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Diffstat (limited to 'src/fortran/lapack/dlaqr4.f')
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diff --git a/src/fortran/lapack/dlaqr4.f b/src/fortran/lapack/dlaqr4.f new file mode 100644 index 0000000..8692e7f --- /dev/null +++ b/src/fortran/lapack/dlaqr4.f @@ -0,0 +1,640 @@ + SUBROUTINE DLAQR4( WANTT, WANTZ, N, ILO, IHI, H, LDH, WR, WI, + $ ILOZ, IHIZ, Z, LDZ, WORK, LWORK, INFO ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + INTEGER IHI, IHIZ, ILO, ILOZ, INFO, LDH, LDZ, LWORK, N + LOGICAL WANTT, WANTZ +* .. +* .. Array Arguments .. + DOUBLE PRECISION H( LDH, * ), WI( * ), WORK( * ), WR( * ), + $ Z( LDZ, * ) +* .. +* +* This subroutine implements one level of recursion for DLAQR0. +* It is a complete implementation of the small bulge multi-shift +* QR algorithm. It may be called by DLAQR0 and, for large enough +* deflation window size, it may be called by DLAQR3. This +* subroutine is identical to DLAQR0 except that it calls DLAQR2 +* instead of DLAQR3. +* +* Purpose +* ======= +* +* DLAQR4 computes the eigenvalues of a Hessenberg matrix H +* and, optionally, the matrices T and Z from the Schur decomposition +* H = Z T Z**T, where T is an upper quasi-triangular matrix (the +* Schur form), and Z is the orthogonal matrix of Schur vectors. +* +* Optionally Z may be postmultiplied into an input orthogonal +* matrix Q so that this routine can give the Schur factorization +* of a matrix A which has been reduced to the Hessenberg form H +* by the orthogonal matrix Q: A = Q*H*Q**T = (QZ)*T*(QZ)**T. +* +* Arguments +* ========= +* +* WANTT (input) LOGICAL +* = .TRUE. : the full Schur form T is required; +* = .FALSE.: only eigenvalues are required. +* +* WANTZ (input) LOGICAL +* = .TRUE. : the matrix of Schur vectors Z is required; +* = .FALSE.: Schur vectors are not required. +* +* N (input) INTEGER +* The order of the matrix H. N .GE. 0. +* +* ILO (input) INTEGER +* IHI (input) INTEGER +* It is assumed that H is already upper triangular in rows +* and columns 1:ILO-1 and IHI+1:N and, if ILO.GT.1, +* H(ILO,ILO-1) is zero. ILO and IHI are normally set by a +* previous call to DGEBAL, and then passed to DGEHRD when the +* matrix output by DGEBAL is reduced to Hessenberg form. +* Otherwise, ILO and IHI should be set to 1 and N, +* respectively. If N.GT.0, then 1.LE.ILO.LE.IHI.LE.N. +* If N = 0, then ILO = 1 and IHI = 0. +* +* H (input/output) DOUBLE PRECISION array, dimension (LDH,N) +* On entry, the upper Hessenberg matrix H. +* On exit, if INFO = 0 and WANTT is .TRUE., then H contains +* the upper quasi-triangular matrix T from the Schur +* decomposition (the Schur form); 2-by-2 diagonal blocks +* (corresponding to complex conjugate pairs of eigenvalues) +* are returned in standard form, with H(i,i) = H(i+1,i+1) +* and H(i+1,i)*H(i,i+1).LT.0. If INFO = 0 and WANTT is +* .FALSE., then the contents of H are unspecified on exit. +* (The output value of H when INFO.GT.0 is given under the +* description of INFO below.) +* +* This subroutine may explicitly set H(i,j) = 0 for i.GT.j and +* j = 1, 2, ... ILO-1 or j = IHI+1, IHI+2, ... N. +* +* LDH (input) INTEGER +* The leading dimension of the array H. LDH .GE. max(1,N). +* +* WR (output) DOUBLE PRECISION array, dimension (IHI) +* WI (output) DOUBLE PRECISION array, dimension (IHI) +* The real and imaginary parts, respectively, of the computed +* eigenvalues of H(ILO:IHI,ILO:IHI) are stored WR(ILO:IHI) +* and WI(ILO:IHI). If two eigenvalues are computed as a +* complex conjugate pair, they are stored in consecutive +* elements of WR and WI, say the i-th and (i+1)th, with +* WI(i) .GT. 0 and WI(i+1) .LT. 0. If WANTT is .TRUE., then +* the eigenvalues are stored in the same order as on the +* diagonal of the Schur form returned in H, with +* WR(i) = H(i,i) and, if H(i:i+1,i:i+1) is a 2-by-2 diagonal +* block, WI(i) = sqrt(-H(i+1,i)*H(i,i+1)) and +* WI(i+1) = -WI(i). +* +* ILOZ (input) INTEGER +* IHIZ (input) INTEGER +* Specify the rows of Z to which transformations must be +* applied if WANTZ is .TRUE.. +* 1 .LE. ILOZ .LE. ILO; IHI .LE. IHIZ .LE. N. +* +* Z (input/output) DOUBLE PRECISION array, dimension (LDZ,IHI) +* If WANTZ is .FALSE., then Z is not referenced. +* If WANTZ is .TRUE., then Z(ILO:IHI,ILOZ:IHIZ) is +* replaced by Z(ILO:IHI,ILOZ:IHIZ)*U where U is the +* orthogonal Schur factor of H(ILO:IHI,ILO:IHI). +* (The output value of Z when INFO.GT.0 is given under +* the description of INFO below.) +* +* LDZ (input) INTEGER +* The leading dimension of the array Z. if WANTZ is .TRUE. +* then LDZ.GE.MAX(1,IHIZ). Otherwize, LDZ.GE.1. +* +* WORK (workspace/output) DOUBLE PRECISION array, dimension LWORK +* On exit, if LWORK = -1, WORK(1) returns an estimate of +* the optimal value for LWORK. +* +* LWORK (input) INTEGER +* The dimension of the array WORK. LWORK .GE. max(1,N) +* is sufficient, but LWORK typically as large as 6*N may +* be required for optimal performance. A workspace query +* to determine the optimal workspace size is recommended. +* +* If LWORK = -1, then DLAQR4 does a workspace query. +* In this case, DLAQR4 checks the input parameters and +* estimates the optimal workspace size for the given +* values of N, ILO and IHI. The estimate is returned +* in WORK(1). No error message related to LWORK is +* issued by XERBLA. Neither H nor Z are accessed. +* +* +* INFO (output) INTEGER +* = 0: successful exit +* .GT. 0: if INFO = i, DLAQR4 failed to compute all of +* the eigenvalues. Elements 1:ilo-1 and i+1:n of WR +* and WI contain those eigenvalues which have been +* successfully computed. (Failures are rare.) +* +* If INFO .GT. 0 and WANT is .FALSE., then on exit, +* the remaining unconverged eigenvalues are the eigen- +* values of the upper Hessenberg matrix rows and +* columns ILO through INFO of the final, output +* value of H. +* +* If INFO .GT. 0 and WANTT is .TRUE., then on exit +* +* (*) (initial value of H)*U = U*(final value of H) +* +* where U is an orthogonal matrix. The final +* value of H is upper Hessenberg and quasi-triangular +* in rows and columns INFO+1 through IHI. +* +* If INFO .GT. 0 and WANTZ is .TRUE., then on exit +* +* (final value of Z(ILO:IHI,ILOZ:IHIZ) +* = (initial value of Z(ILO:IHI,ILOZ:IHIZ)*U +* +* where U is the orthogonal matrix in (*) (regard- +* less of the value of WANTT.) +* +* If