ssysvx - tion to a real system of linear equations A*X = B, where A is an N-by-N symmetric matrix and X and B are N-by-NRHS matrices
SUBROUTINE SSYSVX(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER*1 FACT, UPLO INTEGER N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER IPIVOT(*), WORK2(*) REAL RCOND REAL A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*) SUBROUTINE SSYSVX_64(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER*1 FACT, UPLO INTEGER*8 N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER*8 IPIVOT(*), WORK2(*) REAL RCOND REAL A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*) F95 INTERFACE SUBROUTINE SYSVX(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER(LEN=1) :: FACT, UPLO INTEGER :: N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER, DIMENSION(:) :: IPIVOT, WORK2 REAL :: RCOND REAL, DIMENSION(:) :: FERR, BERR, WORK REAL, DIMENSION(:,:) :: A, AF, B, X SUBROUTINE SYSVX_64(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER(LEN=1) :: FACT, UPLO INTEGER(8) :: N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER(8), DIMENSION(:) :: IPIVOT, WORK2 REAL :: RCOND REAL, DIMENSION(:) :: FERR, BERR, WORK REAL, DIMENSION(:,:) :: A, AF, B, X C INTERFACE #include <sunperf.h> void ssysvx(char fact, char uplo, int n, int nrhs, float *a, int lda, float *af, int ldaf, int *ipivot, float *b, int ldb, float *x, int ldx, float *rcond, float *ferr, float *berr, int *info); void ssysvx_64(char fact, char uplo, long n, long nrhs, float *a, long lda, float *af, long ldaf, long *ipivot, float *b, long ldb, float *x, long ldx, float *rcond, float *ferr, float *berr, long *info);
Oracle Solaris Studio Performance Library ssysvx(3P) NAME ssysvx - use the diagonal pivoting factorization to compute the solu- tion to a real system of linear equations A*X = B, where A is an N-by-N symmetric matrix and X and B are N-by-NRHS matrices SYNOPSIS SUBROUTINE SSYSVX(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER*1 FACT, UPLO INTEGER N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER IPIVOT(*), WORK2(*) REAL RCOND REAL A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*) SUBROUTINE SSYSVX_64(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER*1 FACT, UPLO INTEGER*8 N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER*8 IPIVOT(*), WORK2(*) REAL RCOND REAL A(LDA,*), AF(LDAF,*), B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*) F95 INTERFACE SUBROUTINE SYSVX(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER(LEN=1) :: FACT, UPLO INTEGER :: N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER, DIMENSION(:) :: IPIVOT, WORK2 REAL :: RCOND REAL, DIMENSION(:) :: FERR, BERR, WORK REAL, DIMENSION(:,:) :: A, AF, B, X SUBROUTINE SYSVX_64(FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIVOT, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LDWORK, WORK2, INFO) CHARACTER(LEN=1) :: FACT, UPLO INTEGER(8) :: N, NRHS, LDA, LDAF, LDB, LDX, LDWORK, INFO INTEGER(8), DIMENSION(:) :: IPIVOT, WORK2 REAL :: RCOND REAL, DIMENSION(:) :: FERR, BERR, WORK REAL, DIMENSION(:,:) :: A, AF, B, X C INTERFACE #include <sunperf.h> void ssysvx(char fact, char uplo, int n, int nrhs, float *a, int lda, float *af, int ldaf, int *ipivot, float *b, int ldb, float *x, int ldx, float *rcond, float *ferr, float *berr, int *info); void ssysvx_64(char fact, char uplo, long n, long nrhs, float *a, long lda, float *af, long ldaf, long *ipivot, float *b, long ldb, float *x, long ldx, float *rcond, float *ferr, float *berr, long *info); PURPOSE ssysvx uses the diagonal pivoting factorization to compute the solution to a real system of linear equations A * X = B, where A is an N-by-N symmetric matrix and X and B are N-by-NRHS matrices. Error bounds on the solution and a condition estimate are also pro- vided. The following steps are performed: 1. If FACT = 'N', the diagonal pivoting method is used to factor A. The form of the factorization is A = U * D * U**T, if UPLO = 'U', or A = L * D * L**T, if UPLO = 'L', where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. 2. If some D(i,i)=0, so that D is exactly singular, then the routine returns with INFO = i. Otherwise, the factored form of A is used to estimate the condition number of the matrix A. If the reciprocal of the condition number is less than machine precision, INFO = N+1 is returned as a warning, but the routine still goes on to solve for X and compute error bounds as described below. 