solves a triangular system of the form A * X = B or A**T * X = B,
- SUBROUTINE STPTRS(
UPLO, TRANS, DIAG, N, NRHS, AP, B, LDB, INFO )
DIAG, TRANS, UPLO
INFO, LDB, N, NRHS
AP( * ), B( LDB, * )
STPTRS solves a triangular system of the form
where A is a triangular matrix of order N stored in packed format,
and B is an N-by-NRHS matrix. A check is made to verify that A is
- UPLO (input) CHARACTER*1
= 'U': A is upper triangular;
= 'L': A is lower triangular.
- TRANS (input) CHARACTER*1
Specifies the form of the system of equations:
= 'N': A * X = B (No transpose)
= 'T': A**T * X = B (Transpose)
= 'C': A**H * X = B (Conjugate transpose = Transpose)
- 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.
- NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 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)*(2*n-j)/2) = A(i,j) for j<=i<=n.
- B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.
On exit, if INFO = 0, the solution matrix X.
- LDB (input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
- INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the i-th diagonal element of A is zero,
indicating that the matrix is singular and the
solutions X have not been computed.