INFO .GT. 0 and WANTZ is .FALSE., then Z is not +* accessed. +* +* ================================================================ +* Based on contributions by +* Karen Braman and Ralph Byers, Department of Mathematics, +* University of Kansas, USA +* +* ================================================================ +* References: +* K. Braman, R. Byers and R. Mathias, The Multi-Shift QR +* Algorithm Part I: Maintaining Well Focused Shifts, and Level 3 +* Performance, SIAM Journal of Matrix Analysis, volume 23, pages +* 929--947, 2002. +* +* K. Braman, R. Byers and R. Mathias, The Multi-Shift QR +* Algorithm Part II: Aggressive Early Deflation, SIAM Journal +* of Matrix Analysis, volume 23, pages 948--973, 2002. +* +* ================================================================ +* .. Parameters .. +* +* ==== Matrices of order NTINY or smaller must be processed by +* . DLAHQR because of insufficient subdiagonal scratch space. +* . (This is a hard limit.) ==== +* +* ==== Exceptional deflation windows: try to cure rare +* . slow convergence by increasing the size of the +* . deflation window after KEXNW iterations. ===== +* +* ==== Exceptional shifts: try to cure rare slow convergence +* . with ad-hoc exceptional shifts every KEXSH iterations. +* . The constants WILK1 and WILK2 are used to form the +* . exceptional shifts. ==== +* + INTEGER NTINY + PARAMETER ( NTINY = 11 ) + INTEGER KEXNW, KEXSH + PARAMETER ( KEXNW = 5, KEXSH = 6 ) + DOUBLE PRECISION WILK1, WILK2 + PARAMETER ( WILK1 = 0.75d0, WILK2 = -0.4375d0 ) + DOUBLE PRECISION ZERO, ONE + PARAMETER ( ZERO = 0.0d0, ONE = 1.0d0 ) +* .. +* .. Local Scalars .. + DOUBLE PRECISION AA, BB, CC, CS, DD, SN, SS, SWAP + INTEGER I, INF, IT, ITMAX, K, KACC22, KBOT, KDU, KS, + $ KT, KTOP, KU, KV, KWH, KWTOP, KWV, LD, LS, + $ LWKOPT, NDFL, NH, NHO, NIBBLE, NMIN, NS, NSMAX, + $ NSR, NVE, NW, NWMAX, NWR + LOGICAL NWINC, SORTED + CHARACTER JBCMPZ*2 +* .. +* .. External Functions .. + INTEGER ILAENV + EXTERNAL ILAENV +* .. +* .. Local Arrays .. + DOUBLE PRECISION ZDUM( 1, 1 ) +* .. +* .. External Subroutines .. + EXTERNAL DLACPY, DLAHQR, DLANV2, DLAQR2, DLAQR5 +* .. +* .. Intrinsic Functions .. + INTRINSIC ABS, DBLE, INT, MAX, MIN, MOD +* .. +* .. Executable Statements .. + INFO = 0 +* +* ==== Quick return for N = 0: nothing to do. ==== +* + IF( N.EQ.0 ) THEN + WORK( 1 ) = ONE + RETURN + END IF +* +* ==== Set up job flags for ILAENV. ==== +* + IF( WANTT ) THEN + JBCMPZ( 1: 1 ) = 'S' + ELSE + JBCMPZ( 1: 1 ) = 'E' + END IF + IF( WANTZ ) THEN + JBCMPZ( 2: 2 ) = 'V' + ELSE + JBCMPZ( 2: 2 ) = 'N' + END IF +* +* ==== Tiny matrices must use DLAHQR. ==== +* + IF( N.LE.NTINY ) THEN +* +* ==== Estimate optimal workspace. ==== +* + LWKOPT = 1 + IF( LWORK.NE.