complex16HEsolve(3)

📦
version 3.11.0 · 2 versions
, in debian bookworm

💖 complex16HEsolve — LAPACK 💖

okay so bestie, welcome to complex16HEsolve(3), the LAPACK page that's literally a whole friend group of complex16 solve drivers. it's giving ✨main character energy✨ and it comes in SIX parts, so buckle up, we're only doing part one rn 💅

🌸 NAME 🌸

complex16HEsolve — complex16 🦋

✨ SYNOPSIS ✨

🫶 Functions

subroutine zhesv

subroutine zhesv (UPLO, N, NRHS, A, LDA, IPIV, B, LDB, WORK, LWORK, INFO)

ZHESV computes the solution to system of linear equations A * X = B for HE matrices

subroutine zhesv_aa

subroutine zhesv_aa (UPLO, N, NRHS, A, LDA, IPIV, B, LDB, WORK, LWORK, INFO)

ZHESV_AA computes the solution to system of linear equations A * X = B for HE matrices

subroutine zhesv_aa_2stage

subroutine zhesv_aa_2stage (UPLO, N, NRHS, A, LDA, TB, LTB, IPIV, IPIV2, B, LDB, WORK, LWORK, INFO)

ZHESV_AA_2STAGE computes the solution to system of linear equations A * X = B for HE matrices

subroutine zhesv_rk

subroutine zhesv_rk (UPLO, N, NRHS, A, LDA, E, IPIV, B, LDB, WORK, LWORK, INFO)

ZHESV_RK computes the solution to system of linear equations A * X = B for SY matrices

subroutine zhesv_rook

subroutine zhesv_rook (UPLO, N, NRHS, A, LDA, IPIV, B, LDB, WORK, LWORK, INFO)

ZHESV_ROOK computes the solution to a system of linear equations A * X = B for HE matrices using the bounded Bunch-Kaufman ('rook') diagonal pivoting method

subroutine zhesvx

subroutine zhesvx (FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIV, B, LDB, X, LDX, RCOND, FERR, BERR, WORK, LWORK, RWORK, INFO)

ZHESVX computes the solution to system of linear equations A * X = B for HE matrices

subroutine zhesvxx

subroutine zhesvxx (FACT, UPLO, N, NRHS, A, LDA, AF, LDAF, IPIV, EQUED, S, B, LDB, X, LDX, RCOND, RPVGRW, BERR, N_ERR_BNDS, ERR_BNDS_NORM, ERR_BNDS_COMP, NPARAMS, PARAMS, WORK, RWORK, INFO)

ZHESVXX computes the solution to system of linear equations A * X = B for HE matrices

💫 Detailed Description 💫

no cap, this is just the whole squad of complex16 solve driver functions for HE matrices. the entire group chat 🫶

🔥 Function Documentation 🔥

💅 subroutine zhesv

subroutine zhesv (character UPLO, integer N, integer NRHS, complex*16,
    dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV,
    complex*16, dimension( ldb, * ) B, integer LDB, complex*16, dimension( *
    ) WORK, integer LWORK, integer INFO)

ZHESV computes the solution to system of linear equations A * X = B for HE matrices

🎀 Purpose

ok so ZHESV computes the solution to a complex system of linear equations

   A * X = B,

where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices. iconic behavior honestly 💖

the diagonal pivoting method is used to factor A as

   A = U * D * U**H,  if UPLO = 'U', or
   A = L * D * L**H,  if UPLO = 'L',

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. the factored form of A is then used to solve the system of equations A * X = B. slay ✨

🌟 Parameters

  • UPLO — is CHARACTER*1
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — is INTEGER. the number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — is INTEGER. the number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
  • A — is COMPLEX*16 array, dimension (LDA,N).
    • on entry, the Hermitian 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.
    • on exit, if INFO = 0, the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**H or A = L*D*L**H as computed by ZHETRF.
  • LDA — is INTEGER. the leading dimension of the array A. LDA >= max(1,N).
  • IPIV — is INTEGER array, dimension (N). details of the interchanges and the block structure of D, as determined by ZHETRF. if IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged, and D(k,k) is a 1-by-1 diagonal block. if UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) is a 2-by-2 diagonal block. if UPLO = 'L' and IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block. it's giving bookkeeping 💀
  • B — is COMPLEX*16 array, dimension (LDB,NRHS).
    • on entry, the N-by-NRHS right hand side matrix B.
    • on exit, if INFO = 0, the N-by-NRHS solution matrix X.
  • LDB — is INTEGER. the leading dimension of the array B. LDB >= max(1,N).
  • WORK — is COMPLEX*16 array, dimension (MAX(1,LWORK)). on exit, if INFO = 0, WORK(1) returns the optimal LWORK.
  • LWORK — is INTEGER. the length of WORK. LWORK >= 1, and for best performance LWORK >= max(1,N*NB), where NB is the optimal blocksize for ZHETRF.
    • for LWORK < N, TRS will be done with Level BLAS 2
    • for LWORK >= N, TRS will be done with Level BLAS 3

