snlaso.c

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#include "f2c.h"
#include "netlib.h"
extern double sqrt(double); /* #include <math.h> */

static void slabax_(const integer *n, const integer *nband, real *a, real *x, real *y);
static void slabcm_(const integer *n, const integer *nband, const integer *nl, const integer *nr,
                    real *a, real *eigval, const integer *lde, real *eigvec,
                    real *atol, real *artol, real *bound, real *atemp, real *d, real *vtemp);
static void slabfc_(const integer *n, const integer *nband, real *a, real *sigma, const integer *number,
                    const integer *lde, real *eigvec, integer *numl, integer *ldad,
                    real *atemp, real *d, real *atol);
static void slaeig_(const integer *n, const integer *nband, const integer *nl, const integer *nr,
                    real *a, real *eigval, const integer *lde,
                    real *eigvec, real *bound, real *atemp, real *d,
                    real *vtemp, real *eps, real *tmin, real *tmax);
static void slager_(const integer *n, const integer *nband, const integer *nstart,
                    real *a, real *tmin, real *tmax);
static void slaran_(const integer *n, real *x);
static void smvpc_(const integer *nblock, const real *bet, const integer *maxj, const integer *j,
                   const real *s, const integer *number, real *resnrm, real *orthcf, real *rv);
static void snppla_(void (*op)(const integer*,const integer*,const real*,real*),
                    void (*iovect)(const integer*,const integer*,real*,const integer*,const integer*),
                    const integer *n, const integer *nperm, integer *nop, const integer *nmval,
                    real *val, const integer *nmvec, real *vec, const integer *nblock,
                    real *h, real *hv, real *p, real *q, real *bound,
                    real *d, real *delta, logical *small, logical *raritz, real *eps);
static void snwla_(void (*op)(const integer*,const integer*,const real*,real*),
                   void (*iovect)(const integer*,const integer*,real*,const integer*,const integer*),
                   const integer *n, const integer *nband, const integer *nval,
                   const integer *nfig, integer *nperm, real *val, const integer *nmvec, real *vec,
                   const integer *nblock, const integer *maxop, const integer *maxj, integer *nop,
                   real *p1, real *p0, real *res, real *tau, real *otau,
                   real *t, real *alp, real *bet, real *s, real *p2,
                   real *bound, real *atemp, real *vtemp,
                   real *d, integer *ind, logical *small, logical *raritz,
                   real *delta, real *eps, integer *ierr);
static void sortqr_(const integer *nz, const integer *n, const integer *nblock, real *z, real *b);
static void svsort_(const integer *num, real *val, real *res, const integer *iflag,
                    real *v, const integer *nmvec, const integer *n, real *vec);

/* Table of constant values */
static integer c__0 = 0;
static integer c__1 = 1;
static real c__10 = 0.1f;
static real c__00 = 0.0f;

/*   VERSION 2    DOES NOT USE EISPACK */

/* ------------------------------------------------------------------ */

/* Subroutine */ void snlaso_(op, iovect, n, nval, nfig, nperm, nmval, val, nmvec, vec, nblock, maxop, maxj, work, ind, ierr)
void (*op) (const integer* n,const integer* m,const real* p,real* q);
void (*iovect) (const integer* n,const integer* m,real* q,const integer* j,const integer* k);
const integer *n, *nval, *nfig, *nmval;
integer *nperm;
real *val;
const integer *nmvec;
real *vec;
const integer *nblock, *maxop, *maxj;
real *work;
integer *ind, *ierr;
{
    /* Local variables */
    static real temp, tarr;
    static integer i, m, nband;
    static real delta;
    static logical small;
    static integer i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, nv;
    static logical raritz;
    static real eps;
    static integer nop;

/* AUTHOR/IMPLEMENTER D.S.SCOTT-B.N.PARLETT/D.S.SCOTT */
/*                                                    */
/* COMPUTER SCIENCES DEPARTMENT                       */
/* UNIVERSITY OF TEXAS AT AUSTIN                      */
/* AUSTIN, TX 78712                                   */
/*                                                    */
/* VERSION 2 ORIGINATED APRIL 1982                    */
/*                                                    */
/* CURRENT VERSION  JUNE 1983                         */