-1 ) + $ CALL DLAHQR( WANTT, WANTZ, N, ILO, IHI, H, LDH, WR, WI, + $ ILOZ, IHIZ, Z, LDZ, INFO ) + ELSE +* +* ==== Use small bulge multi-shift QR with aggressive early +* . deflation on larger-than-tiny matrices. ==== +* +* ==== Hope for the best. ==== +* + INFO = 0 +* +* ==== NWR = recommended deflation window size. At this +* . point, N .GT. NTINY = 11, so there is enough +* . subdiagonal workspace for NWR.GE.2 as required. +* . (In fact, there is enough subdiagonal space for +* . NWR.GE.3.) ==== +* + NWR = ILAENV( 13, 'DLAQR4', JBCMPZ, N, ILO, IHI, LWORK ) + NWR = MAX( 2, NWR ) + NWR = MIN( IHI-ILO+1, ( N-1 ) / 3, NWR ) + NW = NWR +* +* ==== NSR = recommended number of simultaneous shifts. +* . At this point N .GT. NTINY = 11, so there is at +* . enough subdiagonal workspace for NSR to be even +* . and greater than or equal to two as required. ==== +* + NSR = ILAENV( 15, 'DLAQR4', JBCMPZ, N, ILO, IHI, LWORK ) + NSR = MIN( NSR, ( N+6 ) / 9, IHI-ILO ) + NSR = MAX( 2, NSR-MOD( NSR, 2 ) ) +* +* ==== Estimate optimal workspace ==== +* +* ==== Workspace query call to DLAQR2 ==== +* + CALL DLAQR2( WANTT, WANTZ, N, ILO, IHI, NWR+1, H, LDH, ILOZ, + $ IHIZ, Z, LDZ, LS, LD, WR, WI, H, LDH, N, H, LDH, + $ N, H, LDH, WORK, -1 ) +* +* ==== Optimal workspace = MAX(DLAQR5, DLAQR2) ==== +* + LWKOPT = MAX( 3*NSR / 2, INT( WORK( 1 ) ) ) +* +* ==== Quick return in case of workspace query. ==== +* + IF( LWORK.EQ.-1 ) THEN + WORK( 1 ) = DBLE( LWKOPT ) + RETURN + END IF +* +* ==== DLAHQR/DLAQR0 crossover point ==== +* + NMIN = ILAENV( 12, 'DLAQR4', JBCMPZ, N, ILO, IHI, LWORK ) + NMIN = MAX( NTINY, NMIN ) +* +* ==== Nibble crossover point ==== +* + NIBBLE = ILAENV( 14, 'DLAQR4', JBCMPZ, N, ILO, IHI, LWORK ) + NIBBLE = MAX( 0, NIBBLE ) +* +* ==== Accumulate reflections during ttswp? Use block +* . 2-by-2 structure during matrix-matrix multiply? ==== +* + KACC22 = ILAENV( 16, 'DLAQR4', JBCMPZ, N, ILO, IHI, LWORK ) + KACC22 = MAX( 0, KACC22 ) + KACC22 = MIN( 2, KACC22 ) +* +* ==== NWMAX = the largest possible deflation window for +* . which there is sufficient workspace. ==== +* + NWMAX = MIN( ( N-1 ) / 3, LWORK / 2 ) +* +* ==== NSMAX = the Largest number of simultaneous shifts +* . for which there is sufficient workspace. ==== +* + NSMAX = MIN( ( N+6 ) / 9, 2*LWORK / 3 ) + NSMAX = NSMAX - MOD( NSMAX, 2 ) +* +* ==== NDFL: an iteration count restarted at deflation. ==== +* + NDFL = 1 +* +* ==== ITMAX = iteration limit ==== +* + ITMAX = MAX( 30, 2*KEXSH )*MAX( 10, ( IHI-ILO+1 ) ) +* +* ==== Last row and column in the active block ==== +* + KBOT = IHI +* +* ==== Main Loop ==== +* + DO 80 IT = 1, ITMAX +* +* ==== Done when KBOT falls below ILO ==== +* + IF( KBOT.LT.ILO ) + $ GO TO 90 +* +* ==== Locate active block ==== +* + DO 10 K = KBOT, ILO + 1, -1 + IF( H( K, K-1 ).EQ.ZERO ) + $ GO TO 20 + 10 CONTINUE + K = ILO + 20 CONTINUE + KTOP = K +* +* ==== Select deflation window size ==== +* + NH = KBOT - KTOP + 1 + IF( NDFL.LT.KEXNW .OR. NH.LT.NW ) THEN +* +* ==== Typical deflation window. If possible and +* . advisable, nibble the entire active block. +* . If not, use size NWR or NWR+1 depending upon +* . which has the smaller corresponding subdiagonal +* . entry (a heuristic). ==== +* + NWINC = .TRUE. + IF( NH.LE.MIN( NMIN, NWMAX ) ) THEN + NW = NH + ELSE + NW = MIN( NWR, NH, NWMAX ) + IF( NW.LT.NWMAX ) THEN + IF( NW.GE.NH-1 ) THEN + NW = NH + ELSE + KWTOP = KBOT - NW + 1 + IF( ABS( H( KWTOP, KWTOP-1 ) ).GT. + $ ABS( H( KWTOP-1, KWTOP-2 ) ) )NW = NW + 1 + END IF + END IF + END IF + ELSE +* +* ==== Exceptional deflation window. If there have +* . been no deflations in