stbtrs.c
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00001 /* stbtrs.f -- translated by f2c (version 20061008).
00002    You must link the resulting object file with libf2c:
00003         on Microsoft Windows system, link with libf2c.lib;
00004         on Linux or Unix systems, link with .../path/to/libf2c.a -lm
00005         or, if you install libf2c.a in a standard place, with -lf2c -lm
00006         -- in that order, at the end of the command line, as in
00007                 cc *.o -lf2c -lm
00008         Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
00009 
00010                 http://www.netlib.org/f2c/libf2c.zip
00011 */
00012 
00013 #include "f2c.h"
00014 #include "blaswrap.h"
00015 
00016 /* Table of constant values */
00017 
00018 static integer c__1 = 1;
00019 
00020 /* Subroutine */ int stbtrs_(char *uplo, char *trans, char *diag, integer *n, 
00021         integer *kd, integer *nrhs, real *ab, integer *ldab, real *b, integer 
00022         *ldb, integer *info)
00023 {
00024     /* System generated locals */
00025     integer ab_dim1, ab_offset, b_dim1, b_offset, i__1;
00026 
00027     /* Local variables */
00028     integer j;
00029     extern logical lsame_(char *, char *);
00030     logical upper;
00031     extern /* Subroutine */ int stbsv_(char *, char *, char *, integer *, 
00032             integer *, real *, integer *, real *, integer *), xerbla_(char *, integer *);
00033     logical nounit;
00034 
00035 
00036 /*  -- LAPACK routine (version 3.2) -- */
00037 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00038 /*     November 2006 */
00039 
00040 /*     .. Scalar Arguments .. */
00041 /*     .. */
00042 /*     .. Array Arguments .. */
00043 /*     .. */
00044 
00045 /*  Purpose */
00046 /*  ======= */
00047 
00048 /*  STBTRS solves a triangular system of the form */
00049 
00050 /*     A * X = B  or  A**T * X = B, */
00051 
00052 /*  where A is a triangular band matrix of order N, and B is an */
00053 /*  N-by NRHS matrix.  A check is made to verify that A is nonsingular. */
00054 
00055 /*  Arguments */
00056 /*  ========= */
00057 
00058 /*  UPLO    (input) CHARACTER*1 */
00059 /*          = 'U':  A is upper triangular; */
00060 /*          = 'L':  A is lower triangular. */
00061 
00062 /*  TRANS   (input) CHARACTER*1 */
00063 /*          Specifies the form the system of equations: */
00064 /*          = 'N':  A * X = B  (No transpose) */
00065 /*          = 'T':  A**T * X = B  (Transpose) */
00066 /*          = 'C':  A**H * X = B  (Conjugate transpose = Transpose) */
00067 
00068 /*  DIAG    (input) CHARACTER*1 */
00069 /*          = 'N':  A is non-unit triangular; */
00070 /*          = 'U':  A is unit triangular. */
00071 
00072 /*  N       (input) INTEGER */
00073 /*          The order of the matrix A.  N >= 0. */
00074 
00075 /*  KD      (input) INTEGER */
00076 /*          The number of superdiagonals or subdiagonals of the */
00077 /*          triangular band matrix A.  KD >= 0. */
00078 
00079 /*  NRHS    (input) INTEGER */
00080 /*          The number of right hand sides, i.e., the number of columns */
00081 /*          of the matrix B.  NRHS >= 0. */
00082 
00083 /*  AB      (input) REAL array, dimension (LDAB,N) */
00084 /*          The upper or lower triangular band matrix A, stored in the */
00085 /*          first kd+1 rows of AB.  The j-th column of A is stored */
00086 /*          in the j-th column of the array AB as follows: */
00087 /*          if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; */
00088 /*          if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd). */
00089 /*          If DIAG = 'U', the diagonal elements of A are not referenced */