/* SNLASO FINDS A FEW EIGENVALUES AND EIGENVECTORS AT EITHER END OF     */
/* THE SPECTRUM OF A LARGE SPARSE SYMMETRIC MATRIX.  THE SUBROUTINE     */
/* SNLASO IS PRIMARILY A DRIVER FOR SUBROUTINE SNWLA WHICH IMPLEMENTS   */
/* THE LANCZOS ALGORITHM WITH SELECTIVE ORTHOGONALIZATION AND           */
/* SUBROUTINE SNPPLA WHICH POST PROCESSES THE OUTPUT OF SNWLA.          */
/* HOWEVER SNLASO DOES CHECK FOR INCONSISTENCIES IN THE CALLING         */
/* PARAMETERS AND DOES PREPROCESS ANY USER SUPPLIED EIGENPAIRS.         */
/* SNLASO ALWAYS LOOKS FOR THE SMALLEST (LEFTMOST) EIGENVALUES.  IF     */
/* THE LARGEST EIGENVALUES ARE DESIRED SNLASO IMPLICITLY USES THE       */
/* NEGATIVE OF THE MATRIX.                                              */
/*                                                                      */
/* ON INPUT                                                             */
/*                                                                      */
/*   OP   A USER SUPPLIED SUBROUTINE WITH CALLING SEQUENCE              */
/*     OP(N,M,P,Q).  P AND Q ARE N X M MATRICES AND Q IS                */
/*     RETURNED AS THE MATRIX TIMES P.                                  */
/*                                                                      */
/*   IOVECT   A USER SUPPLIED SUBROUTINE WITH CALLING SEQUENCE          */
/*     IOVECT(N,M,Q,J,K).  Q IS AN N X M MATRIX.  IF K = 0              */
/*     THE COLUMNS OF Q ARE STORED AS THE (J-M+1)TH THROUGH             */
/*     THE JTH LANCZOS VECTORS.  IF K = 1 THEN Q IS RETURNED            */
/*     AS THE (J-M+1)TH THROUGH THE JTH LANCZOS VECTORS.  SEE           */
/*     DOCUMENTATION FOR FURTHER DETAILS AND EXAMPLES.                  */
/*                                                                      */
/*   N   THE ORDER OF THE MATRIX.                                       */
/*                                                                      */
/*   NVAL   NVAL SPECIFIES THE EIGENVALUES TO BE FOUND.                 */
/*     ABS(NVAL)  IS THE NUMBER OF EIGENVALUES DESIRED.                 */
/*     IF NVAL < 0 THE ALGEBRAICALLY SMALLEST (LEFTMOST)                */
/*     EIGENVALUES ARE FOUND.  IF NVAL > 0 THE ALGEBRAICALLY            */
/*     LARGEST (RIGHTMOST) EIGENVALUES ARE FOUND.  NVAL MUST NOT        */
/*     BE ZERO.  ABS(NVAL) MUST BE LESS THAN  MAXJ/2.                   */
/*                                                                      */
/*   NFIG   THE NUMBER OF DECIMAL DIGITS OF ACCURACY DESIRED IN THE     */
/*     EIGENVALUES.  NFIG MUST BE GREATER THAN OR EQUAL TO 1.           */
/*                                                                      */
/*   NPERM   AN INTEGER VARIABLE WHICH SPECIFIES THE NUMBER OF USER     */
/*     SUPPLIED EIGENPAIRS.  IN MOST CASES NPERM WILL BE ZERO.  SEE     */
/*     DOCUMENTAION FOR FURTHER DETAILS OF USING NPERM GREATER          */
/*     THAN ZERO.  NPERM MUST NOT BE LESS THAN ZERO.                    */
/*                                                                      */
/*   NMVAL   THE ROW DIMENSION OF THE ARRAY VAL.  NMVAL MUST BE GREATER */
/*     THAN OR EQUAL TO ABS(NVAL).                                      */
/*                                                                      */
/*   VAL   A TWO DIMENSIONAL REAL ARRAY OF ROW                          */
/*     DIMENSION NMVAL AND COLUMN DIMENSION AT LEAST 4.  IF NPERM       */
/*     IS GREATER THAN ZERO THEN CERTAIN INFORMATION MUST BE STORED     */
/*     IN VAL.  SEE DOCUMENTATION FOR DETAILS.                          */
/*                                                                      */
/*   NMVEC   THE ROW DIMENSION OF THE ARRAY VEC.  NMVEC MUST BE GREATER */
/*     THAN OR EQUAL TO N.                                              */