KEXNW or more iterations, +* . then vary the deflation window size. At first, +* . because, larger windows are, in general, more +* . powerful than smaller ones, rapidly increase the +* . window up to the maximum reasonable and possible. +* . Then maybe try a slightly smaller window. ==== +* + IF( NWINC .AND. NW.LT.MIN( NWMAX, NH ) ) THEN + NW = MIN( NWMAX, NH, 2*NW ) + ELSE + NWINC = .FALSE. + IF( NW.EQ.NH .AND. NH.GT.2 ) + $ NW = NH - 1 + END IF + END IF +* +* ==== Aggressive early deflation: +* . split workspace under the subdiagonal into +* . - an nw-by-nw work array V in the lower +* . left-hand-corner, +* . - an NW-by-at-least-NW-but-more-is-better +* . (NW-by-NHO) horizontal work array along +* . the bottom edge, +* . - an at-least-NW-but-more-is-better (NHV-by-NW) +* . vertical work array along the left-hand-edge. +* . ==== +* + KV = N - NW + 1 + KT = NW + 1 + NHO = ( N-NW-1 ) - KT + 1 + KWV = NW + 2 + NVE = ( N-NW ) - KWV + 1 +* +* ==== Aggressive early deflation ==== +* + CALL DLAQR2( WANTT, WANTZ, N, KTOP, KBOT, NW, H, LDH, ILOZ, + $ IHIZ, Z, LDZ, LS, LD, WR, WI, H( KV, 1 ), LDH, + $ NHO, H( KV, KT ), LDH, NVE, H( KWV, 1 ), LDH, + $ WORK, LWORK ) +* +* ==== Adjust KBOT accounting for new deflations. ==== +* + KBOT = KBOT - LD +* +* ==== KS points to the shifts. ==== +* + KS = KBOT - LS + 1 +* +* ==== Skip an expensive QR sweep if there is a (partly +* . heuristic) reason to expect that many eigenvalues +* . will deflate without it. Here, the QR sweep is +* . skipped if many eigenvalues have just been deflated +* . or if the remaining active block is small. +* + IF( ( LD.EQ.0 ) .OR. ( ( 100*LD.LE.NW*NIBBLE ) .AND. ( KBOT- + $ KTOP+1.GT.MIN( NMIN, NWMAX ) ) ) ) THEN +* +* ==== NS = nominal number of simultaneous shifts. +* . This may be lowered (slightly) if DLAQR2 +* . did not provide that many shifts. ==== +* + NS = MIN( NSMAX, NSR, MAX( 2, KBOT-KTOP ) ) + NS = NS - MOD( NS, 2 ) +* +* ==== If there have been no deflations +* . in a multiple of KEXSH iterations, +* . then try exceptional shifts. +* . Otherwise use shifts provided by +* . DLAQR2 above or from the eigenvalues +* . of a trailing principal submatrix. ==== +* + IF( MOD( NDFL, KEXSH ).EQ.0 ) THEN + KS = KBOT - NS + 1 + DO 30 I = KBOT, MAX( KS+1, KTOP+2 ), -2 + SS = ABS( H( I, I-1 ) ) + ABS( H( I-1, I-2 ) ) + AA = WILK1*SS + H( I, I ) + BB = SS + CC = WILK2*SS + DD = AA + CALL DLANV2( AA, BB, CC, DD, WR( I-1 ), WI( I-1 ), + $ WR( I ), WI( I ), CS, SN ) + 30 CONTINUE + IF( KS.EQ.KTOP ) THEN + WR( KS+1 ) = H( KS+1, KS+1 ) + WI( KS+1 ) = ZERO + WR( KS ) = WR( KS+1 ) + WI( KS ) = WI( KS+1 ) + END IF + ELSE +* +* ==== Got NS/2 or fewer shifts? Use DLAHQR +* . on a trailing principal submatrix to +* . get more. (Since NS.LE.NSMAX.LE.