#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int stpcon_(char *norm, char *uplo, char *diag, integer *n, real *ap, real *rcond, real *work, integer *iwork, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Modified to call SLACN2 in place of SLACON, 7 Feb 03, SJH. Purpose ======= STPCON estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1-norm or the infinity-norm. The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed as RCOND = 1 / ( norm(A) * norm(inv(A)) ). Arguments ========= NORM (input) CHARACTER*1 Specifies whether the 1-norm condition number or the infinity-norm condition number is required: = '1' or 'O': 1-norm; = 'I': Infinity-norm. UPLO (input) CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular. DIAG (input) CHARACTER*1 = 'N': A is non-unit triangular; = 'U': A is unit triangular. N (input) INTEGER The order of the matrix A. N >= 0. AP (input) REAL array, dimension (N*(N+1)/2) The upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1. RCOND (output) REAL The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))). WORK (workspace) REAL array, dimension (3*N) IWORK (workspace) INTEGER array, dimension (N) INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value ===================================================================== Test the input parameters. Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; /* System generated locals */ integer i__1; real r__1; /* Local variables */ static integer ix, kase, kase1; static real scale; extern logical lsame_(char *, char *); static integer isave[3]; static real anorm; extern /* Subroutine */ int srscl_(integer *, real *, real *, integer *); static logical upper; static real xnorm; extern /* Subroutine */ int slacn2_(integer *, real *, real *, integer *, real *, integer *, integer *); extern doublereal slamch_(char *); extern /* Subroutine */ int xerbla_(char *, integer *); extern integer isamax_(integer *, real *, integer *); static real ainvnm; static logical onenrm; extern doublereal slantp_(char *, char *, char *, integer *, real *, real *); static char normin[1]; extern /* Subroutine */ int slatps_(char *, char *, char *, char *, integer *, real *, real *, real *, real *, integer *); static real smlnum; static logical nounit; --iwork; --work; --ap; /* Function Body */ *info = 0; upper = lsame_(uplo, "U"); onenrm = *(unsigned char *)norm == '1' || lsame_(norm, "O"); nounit = lsame_(diag, "N"); if (! onenrm && ! lsame_(norm, "I")) { *info = -1; } else if (! upper && ! lsame_(uplo, "L")) { *info = -2; } else if (! nounit && ! lsame_(diag, "U")) { *info = -3; } else if (*n < 0) { *info = -4; } if (*info != 0) { i__1 = -(*info); xerbla_("STPCON", &i__1); return 0; } /* Quick return if possible */ if (*n == 0) { *rcond = 1.f; return 0; } *rcond = 0.f; smlnum = slamch_("Safe minimum") * (real) max(1,*n); /* Compute the norm of the triangular matrix A. */ anorm = slantp_(norm, uplo, diag, n, &ap[1], &work[1]); /* Continue only if ANORM > 0. */ if (anorm > 0.f) { /* Estimate the norm of the inverse of A. */ ainvnm = 0.f; *(unsigned char *)normin = 'N'; if (onenrm) { kase1 = 1; } else { kase1 = 2; } kase = 0; L10: slacn2_(n, &work[*n + 1], &work[1], &iwork[1], &ainvnm, &kase, isave); if (kase != 0) { if (kase == kase1) { /* Multiply by inv(A). */ slatps_(uplo, "No transpose", diag, normin, n, &ap[1], &work[ 1], &scale, &work[(*n << 1) + 1], info); } else { /* Multiply by inv(A'). */ slatps_(uplo, "Transpose", diag, normin, n, &ap[1], &work[1], &scale, &work[(*n << 1) + 1], info); } *(unsigned char *)normin = 'Y'; /* Multiply by 1/SCALE if doing so will not cause overflow. */ if (scale != 1.f) { ix = isamax_(n, &work[1], &c__1); xnorm = (r__1 = work[ix], dabs(r__1)); if (scale < xnorm * smlnum || scale == 0.f) { goto L20; } srscl_(n, &scale, &work[1], &c__1); } goto L10; } /* Compute the estimate of the reciprocal condition number. */ if (ainvnm != 0.f) { *rcond = 1.f / anorm / ainvnm; } } L20: return 0; /* End of STPCON */ } /* stpcon_ */