3. The system of equations is solved for X using the factored form of A. 4. Iterative refinement is applied to improve the computed solution matrix and calculate error bounds and backward error estimates for it. ARGUMENTS FACT (input) Specifies whether or not the factored form of A has been sup- plied on entry. = 'F': On entry, AF and IPIVOT contain the factored form of A. AF and IPIVOT will not be modified. = 'N': The matrix A will be copied to AF and factored. UPLO (input) = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. N (input) The number of linear equations, i.e., the order of the matrix A. N >= 0. NRHS (input) The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0. A (input) The symmetric matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. LDA (input) The leading dimension of the array A. LDA >= max(1,N). AF (input or output) If FACT = 'F', then AF is an input argument and on entry con- tains the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**T or A = L*D*L**T as computed by SSYTRF. If FACT = 'N', then AF is an output argument and on exit returns the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**T or A = L*D*L**T. LDAF (input) The leading dimension of the array AF. LDAF >= max(1,N). IPIVOT (input or output) If FACT = 'F', then IPIVOT is an input argument and on entry contains details of the interchanges and the block structure of D, as determined by SSYTRF. If IPIVOT(k) > 0, then rows and columns k and IPIVOT(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. If UPLO = 'U' and IPIVOT(k) = IPIVOT(k-1) < 0, then rows and columns k-1 and -IPIVOT(k) were interchanged and D(k-1:k,k-1:k) is a 2-by-2 diagonal block. If UPLO = 'L' and IPIVOT(k) = IPIVOT(k+1) < 0, then rows and columns k+1 and -IPIVOT(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block. If FACT = 'N', then IPIVOT is an output argument and on exit contains details of the interchanges and the block structure of D, as determined by SSYTRF. B (input) The N-by-NRHS right hand side matrix B. LDB (input) The leading dimension of the array B. LDB >= max(1,N). X (output) If INFO = 0 or INFO = N+1, the N-by-NRHS solution matrix X. LDX (input) The leading dimension of the array X. LDX >= max(1,N). RCOND (output) The estimate of the reciprocal condition number of the matrix A. If RCOND is less than the machine precision (in particu- lar, if RCOND = 0), the matrix is singular to working preci- sion. This condition is indicated by a return code of INFO > 0. FERR (output) The estimated forward error bound for each solution vector X(j) (the j-th column of the solution matrix X). If XTRUE is the true solution corresponding to X(j), FERR(j) is an esti- mated upper bound for the magnitude of the largest element in (X(j) - XTRUE) divided by the magnitude of the largest ele- ment in X(j). The estimate is as reliable as the estimate for RCOND, and is almost always a slight overestimate of the true error. BERR (output) The componentwise relative backward error of each solution vector X(j) (i.e., the smallest relative change in any ele- ment of A or B that makes X(j) an exact solution). WORK (workspace) On exit, if INFO = 0, WORK(1) returns the optimal LDWORK. LDWORK (input) The length of WORK. LDWORK >= 3*N, and for best performance LDWORK >= N*NB, where NB is the optimal blocksize for SSYTRF. If LDWORK = -1, then a workspace query is assumed; the rou- tine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LDWORK is issued by XERBLA. WORK2 (workspace) dimension(N) INFO (output) = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, and i is <= N: D(i,i) is exactly zero. The factorization has been completed but the factor D is exactly singular, so the solu- tion and error bounds could not be computed. RCOND = 0 is returned. = N+1: D is nonsingular, but RCOND is less than machine precision, meaning that the matrix is singular to working precision. Nevertheless, the solution and error bounds are computed because there are a number of situations where the computed solution can be more accurate than the value of RCOND would suggest. 7 Nov 2015 ssysvx(3P)