/*                                                                      */
/*   VEC   A TWO DIMENSIONAL REAL ARRAY OF ROW                          */
/*     DIMENSION NMVEC AND COLUMN DIMENSION AT LEAST ABS(NVAL).  IF     */
/*     NPERM > 0 THEN THE FIRST NPERM COLUMNS OF VEC MUST               */
/*     CONTAIN THE USER SUPPLIED EIGENVECTORS.                          */
/*                                                                      */
/*   NBLOCK   THE BLOCK SIZE.  SEE DOCUMENTATION FOR CHOOSING           */
/*     AN APPROPRIATE VALUE FOR NBLOCK.  NBLOCK MUST BE GREATER         */
/*     THAN ZERO AND LESS THAN  MAXJ/6.                                 */
/*                                                                      */
/*   MAXOP   AN UPPER BOUND ON THE NUMBER OF CALLS TO THE SUBROUTINE    */
/*     OP.  SNLASO TERMINATES WHEN MAXOP IS EXCEEDED.  SEE              */
/*     DOCUMENTATION FOR GUIDELINES IN CHOOSING A VALUE FOR MAXOP.      */
/*                                                                      */
/*   MAXJ   AN INDICATION OF THE AVAILABLE STORAGE (SEE WORK AND        */
/*     DOCUMENTATION ON IOVECT).  FOR THE FASTEST CONVERGENCE MAXJ      */
/*     SHOULD BE AS LARGE AS POSSIBLE, ALTHOUGH IT IS USELESS TO HAVE   */
/*     MAXJ LARGER THAN MAXOP*NBLOCK.                                   */
/*                                                                      */
/*   WORK   A REAL ARRAY OF DIMENSION AT LEAST AS                       */
/*     LARGE AS                                                         */
/*                                                                      */
/*         2*N*NBLOCK + MAXJ*(NBLOCK+NV+2) + 2*NBLOCK*NBLOCK + 3*NV     */
/*                                                                      */
/*            + THE MAXIMUM OF                                          */
/*                 N*NBLOCK                                             */
/*                   AND                                                */
/*         MAXJ*(2*NBLOCK+3) + 2*NV + 6 + (2*NBLOCK+2)*(NBLOCK+1)       */
/*                                                                      */
/*     WHERE NV = ABS(NVAL)                                             */
/*                                                                      */
/*     THE FIRST N*NBLOCK ELEMENTS OF WORK MUST CONTAIN THE DESIRED     */
/*     STARTING VECTORS.  SEE DOCUMENTATION FOR GUIDELINES IN           */
/*     CHOOSING STARTING VECTORS.                                       */
/*                                                                      */
/*   IND   AN INTEGER ARRAY OF DIMENSION AT LEAST ABS(NVAL).            */
/*                                                                      */
/*   IERR   AN INTEGER VARIABLE.                                        */
/*                                                                      */
/* ON OUTPUT                                                            */
/*                                                                      */
/*   NPERM   THE NUMBER OF EIGENPAIRS NOW KNOWN.                        */
/*                                                                      */
/*   VEC   THE FIRST NPERM COLUMNS OF VEC CONTAIN THE EIGENVECTORS.     */
/*                                                                      */
/*   VAL   THE FIRST COLUMN OF VAL CONTAINS THE CORRESPONDING           */
/*     EIGENVALUES.  THE SECOND COLUMN CONTAINS THE RESIDUAL NORMS OF   */
/*     THE EIGENPAIRS WHICH ARE BOUNDS ON THE ACCURACY OF THE EIGEN-    */
/*     VALUES.  THE THIRD COLUMN CONTAINS MORE REALISTIC ESTIMATES      */
/*     OF THE ACCURACY OF THE EIGENVALUES.  THE FOURTH COLUMN CONTAINS  */
/*     ESTIMATES OF THE ACCURACY OF THE EIGENVECTORS.  SEE              */
/*     DOCUMENTATION FOR FURTHER INFORMATION ON THESE QUANTITIES.       */
