMNMX = D2 END IF ELSE IF( D3.LT.D2 ) THEN DMNMX = D2 ELSE IF( D3.LT.D1 ) THEN DMNMX = D3 ELSE DMNMX = D1 END IF END IF * IF( DIR.EQ.0 ) THEN * * Sort into decreasing order * I = START - 1 J = ENDD + 1 60 CONTINUE 70 CONTINUE J = J - 1 IF( D( J ).LT.DMNMX ) $ GO TO 70 80 CONTINUE I = I + 1 IF( D( I ).GT.DMNMX ) $ GO TO 80 IF( I.LT.J ) THEN TMP = D( I ) D( I ) = D( J ) D( J ) = TMP TMPKEY = KEY( J ) KEY( J ) = KEY( I ) KEY( I ) = TMPKEY GO TO 60 END IF IF( J-START.GT.ENDD-J-1 ) THEN STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = START STACK( 2, STKPNT ) = J STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = J + 1 STACK( 2, STKPNT ) = ENDD ELSE STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = J + 1 STACK( 2, STKPNT ) = ENDD STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = START STACK( 2, STKPNT ) = J END IF ELSE * * Sort into increasing order * I = START - 1 J = ENDD + 1 90 CONTINUE 100 CONTINUE J = J - 1 IF( D( J ).GT.DMNMX ) $ GO TO 100 110 CONTINUE I = I + 1 IF( D( I ).LT.DMNMX ) $ GO TO 110 IF( I.LT.J ) THEN TMP = D( I ) D( I ) = D( J ) D( J ) = TMP TMPKEY = KEY( J ) KEY( J ) = KEY( I ) KEY( I ) = TMPKEY GO TO 90 END IF IF( J-START.GT.ENDD-J-1 ) THEN STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = START STACK( 2, STKPNT ) = J STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = J + 1 STACK( 2, STKPNT ) = ENDD ELSE STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = J + 1 STACK( 2, STKPNT ) = ENDD STKPNT = STKPNT + 1 STACK( 1, STKPNT ) = START STACK( 2, STKPNT ) = J END IF END IF END IF IF( STKPNT.GT.0 ) $ GO TO 10 * * RETURN * * End of DLASRT2 * END