if LWORK = -1, then a workspace query is assumed; the routine 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 LWORK is issued by XERBLA. so don't come for it 🫶

  • INFO — is INTEGER
    • = 0: successful exit ✨
    • < 0: if INFO = -i, the i-th argument had an illegal value 😭
    • > 0: if INFO = i, D(i,i) is exactly zero. the factorization has been completed, but the block diagonal matrix D is exactly singular, so the solution could not be computed. 💀

👑 Author

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

💅 subroutine zhesv_aa

subroutine zhesv_aa (character UPLO, integer N, integer NRHS, complex*16,
    dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV,
    complex*16, dimension( ldb, * ) B, integer LDB, complex*16, dimension( *
    ) WORK, integer LWORK, integer INFO)

ZHESV_AA computes the solution to system of linear equations A * X = B for HE matrices

🎀 Purpose

ZHESV_AA computes the solution to a complex system of linear equations

   A * X = B,

where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices. same vibe, different algorithm 🦋

Aasen's algorithm is used to factor A as

   A = U**H * T * U,  if UPLO = 'U', or
   A = L * T * L**H,  if UPLO = 'L',

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and T is Hermitian and tridiagonal. the factored form of A is then used to solve the system of equations A * X = B. periodt 💅

🌟 Parameters

  • UPLO — is CHARACTER*1
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — is INTEGER. the number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — is INTEGER. the number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
  • A — is COMPLEX*16 array, dimension (LDA,N).
    • on entry, the Hermitian 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.
    • on exit, if INFO = 0, the tridiagonal matrix T and the multipliers used to obtain the factor U or L from the factorization A = U**H*T*U or A = L*T*L**H as computed by ZHETRF_AA.
  • LDA — is INTEGER. the leading dimension of the array A. LDA >= max(1,N).
  • IPIV — is INTEGER array, dimension (N). on exit, it contains the details of the interchanges, i.e., the row and column k of A were interchanged with the row and column IPIV(k). noted 📝
  • B — is COMPLEX*16 array, dimension (LDB,NRHS).
    • on entry, the N-by-NRHS right hand side matrix B.
    • on exit, if INFO = 0, the N-by-NRHS solution matrix X.
  • LDB — is INTEGER. the leading dimension of the array B. LDB >= max(1,N).
  • WORK — is COMPLEX*16 array, dimension (MAX(1,LWORK)). on exit, if INFO = 0, WORK(1) returns the optimal LWORK.
  • LWORK — is INTEGER. the length of WORK. LWORK >= MAX(1,2*N,3*N-2), and for best performance LWORK >= max(1,N*NB), where NB is the optimal blocksize for ZHETRF. (yes bestie, this one wants a bigger workspace than plain old ZHESV, lowkey iconic of it)

if LWORK = -1, then a workspace query is assumed; the routine 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 LWORK is issued by XERBLA.

  • INFO — is INTEGER
    • = 0: successful exit ✨
    • < 0: if INFO = -i, the i-th argument had an illegal value 😭
    • > 0: if INFO = i, D(i,i) is exactly zero. the factorization has been completed, but the block diagonal matrix D is exactly singular, so the solution could not be computed. 💀

👑 Author

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

subroutine zhesv_aa_2stage 💖

subroutine zhesv_aa_2stage (character UPLO, integer N, integer NRHS,
    complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension( *
    ) TB, integer LTB, integer, dimension( * ) IPIV, integer, dimension( * )
    IPIV2, complex*16, dimension( ldb, * ) B, integer LDB, complex*16,
    dimension( * ) WORK, integer LWORK, integer INFO)

okay so bestie, ZHESV_AA_2STAGE computes the solution to system of linear equations A * X = B for HE matrices. it's giving solver energy fr fr.

