---
name: "zpttrsv"
section: "3"
platform: "linux"
package: "scalapack-doc"
version: "1.5-11"
release: "Debian 11 (Bullseye)"
platforms: ["linux"]
url: "https://new.carta.tech/zpttrsv"
---

# zpttrsv(3)

solve one of the triangular systems L \* X = B, or L\*\*H \* X = B,

## NAME

ZPTTRSV - solve one of the triangular systems  L \* X = B, or L\*\*H \* X = B,

## SYNOPSIS

- SUBROUTINE ZPTTRSV(

  UPLO, TRANS, N, NRHS, D, E, B, LDB, INFO )

- CHARACTER

  UPLO, TRANS

- INTEGER

  INFO, LDB, N, NRHS

- DOUBLE

  PRECISION D( \* )

- COMPLEX\*16

  B( LDB, \* ), E( \* )

## PURPOSE

ZPTTRSV solves one of the triangular 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 definite tridiagonal matrix A such that\
 A = U\*\*H\*D\*U or A = L\*D\*L\*\*H (computed by ZPTTRF).\

## ARGUMENTS

- UPLO (input) CHARACTER\*1

  Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A is stored and the form 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) INTEGER

  The order of the tridiagonal 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.

- D (input) REAL array, dimension (N)

  The n diagonal elements of the diagonal matrix D from the factorization computed by ZPTTRF.

- E (input) COMPLEX array, dimension (N-1)

  The (n-1) off-diagonal elements of the unit bidiagonal factor U or L from the factorization computed by ZPTTRF (see UPLO).

- B (input/output) COMPLEX array, dimension (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) INTEGER

  \= 0:  successful exit\
   \< 0:  if INFO = -i, the i-th argument had an illegal value