#include "f2c.h" #include "blaswrap.h" /* Table of constant values */ static integer c__1 = 1; static doublereal c_b36 = .5; /* Subroutine */ int zlatbs_(char *uplo, char *trans, char *diag, char * normin, integer *n, integer *kd, doublecomplex *ab, integer *ldab, doublecomplex *x, doublereal *scale, doublereal *cnorm, integer *info) { /* System generated locals */ integer ab_dim1, ab_offset, i__1, i__2, i__3, i__4, i__5; doublereal d__1, d__2, d__3, d__4; doublecomplex z__1, z__2, z__3, z__4; /* Builtin functions */ double d_imag(doublecomplex *); void d_cnjg(doublecomplex *, doublecomplex *); /* Local variables */ integer i__, j; doublereal xj, rec, tjj; integer jinc, jlen; doublereal xbnd; integer imax; doublereal tmax; doublecomplex tjjs; doublereal xmax, grow; extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *, integer *); integer maind; extern logical lsame_(char *, char *); doublereal tscal; doublecomplex uscal; integer jlast; doublecomplex csumj; extern /* Double Complex */ VOID zdotc_(doublecomplex *, integer *, doublecomplex *, integer *, doublecomplex *, integer *); logical upper; extern /* Double Complex */ VOID zdotu_(doublecomplex *, integer *, doublecomplex *, integer *, doublecomplex *, integer *); extern /* Subroutine */ int ztbsv_(char *, char *, char *, integer *, integer *, doublecomplex *, integer *, doublecomplex *, integer *), zaxpy_(integer *, doublecomplex *, doublecomplex *, integer *, doublecomplex *, integer *), dlabad_( doublereal *, doublereal *); extern doublereal dlamch_(char *); extern integer idamax_(integer *, doublereal *, integer *); extern /* Subroutine */ int xerbla_(char *, integer *), zdscal_( integer *, doublereal *, doublecomplex *, integer *); doublereal bignum; extern integer izamax_(integer *, doublecomplex *, integer *); extern /* Double Complex */ VOID zladiv_(doublecomplex *, doublecomplex *, doublecomplex *); logical notran; integer jfirst; extern doublereal dzasum_(integer *, doublecomplex *, integer *); doublereal smlnum; logical nounit; /* -- LAPACK auxiliary routine (version 3.1) -- */ /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ /* November 2006 */ /* .. Scalar Arguments .. */ /* .. */ /* .. Array Arguments .. */ /* .. */ /* Purpose */ /* ======= */ /* ZLATBS solves one of the triangular systems */ /* A * x = s*b, A**T * x = s*b, or A**H * x = s*b, */ /* with scaling to prevent overflow, where A is an upper or lower */ /* triangular band matrix. Here A' denotes the transpose of A, x and b */ /* are n-element vectors, and s is a scaling factor, usually less than */ /* or equal to 1, chosen so that the components of x will be less than */ /* the overflow threshold. If the unscaled problem will not cause */ /* overflow, the Level 2 BLAS routine ZTBSV is called. If the matrix A */ /* is singular (A(j,j) = 0 for some j), then s is set to 0 and a */ /* non-trivial solution to A*x = 0 is returned. */ /* Arguments */ /* ========= */ /* UPLO (input) CHARACTER*1 */ /* Specifies whether the matrix A is upper or lower triangular. */ /* = 'U': Upper triangular */ /* = 'L': Lower triangular */ /* TRANS (input) CHARACTER*1 */ /* Specifies the operation applied to A. */ /* = 'N': Solve A * x = s*b (No transpose) */ /* = 'T': Solve A**T * x = s*b (Transpose) */ /* = 'C': Solve A**H * x = s*b (Conjugate transpose) */ /* DIAG (input) CHARACTER*1 */ /* Specifies whether or not the matrix A is unit triangular. */ /* = 'N': Non-unit triangular */ /* = 'U': Unit triangular */ /* NORMIN (input) CHARACTER*1 */ /* Specifies whether CNORM has been set or not. */ /* = 'Y': CNORM contains the column norms on entry */ /* = 'N': CNORM is not set on entry. On exit, the norms will */ /* be computed and stored in CNORM. */ /* N (input) INTEGER */ /* The order of the matrix A. N >= 0. */ /* KD (input) INTEGER */ /* The number of subdiagonals or superdiagonals in the */ /* triangular matrix A. KD >= 0. */ /* AB (input) COMPLEX*16 array, dimension (LDAB,N) */ /* The upper or lower triangular band matrix A, stored in the */ /* first KD+1 rows of the array. The j-th column of A is stored */ /* in the j-th column of the array AB as follows: */ /* if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; */ /* if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd). */ /* LDAB (input) INTEGER */ /* The leading dimension of the array AB. LDAB >= KD+1. */ /* X (input/output) COMPLEX*16 array, dimension (N) */ /* On entry, the right hand side b of the triangular system. */ /* On exit, X is overwritten by the solution vector x. */ /* SCALE (output) DOUBLE PRECISION */ /* The scaling factor s for the triangular system */ /* A * x = s*b, A**T * x = s*b, or A**H * x = s*b. */ /* If SCALE = 0, the matrix A is singular or badly scaled, and */ /* the vector x is an exact or approximate solution to A*x = 0. */ /* CNORM (input or output) DOUBLE PRECISION array, dimension (N) */ /* If NORMIN = 'Y', CNORM is an input argument and CNORM(j) */ /* contains the norm of the off-diagonal part of the j-th column */ /* of A. If TRANS = 'N', CNORM(j) must be greater than or equal */ /* to the infinity-norm, and if TRANS = 'T' or 'C', CNORM(j) */ /* must be greater than or equal to the 1-norm. */ /* If NORMIN = 'N', CNORM is an output argument and CNORM(j) */ /* returns the 1-norm of the offdiagonal part of the j-th column */ /* of A. */ /* INFO (output) INTEGER */ /* = 0: successful exit */ /* < 0: if INFO = -k, the k-th argument had an illegal value */ /* Further Details */ /* ======= ======= */ /* A rough bound on x is computed; if that is less than overflow, ZTBSV */ /* is called, otherwise, specific code is used which checks for possible */ /* overflow or divide-by-zero at every operation. */ /* A columnwise scheme is used for solving A*x = b. The basic algorithm */ /* if A is lower triangular is */ /* x[1:n] := b[1:n] */ /* for j = 1, ..., n */ /* x(j) := x(j) / A(j,j) */ /* x[j+1:n] := x[j+1:n] - x(j) * A[j+1:n,j] */ /* end */ /* Define bounds on the components of x after j iterations of the loop: */ /* M(j) = bound on x[1:j] */ /* G(j) = bound on x[j+1:n] */ /* Initially, let M(0) = 0 and G(0) = max{x(i), i=1,...,n}. */ /* Then for iteration j+1 we have */ /* M(j+1) <= G(j) / | A(j+1,j+1) | */ /* G(j+1) <= G(j) + M(j+1) * | A[j+2:n,j+1] | */ /* <= G(j) ( 1 + CNORM(j+1) / | A(j+1,j+1) | ) */ /* where CNORM(j+1) is greater than or equal to the infinity-norm of */ /* column j+1 of A, not counting the diagonal. Hence */ /* G(j) <= G(0) product ( 1 + CNORM(i) / | A(i,i) | ) */ /* 1<=i<=j */ /* and */ /* |x(j)| <= ( G(0) / |A(j,j)| ) product ( 1 + CNORM(i) / |A(i,i)| ) */ /* 1<=i< j */ /* Since |x(j)| <= M(j), we use the Level 2 BLAS routine ZTBSV if the */ /* reciprocal of the largest M(j), j=1,..,n, is larger than */ /* max(underflow, 1/overflow). */ /* The bound on x(j) is also used to determine when a step in the */ /* columnwise method can be performed without fear of overflow. If */ /* the computed bound is greater than a large constant, x is scaled to */ /* prevent overflow, but if the bound overflows, x is set to 0, x(j) to */ /* 1, and scale to 0, and a non-trivial solution to A*x = 0 is found. */ /* Similarly, a row-wise scheme is used to solve A**T *x = b or */ /* A**H *x = b. The basic algorithm for A upper triangular is */ /* for j = 1, ..., n */ /* x(j) := ( b(j) - A[1:j-1,j]' * x[1:j-1] ) / A(j,j) */ /* end */ /* We simultaneously compute two bounds */ /* G(j) = bound on ( b(i) - A[1:i-1,i]' * x[1:i-1] ), 1<=i<=j */ /* M(j) = bound on x(i), 1<=i<=j */ /* The initial values are G(0) = 0, M(0) = max{b(i), i=1,..,n}, and we */ /* add the constraint G(j) >= G(j-1) and M(j) >= M(j-1) for j >= 1. */ /* Then the bound on x(j) is */ /* M(j) <= M(j-1) * ( 1 + CNORM(j) ) / | A(j,j) | */ /* <= M(0) * product ( ( 1 + CNORM(i) ) / |A(i,i)| ) */ /* 1<=i<=j */ /* and we can safely call ZTBSV if 1/M(n) and 1/G(n) are both greater */ /* than max(underflow, 1/overflow). */ /* ===================================================================== */ /* .. Parameters .. */ /* .. */ /* .. Local Scalars .. */ /* .. */ /* .. External Functions .. */ /* .. */ /* .. External Subroutines .. */ /* .. */ /* .. Intrinsic Functions .. */ /* .. */ /* .. Statement Functions .. */ /* .. */ /* .. Statement Function definitions .. */ /* .. */ /* .. Executable Statements .. */ /* Parameter adjustments */ ab_dim1 = *ldab; ab_offset = 1 + ab_dim1; ab -= ab_offset; --x; --cnorm; /* Function Body */ *info = 0; upper = lsame_(uplo, "U"); notran = lsame_(trans, "N"); nounit = lsame_(diag, "N"); /* Test the input parameters. */ if (! upper && ! lsame_(uplo, "L")) { *info = -1; } else if (! notran && ! lsame_(trans, "T") && ! lsame_(trans, "C")) { *info = -2; } else if (! nounit && ! lsame_(diag, "U")) { *info = -3; } else if (! lsame_(normin, "Y") && ! lsame_(normin, "N")) { *info = -4; } else if (*n < 0) { *info = -5; } else if (*kd < 0) { *info = -6; } else if (*ldab < *kd + 1) { *info = -8; } if (*info != 0) { i__1 = -(*info); xerbla_("ZLATBS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0) { return 0; } /* Determine machine dependent parameters to control overflow. */ smlnum = dlamch_("Safe minimum"); bignum = 1. / smlnum; dlabad_(&smlnum, &bignum); smlnum /= dlamch_("Precision"); bignum = 1. / smlnum; *scale = 1.; if (lsame_(normin, "N")) { /* Compute the 1-norm of each column, not including the diagonal. */ if (upper) { /* A is upper triangular. */ i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MIN */ i__2 = *kd, i__3 = j - 1; jlen = min(i__2,i__3); cnorm[j] = dzasum_(&jlen, &ab[*kd + 1 - jlen + j * ab_dim1], & c__1); /* L10: */ } } else { /* A is lower triangular. */ i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MIN */ i__2 = *kd, i__3 = *n - j; jlen = min(i__2,i__3); if (jlen > 