✨ Purpose ✨

so basically ZHESV_AA_2STAGE computes the solution to a complex system of linear equations

   A * X = B,

where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices. 😌

Aasen's 2-stage algorithm is used to factor A as

   A = U**H * T * U,  if UPLO = 'U', or
   A = L * T * L**H,  if UPLO = 'L',

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and T is Hermitian and band. The matrix T is then LU-factored with partial pivoting. The factored form of A is then used to solve the system of equations A * X = B.

This is the blocked version of the algorithm, calling Level 3 BLAS. level 3 blas?? we love a blocked queen 💅

🌸 Parameters 🌸

  • UPLO — UPLO is CHARACTER*1
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — N is INTEGER. The order of the matrix A. N >= 0.
  • NRHS — NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
  • A — A is COMPLEX*16 array, dimension (LDA,N). On entry, the hermitian 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. On exit, L is stored below (or above) the subdiagonal blocks, when UPLO is 'L' (or 'U'). 🦋
  • LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • TB — TB is COMPLEX*16 array, dimension (LTB). On exit, details of the LU factorization of the band matrix. 👑
  • LTB — LTB is INTEGER. The size of the array TB. LTB >= 4*N, internally used to select NB such that LTB >= (3*NB+1)*N. If LTB = -1, then a workspace query is assumed; the routine only calculates the optimal size of LTB, returns this value as the first entry of TB, and no error message related to LTB is issued by XERBLA. (yes bestie, -1 is the "just tell me how much room i need" move 🙈)
  • IPIV — IPIV is INTEGER array, dimension (N). On exit, it contains the details of the interchanges, i.e., the row and column k of A were interchanged with the row and column IPIV(k).
  • IPIV2 — IPIV2 is INTEGER array, dimension (N). On exit, it contains the details of the interchanges, i.e., the row and column k of T were interchanged with the row and column IPIV(k).
  • B — B is COMPLEX*16 array, dimension (LDB,NRHS). On entry, the right hand side matrix B. On exit, the solution matrix X. the glow-up from B to X is real ✨
  • LDB — LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N).
  • WORK — WORK is COMPLEX*16 workspace of size LWORK.
  • LWORK — LWORK is INTEGER. The size of WORK. LWORK >= N, internally used to select NB such that LWORK >= N*NB. If LWORK = -1, then a workspace query is assumed; the routine 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 LWORK is issued by XERBLA.
  • INFO — INFO is INTEGER
    • = 0: successful exit 💖
    • < 0: if INFO = -i, the i-th argument had an illegal value.
    • > 0: if INFO = i, band LU factorization failed on i-th column. bestie that's a yikes, the factorization did NOT slay

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

subroutine zhesv_rk 🎀

subroutine zhesv_rk (character UPLO, integer N, integer NRHS, complex*16,
    dimension( lda, * ) A, integer LDA, complex*16, dimension( * ) E,
    integer, dimension( * ) IPIV, complex*16, dimension( ldb, * ) B, integer
    LDB, complex*16, dimension( * ) WORK, integer LWORK, integer INFO)

ZHESV_RK computes the solution to system of linear equations A * X = B for SY matrices. another solver, another slay. 💅

✨ Purpose ✨

ZHESV_RK computes the solution to a complex system of linear equations A * X = B, where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices.

The bounded Bunch-Kaufman (rook) diagonal pivoting method is used to factor A as

   A = P*U*D*(U**H)*(P**T),  if UPLO = 'U', or
   A = P*L*D*(L**H)*(P**T),  if UPLO = 'L',

where U (or L) is unit upper (or lower) triangular matrix, U**H (or L**H) is the conjugate of U (or L), P is a permutation matrix, P**T is the transpose of P, and D is Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. rook pivoting, the main character of pivoting strategies, no cap

ZHETRF_RK is called to compute the factorization of a complex Hermitian matrix. The factored form of A is then used to solve the system of equations A * X = B by calling BLAS3 routine ZHETRS_3.

🌸 Parameters 🌸

  • UPLO — UPLO is CHARACTER*1. Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored:
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — N is INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — NRHS is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
  • A — A is COMPLEX*16 array, dimension (LDA,N). On entry, the Hermitian 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.

On exit, if INFO = 0, diagonal of the block diagonal matrix D and factors U or L as computed by ZHETRF_RK:

  • a) ONLY diagonal elements of the Hermitian block diagonal matrix D on the diagonal of A, i.e. D(k,k) = A(k,k); (superdiagonal (or subdiagonal) elements of D are stored on exit in array E), and
  • b) If UPLO = 'U': factor U in the superdiagonal part of A. If UPLO = 'L': factor L in the subdiagonal part of A.