/*                                                                      */
/*   WORK   IF WORK IS TERMINATED BEFORE COMPLETION (IERR = -2)         */
/*     THE FIRST N*NBLOCK ELEMENTS OF WORK CONTAIN THE BEST VECTORS     */
/*     FOR RESTARTING THE ALGORITHM AND SNLASO CAN BE IMMEDIATELY       */
/*     RECALLED TO CONTINUE WORKING ON THE PROBLEM.                     */
/*                                                                      */
/*   IND   IND(1)  CONTAINS THE ACTUAL NUMBER OF CALLS TO OP.  ON SOME  */
/*     OCCASIONS THE NUMBER OF CALLS TO OP MAY BE SLIGHTLY LARGER       */
/*     THAN MAXOP.                                                      */
/*                                                                      */
/*   IERR   AN ERROR COMPLETION CODE.  THE NORMAL COMPLETION CODE IS    */
/*     ZERO.  SEE THE DOCUMENTATION FOR INTERPRETATIONS OF NON-ZERO     */
/*     COMPLETION CODES.                                                */
/*                                                                      */
/* INTERNAL VARIABLES.                                                  */
/*                                                                      */
/* NOP   RETURNED FROM SNWLA AS THE NUMBER OF CALLS TO THE              */
/*   SUBROUTINE OP.                                                     */
/*                                                                      */
/* NV   SET EQUAL TO ABS(NVAL), THE NUMBER OF EIGENVALUES DESIRED,      */
/*   AND PASSED TO SNWLA.                                               */
/*                                                                      */
/* SMALL   SET TO .TRUE. IF THE SMALLEST EIGENVALUES ARE DESIRED.       */
/*                                                                      */
/* RARITZ   RETURNED FROM SNWLA AND PASSED TO SNPPLA.  RARITZ IS .TRUE. */
/*   IF A FINAL RAYLEIGH-RITZ PROCEDURE IS NEEDED.                      */
/*                                                                      */
/* DELTA   RETURNED FROM SNWLA AS THE EIGENVALUE OF THE MATRIX          */
/*   WHICH IS CLOSEST TO THE DESIRED EIGENVALUES.                       */
/*                                                                      */
/* SNPPLA   A SUBROUTINE FOR POST-PROCESSING THE EIGENVECTORS COMPUTED  */
/*   BY SNWLA.                                                          */
/*                                                                      */
/* SNWLA   A SUBROUTINE FOR IMPLEMENTING THE LANCZOS ALGORITHM          */
/*   WITH SELECTIVE ORTHOGONALIZATION.                                  */
/*                                                                      */
/* SMVPC   A SUBROUTINE FOR COMPUTING THE RESIDUAL NORM AND             */
/*   ORTHOGONALITY COEFFICIENT OF GIVEN RITZ VECTORS.                   */
/*                                                                      */
/* SORTQR   A SUBROUTINE FOR ORTHONORMALIZING A BLOCK OF VECTORS        */
/*   USING HOUSEHOLDER REFLECTIONS.                                     */
/*                                                                      */
/* SAXPY,SCOPY,SDOT,SNRM2,SSCAL,SSWAP   A SUBSET OF THE BASIC LINEAR    */
/*   ALGEBRA SUBPROGRAMS USED FOR VECTOR MANIPULATION.                  */
/*                                                                      */
/* SLARAN   A SUBROUTINE TO GENERATE RANDOM VECTORS                     */
/*                                                                      */
/* SLAEIG, SLAGER, SLABCM, SLABFC   SUBROUTINES FOR BAND EIGENVALUE     */
/*   CALCULATIONS.                                                      */
/*                                                                      */
/* ------------------------------------------------------------------   */