0) { cnorm[j] = dzasum_(&jlen, &ab[j * ab_dim1 + 2], &c__1); } else { cnorm[j] = 0.; } /* L20: */ } } } /* Scale the column norms by TSCAL if the maximum element in CNORM is */ /* greater than BIGNUM/2. */ imax = idamax_(n, &cnorm[1], &c__1); tmax = cnorm[imax]; if (tmax <= bignum * .5) { tscal = 1.; } else { tscal = .5 / (smlnum * tmax); dscal_(n, &tscal, &cnorm[1], &c__1); } /* Compute a bound on the computed solution vector to see if the */ /* Level 2 BLAS routine ZTBSV can be used. */ xmax = 0.; i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MAX */ i__2 = j; d__3 = xmax, d__4 = (d__1 = x[i__2].r / 2., abs(d__1)) + (d__2 = d_imag(&x[j]) / 2., abs(d__2)); xmax = max(d__3,d__4); /* L30: */ } xbnd = xmax; if (notran) { /* Compute the growth in A * x = b. */ if (upper) { jfirst = *n; jlast = 1; jinc = -1; maind = *kd + 1; } else { jfirst = 1; jlast = *n; jinc = 1; maind = 1; } if (tscal != 1.) { grow = 0.; goto L60; } if (nounit) { /* A is non-unit triangular. */ /* Compute GROW = 1/G(j) and XBND = 1/M(j). */ /* Initially, G(0) = max{x(i), i=1,...,n}. */ grow = .5 / max(xbnd,smlnum); xbnd = grow; i__1 = jlast; i__2 = jinc; for (j = jfirst; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) { /* Exit the loop if the growth factor is too small. */ if (grow <= smlnum) { goto L60; } i__3 = maind + j * ab_dim1; tjjs.r = ab[i__3].r, tjjs.i = ab[i__3].i; tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs( d__2)); if (tjj >= smlnum) { /* M(j) = G(j-1) / abs(A(j,j)) */ /* Computing MIN */ d__1 = xbnd, d__2 = min(1.,tjj) * grow; xbnd = min(d__1,d__2); } else { /* M(j) could overflow, set XBND to 0. */ xbnd = 0.; } if (tjj + cnorm[j] >= smlnum) { /* G(j) = G(j-1)*( 1 + CNORM(j) / abs(A(j,j)) ) */ grow *= tjj / (tjj + cnorm[j]); } else { /* G(j) could overflow, set GROW to 0. */ grow = 0.; } /* L40: */ } grow = xbnd; } else { /* A is unit triangular. */ /* Compute GROW = 1/G(j), where G(0) = max{x(i), i=1,...,n}. */ /* Computing MIN */ d__1 = 1., d__2 = .5 / max(xbnd,smlnum); grow = min(d__1,d__2); i__2 = jlast; i__1 = jinc; for (j = jfirst; i__1 < 0 ? j >= i__2 : j <= i__2; j += i__1) { /* Exit the loop if the growth factor is too small. */ if (grow <= smlnum) { goto L60; } /* G(j) = G(j-1)*( 1 + CNORM(j) ) */ grow *= 1. / (cnorm[j] + 1.); /* L50: */ } } L60: ; } else { /* Compute the growth in A**T * x = b or A**H * x = b. */ if (upper) { jfirst = 1; jlast = *n; jinc = 1; maind = *kd + 1; } else { jfirst = *n; jlast = 1; jinc = -1; maind = 1; } if (tscal != 1.) { grow = 0.; goto L90; } if (nounit) { /* A is non-unit triangular. */ /* Compute GROW = 1/G(j) and XBND = 1/M(j). */ /* Initially, M(0) = max{x(i), i=1,...,n}. */ grow = .5 / max(xbnd,smlnum); xbnd = grow; i__1 = jlast; i__2 = jinc; for (j = jfirst; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) { /* Exit the loop if the growth factor is too small. */ if (grow <= smlnum) { goto L90; } /* G(j) = max( G(j-1), M(j-1)*( 1 + CNORM(j) ) ) */ xj = cnorm[j] + 1.; /* Computing MIN */ d__1 = grow, d__2 = xbnd / xj; grow = min(d__1,d__2); i__3 = maind + j * ab_dim1; tjjs.r = ab[i__3].r, tjjs.i = ab[i__3].i; tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs( d__2)); if (tjj >= smlnum) { /* M(j) = M(j-1)*( 1 + CNORM(j) ) / abs(A(j,j)) */ if (xj > tjj) { xbnd *= tjj / xj; } } else { /* M(j) could overflow, set XBND to 0. */ xbnd = 0.; } /* L70: */ } grow = min(grow,xbnd); } else { /* A is unit triangular. */ /* Compute GROW = 1/G(j), where G(0) = max{x(i), i=1,...,n}. */ /* Computing MIN */ d__1 = 1., d__2 = .5 / max(xbnd,smlnum); grow = min(d__1,d__2); i__2 = jlast; i__1 = jinc; for (j = jfirst; i__1 < 0 ? j >= i__2 : j <= i__2; j += i__1) { /* Exit the loop if the growth factor is too small. */ if (grow <= smlnum) { goto L90; } /* G(j) = ( 1 + CNORM(j) )*G(j-1) */ xj = cnorm[j] + 1.; grow /= xj; /* L80: */ } } L90: ; } if (grow * tscal > smlnum) { /* Use the Level 2 BLAS solve if the reciprocal of the bound on */ /* elements of X is not too small. */ ztbsv_(uplo, trans, diag, n, kd, &ab[ab_offset], ldab, &x[1], &c__1); } else { /* Use a Level 1 BLAS solve, scaling intermediate results. */ if (xmax > bignum * .5) { /* Scale X so that its components are less than or equal to */ /* BIGNUM in absolute value. */ *scale = bignum * .5 / xmax; zdscal_(n, scale, &x[1], &c__1); xmax = bignum; } else { xmax *= 2.; } if (notran) { /* Solve A * x = b */ i__1 = jlast; i__2 = jinc; for (j = jfirst; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) { /* Compute x(j) = b(j) / A(j,j), scaling x if necessary. */ i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]), abs(d__2)); if (nounit) { i__3 = maind + j * ab_dim1; z__1.r = tscal * ab[i__3].r, z__1.i = tscal * ab[i__3].i; tjjs.r = z__1.r, tjjs.i = z__1.i; } else { tjjs.r = tscal, tjjs.i = 0.; if (tscal == 1.) { goto L110; } } tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs( d__2)); if (tjj > smlnum) { /* abs(A(j,j)) > SMLNUM: */ if (tjj < 1.) { if (xj > tjj * bignum) { /* Scale x by 1/b(j). */ rec = 1. / xj; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]) , abs(d__2)); } else if (tjj > 0.) { /* 0 < abs(A(j,j)) <= SMLNUM: */ if (xj > tjj * bignum) { /* Scale x by (1/abs(x(j)))*abs(A(j,j))*BIGNUM */ /* to avoid overflow when dividing by A(j,j). */ rec = tjj * bignum / xj; if (cnorm[j] > 1.) { /* Scale by 1/CNORM(j) to avoid overflow when */ /* multiplying x(j) times column j. */ rec /= cnorm[j]; } zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]) , abs(d__2)); } else { /* A(j,j) = 0: Set x(1:n) = 0, x(j) = 1, and */ /* scale = 0, and compute a solution to A*x = 0. */ i__3 = *n; for (i__ = 1; i__ <= i__3; ++i__) { i__4 = i__; x[i__4].r = 0., x[i__4].i = 0.; /* L100: */ } i__3 = j; x[i__3].r = 1., x[i__3].i = 0.; xj = 1.; *scale = 0.; xmax = 0.; } L110: /* Scale x if necessary to avoid overflow when adding a */ /* multiple of column j of A. */ if (xj > 1.) { rec = 1. / xj; if (cnorm[j] > (bignum - xmax) * rec) { /* Scale x by 1/(2*abs(x(j))). */ rec *= .5; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; } } else if (xj * cnorm[j] > bignum - xmax) { /* Scale x by 1/2. */ zdscal_(n, &c_b36, &x[1], &c__1); *scale *= .5; } if (upper) { if (j > 1) { /* Compute the update */ /* x(max(1,j-kd):j-1) := x(max(1,j-kd):j-1) - */ /* x(j)* A(max(1,j-kd):j-1,j) */ /* Computing MIN */ i__3 = *kd, i__4 = j - 1; jlen = min(i__3,i__4); i__3 = j; z__2.r = -x[i__3].r, z__2.i = -x[i__3].i; z__1.r = tscal * z__2.r, z__1.i = tscal * z__2.i; zaxpy_(&jlen, &z__1, &ab[*kd + 1 - jlen + j * ab_dim1] , &c__1, &x[j - jlen], &c__1); i__3 = j - 1; i__ = izamax_(&i__3, &x[1], &c__1); i__3 = i__; xmax = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag( &x[i__]), abs(d__2)); } } else if (j < *n) { /* Compute the update */ /* x(j+1:min(j+kd,n)) := x(j+1:min(j+kd,n)) - */ /* x(j) * A(j+1:min(j+kd,n),j) */ /* Computing MIN */ i__3 = *kd, i__4 = *n - j; jlen = min(i__3,i__4); if (jlen > 0) { i__3 = j; z__2.r = -x[i__3].r, z__2.i = -x[i__3].i; z__1.r = tscal * z__2.r, z__1.i = tscal * z__2.i; zaxpy_(&jlen, &z__1, &ab[j * ab_dim1 + 2], &c__1, &x[ j + 1], &c__1); } i__3 = *n - j; i__ = j + izamax_(&i__3, &x[j + 1], &c__1); i__3 = i__; xmax = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[ i__]), abs(d__2)); } /* L120: */ } } else if (lsame_(trans, "T")) { /* Solve A**T * x = b */ i__2 = jlast; i__1 = jinc; for (j = jfirst; i__1 < 0 ? j >= i__2 : j <= i__2; j += i__1) { /* Compute x(j) = b(j) - sum A(k,j)*x(k). */ /* k<>j */ i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]), abs(d__2)); uscal.r = tscal, uscal.i = 0.; rec = 1. / max(xmax,1.); if (cnorm[j] > (bignum - xj) * rec) { /* If x(j) could overflow, scale x by 1/(2*XMAX). */ rec *= .5; if (nounit) { i__3 = maind + j * ab_dim1; z__1.r = tscal * ab[i__3].r, z__1.i = tscal * ab[i__3] .i; tjjs.r = z__1.r, tjjs.i = z__1.i; } else { tjjs.r = tscal, tjjs.i = 0.; } tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs(d__2)); if (tjj > 1.) { /* Divide by A(j,j) when scaling x if A(j,j) > 1. */ /* Computing MIN */ d__1 = 1., d__2 = rec * tjj; rec = min(d__1,d__2); zladiv_(&z__1, &uscal, &tjjs); uscal.r = z__1.r, uscal.i = z__1.i; } if (rec < 1.) { zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } } csumj.r = 0., csumj.i = 0.; if (uscal.r == 1. && uscal.i == 0.) { /* If the scaling needed for A in the dot product is 1, */ /* call ZDOTU to perform the dot product. */ if (upper) { /* Computing MIN */ i__3 = *kd, i__4 = j - 1; jlen = min(i__3,i__4); zdotu_(&z__1, &jlen, &ab[*kd + 1 - jlen + j * ab_dim1] , &c__1, &x[j - jlen], &c__1); csumj.r = z__1.r, csumj.i = z__1.i; } else { /* Computing MIN */ i__3 = *kd, i__4 = *n - j; jlen = min(i__3,i__4); if (jlen > 1) { zdotu_(&z__1, &jlen, &ab[j * ab_dim1 + 2], &c__1, &x[j + 1], &c__1); csumj.r = z__1.r, csumj.i = z__1.i; } } } else { /* Otherwise, use in-line code for the dot product. */ if (upper) { /* Computing MIN */ i__3 = *kd, i__4 = j - 1; jlen = min(i__3,i__4); i__3 = jlen; for (i__ = 1; i__ <= i__3; ++i__) { i__4 = *kd + i__ - jlen + j * ab_dim1; z__3.r = ab[i__4].r * uscal.r - ab[i__4].i * uscal.i, z__3.i = ab[i__4].r * uscal.i + ab[i__4].i * uscal.r; i__5 = j - jlen - 1 + i__; z__2.r = z__3.r * x[i__5].r - z__3.i * x[i__5].i, z__2.i = z__3.r * x[i__5].i + z__3.i * x[ i__5].r; z__1.r = csumj.r + z__2.r, z__1.i = csumj.i + z__2.i; csumj.r = z__1.r, csumj.i = z__1.i; /* L130: */ } } else { /* Computing MIN */ i__3 = *kd, i__4 = *n - j; jlen = min(i__3,i__4); i__3 = jlen; for (i__ = 1; i__ <= i__3; ++i__) { i__4 = i__ + 1 + j * ab_dim1; z__3.r = ab[i__4].r * uscal.r - ab[i__4].i * uscal.i, z__3.i = ab[i__4].r * uscal.i + ab[i__4].i * uscal.r; i__5 = j + i__; z__2.r = z__3.r * x[i__5].r - z__3.i * x[i__5].i, z__2.i = z__3.r * x[i__5].i + z__3.i * x[ i__5].r; z__1.r = csumj.r + z__2.r, z__1.i = csumj.i + z__2.i; csumj.r = z__1.r, csumj.i = z__1.i; /* L140: */ } } } z__1.r = tscal, z__1.i = 0.; if (uscal.r == z__1.r && uscal.i == z__1.i) { /* Compute x(j) := ( x(j) - CSUMJ ) / A(j,j) if 1/A(j,j) */ /* was not used to scale the dotproduct. */ i__3 = j; i__4 = j; z__1.r = x[i__4].r - csumj.r, z__1.i = x[i__4].i - csumj.i; x[i__3].r = z__1.r, x[i__3].i = z__1.i; i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]) , abs(d__2)); if (nounit) { /* Compute x(j) = x(j) / A(j,j), scaling if necessary. */ i__3 = maind + j * ab_dim1; z__1.r = tscal * ab[i__3].r, z__1.i = tscal * ab[i__3] .i; tjjs.r = z__1.r, tjjs.i = z__1.i; } else { tjjs.r = tscal, tjjs.i = 0.; if (tscal == 1.) { goto L160; } } tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs(d__2)); if (tjj > smlnum) { /* abs(A(j,j)) > SMLNUM: */ if (tjj < 1.) { if (xj > tjj * bignum) { /* Scale X by 1/abs(x(j)). */ rec = 1. / xj; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; } else if (tjj > 0.) { /* 0 < abs(A(j,j)) <= SMLNUM: */ if (xj > tjj * bignum) { /* Scale x by (1/abs(x(j)))*abs(A(j,j))*BIGNUM. */ rec = tjj * bignum / xj; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; } else { /* A(j,j) = 0: Set x(1:n) = 0, x(j) = 1, and */ /* scale = 0 and compute a solution to A**T *x = 0. */ i__3 = *n; for (i__ = 1; i__ <= i__3; ++i__) { i__4 = i__; x[i__4].r = 0., x[i__4].i = 0.; /* L150: */ } i__3 = j; x[i__3].r = 1., x[i__3].i = 0.; *scale = 0.; xmax = 0.; } L160: ; } else { /* Compute x(j) := x(j) / A(j,j) - CSUMJ if the dot */ /* product has already been divided by 1/A(j,j). */ i__3 = j; zladiv_(&z__2, &x[j], &tjjs); z__1.r = z__2.r - csumj.r, z__1.i = z__2.i - csumj.i; x[i__3].r = z__1.r, x[i__3].i = z__1.i; } /* Computing MAX */ i__3 = j; d__3 = xmax, d__4 = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]), abs(d__2)); xmax = max(d__3,d__4); /* L170: */ } } else { /* Solve A**H * x = b */ i__1 = jlast; i__2 = jinc; for (j = jfirst; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) { /* Compute x(j) = b(j) - sum A(k,j)*x(k). */ /* k<>j */ i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]), abs(d__2)); uscal.r = tscal, uscal.i = 0.; rec = 1. / max(xmax,1.); if (cnorm[j] > (bignum - xj) * rec) { /* If x(j) could overflow, scale x by 1/(2*XMAX). */ rec *= .5; if (nounit) { d_cnjg(&z__2, &ab[maind + j * ab_dim1]); z__1.r = tscal * z__2.r, z__1.i = tscal * z__2.i; tjjs.r = z__1.r, tjjs.i = z__1.i; } else { tjjs.r = tscal, tjjs.i = 0.; } tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs(d__2)); if (tjj > 1.) { /* Divide by A(j,j) when scaling x if A(j,j) > 1. */ /* Computing MIN */ d__1 = 1., d__2 = rec * tjj; rec = min(d__1,d__2); zladiv_(&z__1, &uscal, &tjjs); uscal.r = z__1.r, uscal.i = z__1.i; } if (rec < 1.) { zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } } csumj.r = 0., csumj.i = 0.; if (uscal.r == 1. && uscal.i == 0.) { /* If the scaling needed for A in the dot product is 1, */ /* call ZDOTC to perform the dot product. */ if (upper) { /* Computing MIN */ i__3 = *kd, i__4 = j - 1; jlen = min(i__3,i__4); zdotc_(&z__1, &jlen, &ab[*kd + 1 - jlen + j * ab_dim1] , &c__1, &x[j - jlen], &c__1); csumj.r = z__1.r, csumj.i = z__1.i; } else { /* Computing MIN */ i__3 = *kd, i__4 = *n - j; jlen = min(i__3,i__4); if (jlen > 