strti2.c
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00001 /* strti2.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 strti2_(char *uplo, char *diag, integer *n, real *a, 
00021         integer *lda, integer *info)
00022 {
00023     /* System generated locals */
00024     integer a_dim1, a_offset, i__1, i__2;
00025 
00026     /* Local variables */
00027     integer j;
00028     real ajj;
00029     extern logical lsame_(char *, char *);
00030     extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *);
00031     logical upper;
00032     extern /* Subroutine */ int strmv_(char *, char *, char *, integer *, 
00033             real *, integer *, real *, integer *), 
00034             xerbla_(char *, integer *);
00035     logical nounit;
00036 
00037 
00038 /*  -- LAPACK routine (version 3.2) -- */
00039 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00040 /*     November 2006 */
00041 
00042 /*     .. Scalar Arguments .. */
00043 /*     .. */
00044 /*     .. Array Arguments .. */
00045 /*     .. */
00046 
00047 /*  Purpose */
00048 /*  ======= */
00049 
00050 /*  STRTI2 computes the inverse of a real upper or lower triangular */
00051 /*  matrix. */
00052 
00053 /*  This is the Level 2 BLAS version of the algorithm. */
00054 
00055 /*  Arguments */
00056 /*  ========= */
00057 
00058 /*  UPLO    (input) CHARACTER*1 */
00059 /*          Specifies whether the matrix A is upper or lower triangular. */
00060 /*          = 'U':  Upper triangular */
00061 /*          = 'L':  Lower triangular */
00062 
00063 /*  DIAG    (input) CHARACTER*1 */
00064 /*          Specifies whether or not the matrix A is unit triangular. */
00065 /*          = 'N':  Non-unit triangular */
00066 /*          = 'U':  Unit triangular */
00067 
00068 /*  N       (input) INTEGER */
00069 /*          The order of the matrix A.  N >= 0. */
00070 
00071 /*  A       (input/output) REAL array, dimension (LDA,N) */
00072 /*          On entry, the triangular matrix A.  If UPLO = 'U', the */
00073 /*          leading n by n upper triangular part of the array A contains */
00074 /*          the upper triangular matrix, and the strictly lower */
00075 /*          triangular part of A is not referenced.  If UPLO = 'L', the */
00076 /*          leading n by n lower triangular part of the array A contains */
00077 /*          the lower triangular matrix, and the strictly upper */
00078 /*          triangular part of A is not referenced.  If DIAG = 'U', the */
00079 /*          diagonal elements of A are also not referenced and are */
00080 /*          assumed to be 1. */
00081 
00082 /*          On exit, the (triangular) inverse of the original matrix, in */
00083 /*          the same storage format. */
00084 
00085 /*  LDA     (input) INTEGER */
00086 /*          The leading dimension of the array A.  LDA >= max(1,N). */
00087 
00088 /*  INFO    (output) INTEGER */
00089 /*          = 0: successful exit */
00090 /*          < 0: if INFO = -k, the k-th argument had an illegal value */
00091 
00092 /*  ===================================================================== */
00093 
00094 /*     .. Parameters .. */
00095 /*     .. */
00096 /*     .. Local Scalars .. */
00097 /*     .. */
00098 /*     .. External Functions .. */
00099 /*     .. */
00100 /*     .. External Subroutines .. */
00101 /*     .. */
00102 /*     .. Intrinsic Functions .. */
00103 /*     .. */
00104 /*     .. Executable Statements .. */
00105 
00106 /*     Test the input parameters. */
00107 
00108     /* Parameter adjustments */
00109     a_dim1 = *lda;
00110     a_offset = 1 + a_dim1;
00111     a -= a_offset;
00112 
00113     /* Function Body */
00114     *info = 0;
00115     upper = lsame_(uplo, "U");
00116     nounit = lsame_(diag, "N");
00117     if (! upper && ! lsame_(uplo, "L")) {
00118         *info = -1;
00119     } else if (! nounit && ! lsame_(diag, "U")) {
00120         *info = -2;
00121     } else if (*n < 0) {
00122         *info = -3;
00123     } else if (*lda < max(1,*n)) {
00124         *info = -5;
00125     }
00126     if (*info != 0) {
00127         i__1 = -(*info);
00128         xerbla_("STRTI2", &i__1);
00129         return 0;
00130     }
00131 
00132     if (upper) {
00133 
00134 /*        Compute inverse of upper triangular matrix. */
00135 
00136         i__1 = *n;
00137         for (j = 1; j <= i__1; ++j) {
00138             if (nounit) {
00139                 a[j + j * a_dim1] = 1.f / a[j + j * a_dim1];
00140                 ajj = -a[j + j * a_dim1];
00141             } else {
00142                 ajj = -1.f;
00143             }
00144 
00145 /*           Compute elements 1:j-1 of j-th column. */
00146 
00147             i__2 = j - 1;
00148             strmv_("Upper", "No transpose", diag, &i__2, &a[a_offset], lda, &
00149                     a[j * a_dim1 + 1], &c__1);
00150             i__2 = j - 1;
00151             sscal_(&i__2, &ajj, &a[j * a_dim1 + 1], &c__1);
00152 /* L10: */
00153         }
00154     } else {
00155 
00156 /*        Compute inverse of lower triangular matrix. */
00157 
00158         for (j = *n; j >= 1; --j) {
00159             if (nounit) {
00160                 a[j + j * a_dim1] = 1.f / a[j + j * a_dim1];
00161                 ajj = -a[j + j * a_dim1];
00162             } else {
00163                 ajj = -1.f;
00164             }
00165             if (j < *n) {
00166 
00167 /*              Compute elements j+1:n of j-th column. */
00168 
00169                 i__1 = *n - j;
00170                 strmv_("Lower", "No transpose", diag, &i__1, &a[j + 1 + (j + 
00171                         1) * a_dim1], lda, &a[j + 1 + j * a_dim1], &c__1);
00172                 i__1 = *n - j;
00173                 sscal_(&i__1, &ajj, &a[j + 1 + j * a_dim1], &c__1);
00174             }
00175 /* L20: */
00176         }
00177     }
00178 
00179     return 0;
00180 
00181 /*     End of STRTI2 */
00182 
00183 } /* strti2_ */


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autogenerated on Sat Jun 8 2019 18:56:15