/*! \file
Copyright (c) 2003, The Regents of the University of California, through
Lawrence Berkeley National Laboratory (subject to receipt of any required
approvals from U.S. Dept. of Energy)

All rights reserved.

The source code is distributed under BSD license, see the file License.txt
at the top-level directory.
*/

/*
 * -- SuperLU routine (version 3.0) --
 * Lawrence Berkeley National Lab, Univ. of California Berkeley,
 * and Xerox Palo Alto Research Center.
 * September 10, 2007
 *
 */
#include <math.h>
#include "slu_mt_Cnames.h"
#include "slu_mt_cdefs.h"
#include "slu_mt_util.h"
#include "slu_scomplex.h"

int_t clacon_(int_t* n, complex* v, complex* x, float* est, int_t* kase)

{
    /*
        Purpose
        =======

        CLACON estimates the 1-norm of a square matrix A.
        Reverse communication is used for evaluating matrix-vector products.


        Arguments
        =========

        N      (input) INT_T
               The order of the matrix.  N >= 1.

        V      (workspace) COMPLEX PRECISION array, dimension (N)
               On the final return, V = A*W,  where  EST = norm(V)/norm(W)
               (W is not returned).

        X      (input/output) COMPLEX PRECISION 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 CLACON must be re-called with all the other parameters
               unchanged.


        EST    (output) FLOAT PRECISION
               An estimate (a lower bound) for norm(A).

        KASE   (input/output) INT_T
               On the initial call to CLACON, 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 CLACON, 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.
        =====================================================================
    */

    /* Table of constant values */
    int c__1 = 1;
    int ni = *n;
    complex zero = {0.0, 0.0};
    complex one = {1.0, 0.0};

    /* System generated locals */
    float d__1;

    /* Local variables */
    static int_t iter;
    static int_t jump, jlast;
    static float altsgn, estold;
    static int_t i, j;
    float temp;
    float safmin;
    extern double slamch_(char*);
    extern int icmax1_(int*, complex*, int*);
    extern double scsum1_(int*, complex*, int*);
    extern int ccopy_(int*, complex*, int*, complex*, int*);

    safmin = slamch_("Safe minimum");
    if(*kase == 0) {
        for(i = 0; i < *n; ++i) {
            x[i].r = 1. / (float)(*n);
            x[i].i = 0.;
        }
        *kase = 1;
        jump = 1;
        return 0;
    }

    switch(jump) {
    case 1:
        goto L20;
    case 2:
        goto L40;
    case 3:
        goto L70;
    case 4:
        goto L110;
    case 5:
        goto L140;
    }

    /*     ................ ENTRY   (JUMP = 1)
       FIRST ITERATION.  X HAS BEEN OVERWRITTEN BY A*X. */
L20:
    if(*n == 1) {
        v[0] = x[0];
        *est = c_abs(&v[0]);
        /*        ... QUIT */
        goto L150;
    }
    *est = scsum1_(&ni, x, &c__1);

    for(i = 0; i < *n; ++i) {
        d__1 = c_abs(&x[i]);
        if(d__1 > safmin) {
            d__1 = 1 / d__1;
            x[i].r *= d__1;
            x[i].i *= d__1;
        }
        else {
            x[i] = one;
        }
    }
    *kase = 2;
    jump = 2;
    return 0;

    /*     ................ ENTRY   (JUMP = 2)
       FIRST ITERATION.  X HAS BEEN OVERWRITTEN BY TRANSPOSE(A)*X. */
L40:
    j = icmax1_(&ni, &x[0], &c__1);
    --j;
    iter = 2;

    /*     MAIN LOOP - ITERATIONS 2,3,...,ITMAX. */
L50:
    for(i = 0; i < *n; ++i) x[i] = zero;
    x[j] = one;
    *kase = 1;
    jump = 3;
    return 0;

    /*     ................ ENTRY   (JUMP = 3)
       X HAS BEEN OVERWRITTEN BY A*X. */
L70:
    ccopy_(&ni, &x[0], &c__1, &v[0], &c__1);
    estold = *est;
    *est = scsum1_(&ni, v, &c__1);

L90:
    /*     TEST FOR CYCLING. */
    if(*est <= estold) goto L120;

    for(i = 0; i < *n; ++i) {
        d__1 = c_abs(&x[i]);
        if(d__1 > safmin) {
            d__1 = 1 / d__1;
            x[i].r *= d__1;
            x[i].i *= d__1;
        }
        else {
            x[i] = one;
        }
    }
    *kase = 2;
    jump = 4;
    return 0;

    /*     ................ ENTRY   (JUMP = 4)
       X HAS BEEN OVERWRITTEN BY TRANDPOSE(A)*X. */
L110:
    jlast = j;
    j = icmax1_(&ni, &x[0], &c__1);
    --j;
    if(x[jlast].r != (d__1 = x[j].r, fabs(d__1)) && iter < 5) {
        ++iter;
        goto L50;
    }

    /*     ITERATION COMPLETE.  FINAL STAGE. */
L120:
    altsgn = 1.;
    for(i = 1; i <= *n; ++i) {
        x[i - 1].r = altsgn * ((float)(i - 1) / (float)(*n - 1) + 1.);
        x[i - 1].i = 0.;
        altsgn = -altsgn;
    }
    *kase = 1;
    jump = 5;
    return 0;

    /*     ................ ENTRY   (JUMP = 5)
       X HAS BEEN OVERWRITTEN BY A*X. */
L140:
    temp = scsum1_(&ni, x, &c__1) / (float)(*n * 3) * 2.;
    if(temp > *est) {
        ccopy_(&ni, &x[0], &c__1, &v[0], &c__1);
        *est = temp;
    }

L150:
    *kase = 0;
    return 0;

} /* clacon_ */
