CPTTRSV ‐ solve one of the triangular systems L * X = B, or L**H
* X = B, SUBROUTINE CPTTRSV( UPLO, TRANS, N, NRHS, D, E, B, LDB,
INFO )
CHARACTER UPLO, TRANS
INTEGER INFO, LDB, N, NRHS
REAL D( * )
COMPLEX B( LDB, * ), E( * ) CPTTRSV solves one of the trian‐
gular systems L * X = B, or L**H * X = B, U * X = B, or U**H
* X = B,
where L or U is the Cholesky factor of a Hermitian positive defi‐
nite tridiagonal matrix A such thatA = U**H*D*U or A = L*D*L**H (computed by CPTTRF).
UPLO (input) CHARACTER*1 Specifies whether the superdiagonal
or the subdiagonal of the tridiagonal matrix A is stored and theform of the factorization:
= ’U’: E is the superdiagonal of U, and A = U’*D*U;
= ’L’: E is the subdiagonal of L, and A = L*D*L’. (The two
forms are equivalent if A is real.) TRANS (input) CHARACTER
Specifies the form of the system of equations:
= ’N’: L * X = B (No transpose)
= ’N’: L * X = B (No transpose)
= ’C’: U**H * X = B (Conjugate transpose)
= ’C’: L**H * X = B (Conjugate transpose) N (input) INTE‐
GER The order of the tridiagonal matrix A. N >= 0. NRHS (in‐
put) INTEGER The number of right hand sides, i.e., the number of
columns of the matrix B. NRHS >= 0. D (input) REAL array,
dimension (N) The n diagonal elements of the diagonal matrix D
from the factorization computed by CPTTRF. E (input) COM‐
PLEX array, dimension (N‐1) The (n‐1) off‐diagonal elements of
the unit bidiagonal factor U or L from the factorization computedby CPTTRF (see UPLO). B (input/output) COMPLEX array, di‐
mension (LDB,NRHS) On entry, the right hand side matrix B. On
exit, the solution matrix X. LDB (input) INTEGER The leading
dimension of the array B. LDB >= max(1,N). INFO (output) IN‐
TEGER = 0: successful exit
< 0: if INFO = ‐i, the i‐th argument had an illegal value
