Visible to Intel only — GUID: GUID-023D672F-3647-4C4C-9BD0-86E47EC0AA2D
Visible to Intel only — GUID: GUID-023D672F-3647-4C4C-9BD0-86E47EC0AA2D
?sytrs_3
Solves a system of linear equations A * X = B with a real or complex symmetric matrix.
call ssytrs_3(uplo, n, nrhs, A, lda, e, ipiv, B, ldb, info)
call dsytrs_3(uplo, n, nrhs, A, lda, e, ipiv, B, ldb, info)
call csytrs_3(uplo, n, nrhs, A, lda, e, ipiv, B, ldb, info)
call zsytrs_3(uplo, n, nrhs, A, lda, e, ipiv, B, ldb, info)
Description
?sytrs_3 solves a system of linear equations A * X = B with a real or complex symmetric matrix A using the factorization computed by ?sytrf_rk: A = P*U*D*(UT)*(PT) or A = P*L*D*(LT)*(PT), where U (or L) is unit upper (or lower) triangular matrix, UT (or LT) is the transpose of U (or L), P is a permutation matrix, PT is the transpose of P, and D is a symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.
This algorithm uses Level 3 BLAS.
Input Parameters
- uplo
-
CHARACTER*1
Specifies whether the details of the factorization are stored as an upper or lower triangular matrix:
- = 'U': Upper triangular; the form is A= P*U*D*(UT)*(PT).
- = 'L': Lower triangular; the form is A = P*L*D*(LT)*(PT).
- n
-
INTEGER
The order of the matrix A. n ≥ 0.
- nrhs
-
INTEGER
The number of right-hand sides; that is, the number of columns of the matrix B. nrhs ≥ 0.
- A
-
REAL for ssytrs_3
DOUBLE PRECISION for dsytrs_3
COMPLEX for csytrs_3
COMPLEX*16 for zsytrs_3
Array, dimension (lda,n). Diagonal of the block diagonal matrix D and factors U or L as computed by ?sytrf_rk:
Only diagonal elements of the symmetric block diagonal matrix D on the diagonal of A; that is, D(k,k) = A(k,k). Superdiagonal (or subdiagonal) elements of D should be provided on entry in array e.
—and—
If uplo = 'U', factor U in the superdiagonal part of A. If uplo = 'L', factor L in the subdiagonal part of A.
- lda
-
INTEGER
The leading dimension of the array A.lda ≥ max(1, n).
- e
-
REAL for ssytrs_3
DOUBLE PRECISION for dsytrs_3
COMPLEX for csytrs_3
COMPLEX*16 for zsytrs_3
Array, dimension (n). On entry, contains the superdiagonal (or subdiagonal) elements of the symmetric block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks. If uplo = 'U', e(i) = D(i-1,i),i=2:N, and e(1) is not referenced. If uplo = 'L', e(i) = D(i+1,i), i=1:N-1, and e(n) is not referenced.
NOTE:For 1-by-1 diagonal block D(k), where 1 ≤ k ≤ n, the element e(k) is not referenced in both the uplo = 'U' and uplo = 'L' cases. - ipiv
-
INTEGER
Array, dimension (n). Details of the interchanges and the block structure of D as determined by ?sytrf_rk.
- B
-
REAL for ssytrs_3
DOUBLE PRECISION for dsytrs_3
COMPLEX for csytrs_3
COMPLEX*16 for zsytrs_3
On entry, the right-hand side matrix B.
The second dimension of B must be at least max(1, nrhs).
- ldb
-
INTEGER
The leading dimension of the array B. ldb ≥ max(1, n).
Output Parameters
- B
-
REAL for ssytrs_3
DOUBLE PRECISION for dsytrs_3
COMPLEX for csytrs_3
COMPLEX*16 for zsytrs_3
On exit, the solution matrix X.
- info
-
INTEGER
- = 0: successful exit.
- < 0: If info = -i, the ith argument had an illegal value.