00090 /*          and are assumed to be 1. */
00091 
00092 /*  LDAB    (input) INTEGER */
00093 /*          The leading dimension of the array AB.  LDAB >= KD+1. */
00094 
00095 /*  B       (input/output) REAL array, dimension (LDB,NRHS) */
00096 /*          On entry, the right hand side matrix B. */
00097 /*          On exit, if INFO = 0, the solution matrix X. */
00098 
00099 /*  LDB     (input) INTEGER */
00100 /*          The leading dimension of the array B.  LDB >= max(1,N). */
00101 
00102 /*  INFO    (output) INTEGER */
00103 /*          = 0:  successful exit */
00104 /*          < 0:  if INFO = -i, the i-th argument had an illegal value */
00105 /*          > 0:  if INFO = i, the i-th diagonal element of A is zero, */
00106 /*                indicating that the matrix is singular and the */
00107 /*                solutions X have not been computed. */
00108 
00109 /*  ===================================================================== */
00110 
00111 /*     .. Parameters .. */
00112 /*     .. */
00113 /*     .. Local Scalars .. */
00114 /*     .. */
00115 /*     .. External Functions .. */
00116 /*     .. */
00117 /*     .. External Subroutines .. */
00118 /*     .. */
00119 /*     .. Intrinsic Functions .. */
00120 /*     .. */
00121 /*     .. Executable Statements .. */
00122 
00123 /*     Test the input parameters. */
00124 
00125     /* Parameter adjustments */
00126     ab_dim1 = *ldab;
00127     ab_offset = 1 + ab_dim1;
00128     ab -= ab_offset;
00129     b_dim1 = *ldb;
00130     b_offset = 1 + b_dim1;
00131     b -= b_offset;
00132 
00133     /* Function Body */
00134     *info = 0;
00135     nounit = lsame_(diag, "N");
00136     upper = lsame_(uplo, "U");
00137     if (! upper && ! lsame_(uplo, "L")) {
00138         *info = -1;
00139     } else if (! lsame_(trans, "N") && ! lsame_(trans, 
00140             "T") && ! lsame_(trans, "C")) {
00141         *info = -2;
00142     } else if (! nounit && ! lsame_(diag, "U")) {
00143         *info = -3;
00144     } else if (*n < 0) {
00145         *info = -4;
00146     } else if (*kd < 0) {
00147         *info = -5;
00148     } else if (*nrhs < 0) {
00149         *info = -6;
00150     } else if (*ldab < *kd + 1) {
00151         *info = -8;
00152     } else if (*ldb < max(1,*n)) {
00153         *info = -10;
00154     }
00155     if (*info != 0) {
00156         i__1 = -(*info);
00157         xerbla_("STBTRS", &i__1);
00158         return 0;
00159     }
00160 
00161 /*     Quick return if possible */
00162 
00163     if (*n == 0) {
00164         return 0;
00165     }
00166 
00167 /*     Check for singularity. */
00168 
00169     if (nounit) {
00170         if (upper) {
00171             i__1 = *n;
00172             for (*info = 1; *info <= i__1; ++(*info)) {
00173                 if (ab[*kd + 1 + *info * ab_dim1] == 0.f) {
00174                     return 0;
00175                 }
00176 /* L10: */
00177             }
00178         } else {
00179             i__1 = *n;
00180             for (*info = 1; *info <= i__1; ++(*info)) {
00181                 if (ab[*info * ab_dim1 + 1] == 0.f) {
00182                     return 0;
00183                 }
00184 /* L20: */
00185             }
00186         }
00187     }
00188     *info = 0;
00189 
00190 /*     Solve A * X = B  or  A' * X = B. */
00191 
00192     i__1 = *nrhs;
00193     for (j = 1; j <= i__1; ++j) {
00194         stbsv_(uplo, trans, diag, n, kd, &ab[ab_offset], ldab, &b[j * b_dim1 
00195                 + 1], &c__1);
00196 /* L30: */
00197     }
00198 
00199     return 0;
00200 
00201 /*     End of STBTRS */
00202 
00203 } /* stbtrs_ */


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autogenerated on Sat Jun 8 2019 18:56:14