(N+6)/9, +* . there is enough space below the subdiagonal +* . to fit an NS-by-NS scratch array.) ==== +* + IF( KBOT-KS+1.LE.NS / 2 ) THEN + KS = KBOT - NS + 1 + KT = N - NS + 1 + CALL DLACPY( 'A', NS, NS, H( KS, KS ), LDH, + $ H( KT, 1 ), LDH ) + CALL DLAHQR( .false., .false., NS, 1, NS, + $ H( KT, 1 ), LDH, WR( KS ), WI( KS ), + $ 1, 1, ZDUM, 1, INF ) + KS = KS + INF +* +* ==== In case of a rare QR failure use +* . eigenvalues of the trailing 2-by-2 +* . principal submatrix. ==== +* + IF( KS.GE.KBOT ) THEN + AA = H( KBOT-1, KBOT-1 ) + CC = H( KBOT, KBOT-1 ) + BB = H( KBOT-1, KBOT ) + DD = H( KBOT, KBOT ) + CALL DLANV2( AA, BB, CC, DD, WR( KBOT-1 ), + $ WI( KBOT-1 ), WR( KBOT ), + $ WI( KBOT ), CS, SN ) + KS = KBOT - 1 + END IF + END IF +* + IF( KBOT-KS+1.GT.NS ) THEN +* +* ==== Sort the shifts (Helps a little) +* . Bubble sort keeps complex conjugate +* . pairs together. ==== +* + SORTED = .false. + DO 50 K = KBOT, KS + 1, -1 + IF( SORTED ) + $ GO TO 60 + SORTED = .true. + DO 40 I = KS, K - 1 + IF( ABS( WR( I ) )+ABS( WI( I ) ).LT. + $ ABS( WR( I+1 ) )+ABS( WI( I+1 ) ) ) THEN + SORTED = .false. +* + SWAP = WR( I ) + WR( I ) = WR( I+1 ) + WR( I+1 ) = SWAP +* + SWAP = WI( I ) + WI( I ) = WI( I+1 ) + WI( I+1 ) = SWAP + END IF + 40 CONTINUE + 50 CONTINUE + 60 CONTINUE + END IF +* +* ==== Shuffle shifts into pairs of real shifts +* . and pairs of complex conjugate shifts +* . assuming complex conjugate shifts are +* . already adjacent to one another. (Yes, +* . they are.) ==== +* + DO 70 I = KBOT, KS + 2, -2 + IF( WI( I ).NE.-WI( I-1 ) ) THEN +* + SWAP = WR( I ) + WR( I ) = WR( I-1 ) + WR( I-1 ) = WR( I-2 ) + WR( I-2 ) = SWAP +* + SWAP = WI( I ) + WI( I ) = WI( I-1 ) + WI( I-1 ) = WI( I-2 ) + WI( I-2 ) = SWAP + END IF + 70 CONTINUE + END IF +* +* ==== If there are only two shifts and both are +* . real, then use only one. ==== +* + IF( KBOT-KS+1.EQ.2 ) THEN + IF( WI( KBOT ).EQ.ZERO ) THEN + IF( ABS( WR( KBOT )-H( KBOT, KBOT ) ).LT. + $ ABS( WR( KBOT-1 )-H( KBOT, KBOT ) ) ) THEN + WR( KBOT-1 ) = WR( KBOT ) + ELSE + WR( KBOT ) = WR( KBOT-1 ) + END IF + END IF + END IF +* +* ==== Use up to NS of the the smallest magnatiude +* . shifts. If there aren't NS shifts available, +* . then use them all, possibly dropping one to +* . make the number of shifts even. ==== +* + NS = MIN( NS, KBOT-KS+1 ) + NS = NS - MOD( NS, 2 ) + KS = KBOT - NS + 1 +* +* ==== Small-bulge multi-shift QR sweep: +* . split workspace under the subdiagonal into +* . - a KDU-by-KDU work array U in the lower +* . left-hand-corner, +* . - a KDU-by-at-least-KDU-but-more-is-better +* . (KDU-by-NHo) horizontal work array WH along +* . the bottom edge, +* . - and an at-least-KDU-but-more-is-better-by-KDU +* . (NVE-by-KDU) vertical work WV arrow along +* . the left-hand-edge. ==== +* + KDU = 3*NS - 3 + KU = N - KDU + 1 + KWH = KDU + 1 + NHO = ( N-KDU+1-4 ) - ( KDU+1 ) + 1 + KWV = KDU + 4 + NVE = N - KDU - KWV + 1 +* +* ==== Small-bulge multi-shift QR sweep ==== +* + CALL DLAQR5( WANTT, WANTZ, KACC22, N, KTOP, KBOT, NS, + $ WR( KS ), WI( KS ), H, LDH, ILOZ, IHIZ, Z, + $ LDZ, WORK, 3, H( KU, 1 ), LDH, NVE, + $ H( KWV, 1 ), LDH, NHO, H( KU, KWH ), LDH ) + END IF +* +* ==== Note progress (or the lack of it). ==== +* + IF( LD.GT.0 ) THEN + NDFL = 1 + ELSE + NDFL = NDFL + 1 + END IF +* +* ==== End of main loop ==== + 80 CONTINUE +* +* ==== Iteration limit exceeded. Set INFO to show where +* . the problem occurred and exit. ==== +* + INFO = KBOT + 90 CONTINUE + END IF +* +* ==== Return the optimal value of LWORK. ==== +* + WORK( 1 ) = DBLE( LWKOPT ) +* +* ==== End of DLAQR4 ==== +* + END |