#include "f2c.h" #include "blaswrap.h" /* Table of constant values */ static integer c__1 = 1; /* Subroutine */ int zlacon_(integer *n, doublecomplex *v, doublecomplex *x, doublereal *est, integer *kase) { /* System generated locals */ integer i__1, i__2, i__3; doublereal d__1, d__2; doublecomplex z__1; /* Builtin functions */ double z_abs(doublecomplex *), d_imag(doublecomplex *); /* Local variables */ static integer i__, j, iter; static doublereal temp; static integer jump; static doublereal absxi; static integer jlast; extern /* Subroutine */ int zcopy_(integer *, doublecomplex *, integer *, doublecomplex *, integer *); extern integer izmax1_(integer *, doublecomplex *, integer *); extern doublereal dzsum1_(integer *, doublecomplex *, integer *), dlamch_( char *); static doublereal safmin, altsgn, estold; /* -- LAPACK auxiliary routine (version 3.1) -- */ /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ /* November 2006 */ /* .. Scalar Arguments .. */ /* .. */ /* .. Array Arguments .. */ /* .. */ /* Purpose */ /* ======= */ /* ZLACON estimates the 1-norm of a square, complex matrix A. */ /* Reverse communication is used for evaluating matrix-vector products. */ /* Arguments */ /* ========= */ /* N (input) INTEGER */ /* The order of the matrix. N >= 1. */ /* V (workspace) COMPLEX*16 array, dimension (N) */ /* On the final return, V = A*W, where EST = norm(V)/norm(W) */ /* (W is not returned). */ /* X (input/output) COMPLEX*16 array, dimension (N) */ /* On an intermediate return, X should be overwritten by */ /* A * X, if KASE=1, */ /* A' * X, if KASE=2, */ /* where A' is the conjugate transpose of A, and ZLACON must be */ /* re-called with all the other parameters unchanged. */ /* EST (input/output) DOUBLE PRECISION */ /* On entry with KASE = 1 or 2 and JUMP = 3, EST should be */ /* unchanged from the previous call to ZLACON. */ /* On exit, EST is an estimate (a lower bound) for norm(A). */ /* KASE (input/output) INTEGER */ /* On the initial call to ZLACON, KASE should be 0. */ /* On an intermediate return, KASE will be 1 or 2, indicating */ /* whether X should be overwritten by A * X or A' * X. */ /* On the final return from ZLACON, KASE will again be 0. */ /* Further Details */ /* ======= ======= */ /* Contributed by Nick Higham, University of Manchester. */ /* Originally named CONEST, dated March 16, 1988. */ /* Reference: N.J. Higham, "FORTRAN codes for estimating the one-norm of */ /* a real or complex matrix, with applications to condition estimation", */ /* ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988. */ /* Last modified: April, 1999 */ /* ===================================================================== */ /* .. Parameters .. */ /* .. */ /* .. Local Scalars .. */ /* .. */ /* .. External Functions .. */ /* .. */ /* .. External Subroutines .. */ /* .. */ /* .. Intrinsic Functions .. */ /* .. */ /* .. Save statement .. */ /* .. */ /* .. Executable Statements .. */ /* Parameter adjustments */ --x; --v; /* Function Body */ safmin = dlamch_("Safe minimum"); if (*kase == 0) { i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { i__2 = i__; d__1 = 1. / (doublereal) (*n); z__1.r = d__1, z__1.i = 0.; x[i__2].r = z__1.r, x[i__2].i = z__1.i; /* L10: */ } *kase = 1; jump = 1; return 0; } switch (jump) { case 1: goto L20; case 2: goto L40; case 3: goto L70; case 4: goto L90; case 5: goto L120; } /* ................ ENTRY (JUMP = 1) */ /* FIRST ITERATION. X HAS BEEN OVERWRITTEN BY A*X. */ L20: if (*n == 1) { v[1].r = x[1].r, v[1].i = x[1].i; *est = z_abs(&v[1]); /* ... QUIT */ goto L130; } *est = dzsum1_(n, &x[1], &c__1); i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { absxi = z_abs(&x[i__]); if (absxi > safmin) { i__2 = i__; i__3 = i__; d__1 = x[i__3].r / absxi; d__2 = d_imag(&x[i__]) / absxi; z__1.r = d__1, z__1.i = d__2; x[i__2].r = z__1.r, x[i__2].i = z__1.i; } else { i__2 = i__; x[i__2].r = 1., x[i__2].i = 0.; } /* L30: */ } *kase = 2; jump = 2; return 0; /* ................ ENTRY (JUMP = 2) */ /* FIRST ITERATION. X HAS BEEN OVERWRITTEN BY CTRANS(A)*X. */ L40: j = izmax1_(n, &x[1], &c__1); iter = 2; /* MAIN LOOP - ITERATIONS 2,3,...,ITMAX. */ L50: i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { i__2 = i__; x[i__2].r = 0., x[i__2].i = 0.; /* L60: */ } i__1 = j; x[i__1].r = 1., x[i__1].i = 0.; *kase = 1; jump = 3; return 0; /* ................ ENTRY (JUMP = 3) */ /* X HAS BEEN OVERWRITTEN BY A*X. */ L70: zcopy_(n, &x[1], &c__1, &v[1], &c__1); estold = *est; *est = dzsum1_(n, &v[1], &c__1); /* TEST FOR CYCLING. */ if (*est <= estold) { goto L100; } i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { absxi = z_abs(&x[i__]); if (absxi > safmin) { i__2 = i__; i__3 = i__; d__1 = x[i__3].r / absxi; d__2 = d_imag(&x[i__]) / absxi; z__1.r = d__1, z__1.i = d__2; x[i__2].r = z__1.r, x[i__2].i = z__1.i; } else { i__2 = i__; x[i__2].r = 1., x[i__2].i = 0.; } /* L80: */ } *kase = 2; jump = 4; return 0; /* ................ ENTRY (JUMP = 4) */ /* X HAS BEEN OVERWRITTEN BY CTRANS(A)*X. */ L90: jlast = j; j = izmax1_(n, &x[1], &c__1); if (z_abs(&x[jlast]) != z_abs(&x[j]) && iter < 5) { ++iter; goto L50; } /* ITERATION COMPLETE. FINAL STAGE. */ L100: altsgn = 1.; i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { i__2 = i__; d__1 = altsgn * ((doublereal) (i__ - 1) / (doublereal) (*n - 1) + 1.); z__1.r = d__1, z__1.i = 0.; x[i__2].r = z__1.r, x[i__2].i = z__1.i; altsgn = -altsgn; /* L110: */ } *kase = 1; jump = 5; return 0; /* ................ ENTRY (JUMP = 5) */ /* X HAS BEEN OVERWRITTEN BY A*X. */ L120: temp = dzsum1_(n, &x[1], &c__1) / (doublereal) (*n * 3) * 2.; if (temp > *est) { zcopy_(n, &x[1], &c__1, &v[1], &c__1); *est = temp; } L130: *kase = 0; return 0; /* End of ZLACON */ } /* zlacon_ */