1) { zdotc_(&z__1, &jlen, &ab[j * ab_dim1 + 2], &c__1, &x[j + 1], &c__1); csumj.r = z__1.r, csumj.i = z__1.i; } } } else { /* Otherwise, use in-line code for the dot product. */ if (upper) { /* Computing MIN */ i__3 = *kd, i__4 = j - 1; jlen = min(i__3,i__4); i__3 = jlen; for (i__ = 1; i__ <= i__3; ++i__) { d_cnjg(&z__4, &ab[*kd + i__ - jlen + j * ab_dim1]) ; z__3.r = z__4.r * uscal.r - z__4.i * uscal.i, z__3.i = z__4.r * uscal.i + z__4.i * uscal.r; i__4 = j - jlen - 1 + i__; z__2.r = z__3.r * x[i__4].r - z__3.i * x[i__4].i, z__2.i = z__3.r * x[i__4].i + z__3.i * x[ i__4].r; z__1.r = csumj.r + z__2.r, z__1.i = csumj.i + z__2.i; csumj.r = z__1.r, csumj.i = z__1.i; /* L180: */ } } else { /* Computing MIN */ i__3 = *kd, i__4 = *n - j; jlen = min(i__3,i__4); i__3 = jlen; for (i__ = 1; i__ <= i__3; ++i__) { d_cnjg(&z__4, &ab[i__ + 1 + j * ab_dim1]); z__3.r = z__4.r * uscal.r - z__4.i * uscal.i, z__3.i = z__4.r * uscal.i + z__4.i * uscal.r; i__4 = j + i__; z__2.r = z__3.r * x[i__4].r - z__3.i * x[i__4].i, z__2.i = z__3.r * x[i__4].i + z__3.i * x[ i__4].r; z__1.r = csumj.r + z__2.r, z__1.i = csumj.i + z__2.i; csumj.r = z__1.r, csumj.i = z__1.i; /* L190: */ } } } z__1.r = tscal, z__1.i = 0.; if (uscal.r == z__1.r && uscal.i == z__1.i) { /* Compute x(j) := ( x(j) - CSUMJ ) / A(j,j) if 1/A(j,j) */ /* was not used to scale the dotproduct. */ i__3 = j; i__4 = j; z__1.r = x[i__4].r - csumj.r, z__1.i = x[i__4].i - csumj.i; x[i__3].r = z__1.r, x[i__3].i = z__1.i; i__3 = j; xj = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]) , abs(d__2)); if (nounit) { /* Compute x(j) = x(j) / A(j,j), scaling if necessary. */ d_cnjg(&z__2, &ab[maind + j * ab_dim1]); z__1.r = tscal * z__2.r, z__1.i = tscal * z__2.i; tjjs.r = z__1.r, tjjs.i = z__1.i; } else { tjjs.r = tscal, tjjs.i = 0.; if (tscal == 1.) { goto L210; } } tjj = (d__1 = tjjs.r, abs(d__1)) + (d__2 = d_imag(&tjjs), abs(d__2)); if (tjj > smlnum) { /* abs(A(j,j)) > SMLNUM: */ if (tjj < 1.) { if (xj > tjj * bignum) { /* Scale X by 1/abs(x(j)). */ rec = 1. / xj; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; } else if (tjj > 0.) { /* 0 < abs(A(j,j)) <= SMLNUM: */ if (xj > tjj * bignum) { /* Scale x by (1/abs(x(j)))*abs(A(j,j))*BIGNUM. */ rec = tjj * bignum / xj; zdscal_(n, &rec, &x[1], &c__1); *scale *= rec; xmax *= rec; } i__3 = j; zladiv_(&z__1, &x[j], &tjjs); x[i__3].r = z__1.r, x[i__3].i = z__1.i; } else { /* A(j,j) = 0: Set x(1:n) = 0, x(j) = 1, and */ /* scale = 0 and compute a solution to A**H *x = 0. */ i__3 = *n; for (i__ = 1; i__ <= i__3; ++i__) { i__4 = i__; x[i__4].r = 0., x[i__4].i = 0.; /* L200: */ } i__3 = j; x[i__3].r = 1., x[i__3].i = 0.; *scale = 0.; xmax = 0.; } L210: ; } else { /* Compute x(j) := x(j) / A(j,j) - CSUMJ if the dot */ /* product has already been divided by 1/A(j,j). */ i__3 = j; zladiv_(&z__2, &x[j], &tjjs); z__1.r = z__2.r - csumj.r, z__1.i = z__2.i - csumj.i; x[i__3].r = z__1.r, x[i__3].i = z__1.i; } /* Computing MAX */ i__3 = j; d__3 = xmax, d__4 = (d__1 = x[i__3].r, abs(d__1)) + (d__2 = d_imag(&x[j]), abs(d__2)); xmax = max(d__3,d__4); /* L220: */ } } *scale /= tscal; } /* Scale the column norms by 1/TSCAL for return. */ if (tscal != 1.) { d__1 = 1. / tscal; dscal_(n, &d__1, &cnorm[1], &c__1); } return 0; /* End of ZLATBS */ } /* zlatbs_ */