/* -- translated by f2c (version 19940927). You must link the resulting object file with the libraries: -lf2c -lm (in that order) */ #include #include "f2c.h" /* Subroutine */ int strsv_(char *uplo, char *trans, char *diag, integer *n, real *a, integer *lda, real *x, integer *incx) { /* System generated locals */ integer a_dim1, a_offset, i__1, i__2; /* Local variables */ static integer info; static real temp; static integer i, j; static integer ix, jx, kx; static logical nounit; extern int input_error(char *, int *); /* Purpose ======= STRSV solves one of the systems of equations A*x = b, or A'*x = b, where b and x are n element vectors and A is an n by n unit, or non-unit, upper or lower triangular matrix. No test for singularity or near-singularity is included in this routine. Such tests must be performed before calling this routine. Parameters ========== UPLO - CHARACTER*1. On entry, UPLO specifies whether the matrix is an upper or lower triangular matrix as follows: UPLO = 'U' or 'u' A is an upper triangular matrix. UPLO = 'L' or 'l' A is a lower triangular matrix. Unchanged on exit. TRANS - CHARACTER*1. On entry, TRANS specifies the equations to be solved as follows: TRANS = 'N' or 'n' A*x = b. TRANS = 'T' or 't' A'*x = b. TRANS = 'C' or 'c' A'*x = b. Unchanged on exit. DIAG - CHARACTER*1. On entry, DIAG specifies whether or not A is unit triangular as follows: DIAG = 'U' or 'u' A is assumed to be unit triangular. DIAG = 'N' or 'n' A is not assumed to be unit triangular. Unchanged on exit. N - INTEGER. On entry, N specifies the order of the matrix A. N must be at least zero. Unchanged on exit. A - REAL array of DIMENSION ( LDA, n ). Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array A must contain the upper triangular matrix and the strictly lower triangular part of A is not referenced. Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular matrix and the strictly upper triangular part of A is not referenced. Note that when DIAG = 'U' or 'u', the diagonal elements of A are not referenced either, but are assumed to be unity. Unchanged on exit. LDA - INTEGER. On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least max( 1, n ). Unchanged on exit. X - REAL array of dimension at least ( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element right-hand side vector b. On exit, X is overwritten with the solution vector x. INCX - INTEGER. On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit. Level 2 Blas routine. -- Written on 22-October-1986. Jack Dongarra, Argonne National Lab. Jeremy Du Croz, Nag Central Office. Sven Hammarling, Nag Central Office. Richard Hanson, Sandia National Labs. Test the input parameters. Parameter adjustments Function Body */ #define X(I) x[(I)-1] #define A(I,J) a[(I)-1 + ((J)-1)* ( *lda)] info = 0; if ( strncmp(uplo, "U", 1)!=0 && strncmp(uplo, "L", 1)!=0 ) { info = 1; } else if ( strncmp(trans, "N", 1)!=0 && strncmp(trans, "T", 1)!=0 && strncmp(trans, "C", 1)!=0 ) { info = 2; } else if ( strncmp(diag, "U", 1)!=0 && strncmp(diag, "N", 1)!=0 ) { info = 3; } else if (*n < 0) { info = 4; } else if (*lda < max(1,*n)) { info = 6; } else if (*incx == 0) { info = 8; } if (info != 0) { input_error("STRSV ", &info); return 0; } /* Quick return if possible. */ if (*n == 0) { return 0; } nounit = (strncmp(diag, "N", 1)==0); /* Set up the start point in X if the increment is not unity. This will be ( N - 1 )*INCX too small for descending loops. */ if (*incx <= 0) { kx = 1 - (*n - 1) * *incx; } else if (*incx != 1) { kx = 1; } /* Start the operations. In this version the elements of A are accessed sequentially with one pass through A. */ if (strncmp(trans, "N", 1)==0) { /* Form x := inv( A )*x. */ if (strncmp(uplo, "U", 1)==0) { if (*incx == 1) { for (j = *n; j >= 1; --j) { if (X(j) != 0.f) { if (nounit) { X(j) /= A(j,j); } temp = X(j); for (i = j - 1; i >= 1; --i) { X(i) -= temp * A(i,j); /* L10: */ } } /* L20: */ } } else { jx = kx + (*n - 1) * *incx; for (j = *n; j >= 1; --j) { if (X(jx) != 0.f) { if (nounit) { X(jx) /= A(j,j); } temp = X(jx); ix = jx; for (i = j - 1; i >= 1; --i) { ix -= *incx; X(ix) -= temp * A(i,j); /* L30: */ } } jx -= *incx; /* L40: */ } } } else { if (*incx == 1) { i__1 = *n; for (j = 1; j <= *n; ++j) { if (X(j) != 0.f) { if (nounit) { X(j) /= A(j,j); } temp = X(j); i__2 = *n; for (i = j + 1; i <= *n; ++i) { X(i) -= temp * A(i,j); /* L50: */ } } /* L60: */ } } else { jx = kx; i__1 = *n; for (j = 1; j <= *n; ++j) { if (X(jx) != 0.f) { if (nounit) { X(jx) /= A(j,j); } temp = X(jx); ix = jx; i__2 = *n; for (i = j + 1; i <= *n; ++i) { ix += *incx; X(ix) -= temp * A(i,j); /* L70: */ } } jx += *incx; /* L80: */ } } } } else { /* Form x := inv( A' )*x. */ if (strncmp(uplo, "U", 1)==0) { if (*incx == 1) { i__1 = *n; for (j = 1; j <= *n; ++j) { temp = X(j); i__2 = j - 1; for (i = 1; i <= j-1; ++i) { temp -= A(i,j) * X(i); /* L90: */ } if (nounit) { temp /= A(j,j); } X(j) = temp; /* L100: */ } } else { jx = kx; i__1 = *n; for (j = 1; j <= *n; ++j) { temp = X(jx); ix = kx; i__2 = j - 1; for (i = 1; i <= j-1; ++i) { temp -= A(i,j) * X(ix); ix += *incx; /* L110: */ } if (nounit) { temp /= A(j,j); } X(jx) = temp; jx += *incx; /* L120: */ } } } else { if (*incx == 1) { for (j = *n; j >= 1; --j) { temp = X(j); i__1 = j + 1; for (i = *n; i >= j+1; --i) { temp -= A(i,j) * X(i); /* L130: */ } if (nounit) { temp /= A(j,j); } X(j) = temp; /* L140: */ } } else { kx += (*n - 1) * *incx; jx = kx; for (j = *n; j >= 1; --j) { temp = X(jx); ix = kx; i__1 = j + 1; for (i = *n; i >= j+1; --i) { temp -= A(i,j) * X(ix); ix -= *incx; /* L150: */ } if (nounit) { temp /= A(j,j); } X(jx) = temp; jx -= *incx; /* L160: */ } } } } return 0; /* End of STRSV . */ } /* strsv_ */