sspsv.c
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00001 /* sspsv.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 /* Subroutine */ int sspsv_(char *uplo, integer *n, integer *nrhs, real *ap, 
00017         integer *ipiv, real *b, integer *ldb, integer *info)
00018 {
00019     /* System generated locals */
00020     integer b_dim1, b_offset, i__1;
00021 
00022     /* Local variables */
00023     extern logical lsame_(char *, char *);
00024     extern /* Subroutine */ int xerbla_(char *, integer *), ssptrf_(
00025             char *, integer *, real *, integer *, integer *), ssptrs_(
00026             char *, integer *, integer *, real *, integer *, real *, integer *
00027 , integer *);
00028 
00029 
00030 /*  -- LAPACK driver routine (version 3.2) -- */
00031 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00032 /*     November 2006 */
00033 
00034 /*     .. Scalar Arguments .. */
00035 /*     .. */
00036 /*     .. Array Arguments .. */
00037 /*     .. */
00038 
00039 /*  Purpose */
00040 /*  ======= */
00041 
00042 /*  SSPSV computes the solution to a real system of linear equations */
00043 /*     A * X = B, */
00044 /*  where A is an N-by-N symmetric matrix stored in packed format and X */
00045 /*  and B are N-by-NRHS matrices. */
00046 
00047 /*  The diagonal pivoting method is used to factor A as */
00048 /*     A = U * D * U**T,  if UPLO = 'U', or */
00049 /*     A = L * D * L**T,  if UPLO = 'L', */
00050 /*  where U (or L) is a product of permutation and unit upper (lower) */
00051 /*  triangular matrices, D is symmetric and block diagonal with 1-by-1 */
00052 /*  and 2-by-2 diagonal blocks.  The factored form of A is then used to */
00053 /*  solve the system of equations A * X = B. */
00054 
00055 /*  Arguments */
00056 /*  ========= */
00057 
00058 /*  UPLO    (input) CHARACTER*1 */
00059 /*          = 'U':  Upper triangle of A is stored; */
00060 /*          = 'L':  Lower triangle of A is stored. */
00061 
00062 /*  N       (input) INTEGER */
00063 /*          The number of linear equations, i.e., the order of the */
00064 /*          matrix A.  N >= 0. */
00065 
00066 /*  NRHS    (input) INTEGER */
00067 /*          The number of right hand sides, i.e., the number of columns */
00068 /*          of the matrix B.  NRHS >= 0. */
00069 
00070 /*  AP      (input/output) REAL array, dimension (N*(N+1)/2) */
00071 /*          On entry, the upper or lower triangle of the symmetric matrix */
00072 /*          A, packed columnwise in a linear array.  The j-th column of A */
00073 /*          is stored in the array AP as follows: */
00074 /*          if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; */
00075 /*          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. */
00076 /*          See below for further details. */
00077 
00078 /*          On exit, the block diagonal matrix D and the multipliers used */
00079 /*          to obtain the factor U or L from the factorization */
00080 /*          A = U*D*U**T or A = L*D*L**T as computed by SSPTRF, stored as */
00081 /*          a packed triangular matrix in the same storage format as A. */
00082 
00083 /*  IPIV    (output) INTEGER array, dimension (N) */
00084 /*          Details of the interchanges and the block structure of D, as */
00085 /*          determined by SSPTRF.  If IPIV(k) > 0, then rows and columns */
00086 /*          k and IPIV(k) were interchanged, and D(k,k) is a 1-by-1 */
00087 /*          diagonal block.  If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, */
00088 /*          then rows and columns k-1 and -IPIV(k) were interchanged and */
00089 /*          D(k-1:k,k-1:k) is a 2-by-2 diagonal block.  If UPLO = 'L' and */
00090 /*          IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and */
00091 /*          -IPIV(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 */
00092 /*          diagonal block. */
00093 
00094 /*  B       (input/output) REAL array, dimension (LDB,NRHS) */
00095 /*          On entry, the N-by-NRHS right hand side matrix B. */
00096 /*          On exit, if INFO = 0, the N-by-NRHS solution matrix X. */
00097 
00098 /*  LDB     (input) INTEGER */
00099 /*          The leading dimension of the array B.  LDB >= max(1,N). */
00100 
00101 /*  INFO    (output) INTEGER */
00102 /*          = 0:  successful exit */
00103 /*          < 0:  if INFO = -i, the i-th argument had an illegal value */
00104 /*          > 0:  if INFO = i, D(i,i) is exactly zero.  The factorization */
00105 /*                has been completed, but the block diagonal matrix D is */
00106 /*                exactly singular, so the solution could not be */
00107 /*                computed. */
00108 
00109 /*  Further Details */
00110 /*  =============== */
00111 
00112 /*  The packed storage scheme is illustrated by the following example */
00113 /*  when N = 4, UPLO = 'U': */
00114 
00115 /*  Two-dimensional storage of the symmetric matrix A: */
00116 
00117 /*     a11 a12 a13 a14 */
00118 /*         a22 a23 a24 */
00119 /*             a33 a34     (aij = aji) */
00120 /*                 a44 */
00121 
00122 /*  Packed storage of the upper triangle of A: */
00123 
00124 /*  AP = [ a11, a12, a22, a13, a23, a33, a14, a24, a34, a44 ] */
00125 
00126 /*  ===================================================================== */
00127 
00128 /*     .. External Functions .. */
00129 /*     .. */
00130 /*     .. External Subroutines .. */
00131 /*     .. */
00132 /*     .. Intrinsic Functions .. */
00133 /*     .. */
00134 /*     .. Executable Statements .. */
00135 
00136 /*     Test the input parameters. */
00137 
00138     /* Parameter adjustments */
00139     --ap;
00140     --ipiv;
00141     b_dim1 = *ldb;
00142     b_offset = 1 + b_dim1;
00143     b -= b_offset;
00144 
00145     /* Function Body */
00146     *info = 0;
00147     if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) {
00148         *info = -1;
00149     } else if (*n < 0) {
00150         *info = -2;
00151     } else if (*nrhs < 0) {
00152         *info = -3;
00153     } else if (*ldb < max(1,*n)) {
00154         *info = -7;
00155     }
00156     if (*info != 0) {
00157         i__1 = -(*info);
00158         xerbla_("SSPSV ", &i__1);
00159         return 0;
00160     }
00161 
00162 /*     Compute the factorization A = U*D*U' or A = L*D*L'. */
00163 
00164     ssptrf_(uplo, n, &ap[1], &ipiv[1], info);
00165     if (*info == 0) {
00166 
00167 /*        Solve the system A*X = B, overwriting B with X. */
00168 
00169         ssptrs_(uplo, n, nrhs, &ap[1], &ipiv[1], &b[b_offset], ldb, info);
00170 
00171     }
00172     return 0;
00173 
00174 /*     End of SSPSV */
00175 
00176 } /* sspsv_ */


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autogenerated on Sat Jun 8 2019 18:56:13