/* THIS SECTION CHECKS FOR INCONSISTENCY IN THE INPUT PARAMETERS. */

    nv = abs(*nval);
    ind[0] = 0;
    *ierr = 0;
    if (*n < *nblock * 6) {
        *ierr = 1;
    }
    if (*nfig <= 0) {
        *ierr += 2;
    }
    if (*nmvec < *n) {
        *ierr += 4;
    }
    if (*nperm < 0) {
        *ierr += 8;
    }
    if (*maxj < *nblock * 6) {
        *ierr += 16;
    }
    if (nv < max(1,*nperm)) {
        *ierr += 32;
    }
    if (nv > *nmval) {
        *ierr += 64;
    }
    if (nv > *maxop) {
        *ierr += 128;
    }
    if (nv >= *maxj / 2) {
        *ierr += 256;
    }
    if (*nblock < 1) {
        *ierr += 512;
    }
    if (*ierr != 0) {
        return;
    }

    small = *nval < 0;

/* ------------------------------------------------------------------ */

/* THIS SECTION SORTS AND ORTHONORMALIZES THE USER SUPPLIED VECTORS. */
/* IF A USER SUPPLIED VECTOR IS ZERO OR IF SIGNIFICANT CANCELLATION  */
/* OCCURS IN THE ORTHOGONALIZATION PROCESS THEN IERR IS SET TO  -1   */
/* AND SNLASO TERMINATES. */

    if (*nperm == 0) {
        goto L110;
    }

/* THIS NEGATES THE USER SUPPLIED EIGENVALUES WHEN THE LARGEST */
/* EIGENVALUES ARE DESIRED, SINCE SNWLA WILL IMPLICITLY USE THE */
/* NEGATIVE OF THE MATRIX. */

    if (!small)
    for (i = 0; i < *nperm; ++i) {
        val[i] = -val[i];
    }

/* THIS SORTS THE USER SUPPLIED VALUES AND VECTORS. */

    svsort_(nperm, val, &val[*nmval], &c__0, &tarr, nmvec, n, vec);

/* THIS STORES THE NORMS OF THE VECTORS FOR LATER COMPARISON. */
/* IT ALSO INSURES THAT THE RESIDUAL NORMS ARE POSITIVE. */

    for (i = 0; i < *nperm; ++i) {
        val[i + *nmval] = abs(val[i + *nmval]);
        val[i + *nmval * 2] = snrm2_(n, &vec[i * *nmvec], &c__1);
    }

/* THIS PERFORMS THE ORTHONORMALIZATION. */

    m = *n * *nblock;
    sortqr_(nmvec, n, nperm, vec, &work[m]);
    for (i = 0; i < *nperm; ++i, m += *nperm + 1) {
        if (abs(work[m]) <= val[i + *nmval * 2] * .9f) {
            *ierr = -1;
            return;
        }
    }

/* THIS COPIES THE RESIDUAL NORMS INTO THE CORRECT LOCATIONS IN */
/* THE ARRAY WORK FOR LATER REFERENCE IN SNWLA. */

    m = (*n << 1) * *nblock;
    scopy_(nperm, &val[*nmval], &c__1, &work[m], &c__1);

/* THIS SETS EPS TO AN APPROXIMATION OF THE RELATIVE MACHINE */
/* PRECISION */

/* ***THIS SHOULD BE REPLACED BY AN ASSIGNMENT STATEMENT */
/* ***IN A PRODUCTION CODE */

L110:
    eps = 1.f;
    for (i = 0; i < 1000; ++i) {
        eps *= .5f;
        temp = eps + 1.f;
        if (temp == 1.f) {
            break;
        }
    }

/* ------------------------------------------------------------------ */

/* THIS SECTION CALLS SNWLA WHICH IMPLEMENTS THE LANCZOS ALGORITHM */
/* WITH SELECTIVE ORTHOGONALIZATION. */

    nband = *nblock + 1;
    i1 = *n * *nblock;
    i2 = i1 + *n * *nblock;
    i3 = i2 + nv;
    i4 = i3 + nv;
    i5 = i4 + nv;
    i6 = i5 + *maxj * nband;
    i7 = i6 + *nblock * *nblock;
    i8 = i7 + *nblock * *nblock;
    i9 = i8 + *maxj * (nv + 1);
    i10 = i9 + *nblock;
    i11 = i10 + (nv << 1) + 6;
    i12 = i11 + *maxj * ((*nblock << 1) + 1);
    i13 = i12 + *maxj;
    snwla_(op, iovect, n, &nband, &nv, nfig, nperm, val, nmvec, vec, nblock,
           maxop, maxj, &nop, work, &work[i1], &work[i2], &work[i3], &work[i4],
           &work[i5], &work[i6], &work[i7], &work[i8], &work[i9], &work[i10],
           &work[i11], &work[i12], &work[i13], ind, &small, &raritz, &delta, &eps, ierr);

/* ------------------------------------------------------------------ */

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