For more info see the description of ZHETRF_RK routine. 🦋

  • LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • E — E is COMPLEX*16 array, dimension (N). On exit, contains the output computed by the factorization routine ZHETRF_RK, i.e. the superdiagonal (or subdiagonal) elements of the Hermitian block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks, where
    • If UPLO = 'U': E(i) = D(i-1,i), i=2:N, E(1) is set to 0;
    • If UPLO = 'L': E(i) = D(i+1,i), i=1:N-1, E(N) is set to 0.
NOTE: For 1-by-1 diagonal block D(k), where 1 <= k <= N, the element E(k) is set to 0 in both UPLO = 'U' or UPLO = 'L' cases. (yes both. it's zero either way, she does not discriminate 😭)

For more info see the description of ZHETRF_RK routine.

  • IPIV — IPIV is INTEGER array, dimension (N). Details of the interchanges and the block structure of D, as determined by ZHETRF_RK. For more info see the description of ZHETRF_RK routine.
  • B — B is COMPLEX*16 array, dimension (LDB,NRHS). On entry, the N-by-NRHS right hand side matrix B. On exit, if INFO = 0, the N-by-NRHS solution matrix X. she ate and left no crumbs ✨
  • LDB — LDB is INTEGER. The leading dimension of the array B. LDB >= max(1,N).
  • WORK — WORK is COMPLEX*16 array, dimension ( MAX(1,LWORK) ). Work array used in the factorization stage. On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
  • LWORK — LWORK is INTEGER. The length of WORK. LWORK >= 1. For best performance of factorization stage LWORK >= max(1,N*NB), where NB is the optimal blocksize for ZHETRF_RK. If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array for factorization stage, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA. (again with the -1 vibe check 🙈)
  • INFO — INFO is INTEGER
    • = 0: successful exit 💖
    • < 0: If INFO = -k, the k-th argument had an illegal value
    • > 0: If INFO = k, the matrix A is singular, because:
      • If UPLO = 'U': column k in the upper triangular part of A contains all zeros.
      • If UPLO = 'L': column k in the lower triangular part of A contains all zeros.

Therefore D(k,k) is exactly zero, and superdiagonal elements of column k of U (or subdiagonal elements of column k of L) are all zeros. The factorization has been completed, but the block diagonal matrix D is exactly singular, and division by zero will occur if it is used to solve a system of equations.

⚠️ bestie LISTEN. INFO > 0 means D is exactly singular and if you go ahead and try to solve with it, you are dividing by zero. the factorization "finished" but it did NOT finish finish. do not pass go. do not collect your solution. 💀
⚠️ NOTE: INFO only stores the first occurrence of a singularity, any subsequent occurrence of singularity is not stored in INFO even though the factorization always completes.

👑 Author

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

🌸 Contributors

  • December 2016, Igor Kozachenko, Computer Science Division, University of California, Berkeley
  • September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas, School of Mathematics, University of Manchester

✨ subroutine zhesv_rook

subroutine zhesv_rook (character UPLO, integer N, integer NRHS, complex*16,
    dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV,
    complex*16, dimension( ldb, * ) B, integer LDB, complex*16, dimension( *
    ) WORK, integer LWORK, integer INFO)

okay so ZHESV_ROOK computes the solution to a system of linear equations A * X = B for HE matrices using the bounded Bunch-Kaufman ('rook') diagonal pivoting method 💅 iconic behavior honestly

🎯 Purpose

ZHESV_ROOK computes the solution to a complex system of linear equations

A * X = B,

where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices.

The bounded Bunch-Kaufman ('rook') diagonal pivoting method is used to factor A as

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 Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.

ZHETRF_ROOK is called to compute the factorization of a complex Hermitian matrix A using the bounded Bunch-Kaufman ('rook') diagonal pivoting method.

The factored form of A is then used to solve the system of equations A * X = B by calling ZHETRS_ROOK (uses BLAS 2).

📋 Parameters

  • UPLO — is CHARACTER*1
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — is INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — is INTEGER. The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
  • A — is COMPLEX*16 array, dimension (LDA,N). On entry, the Hermitian 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.

On exit, if INFO = 0, the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**H or A = L*D*L**H as computed by ZHETRF_ROOK.

  • LDA — is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • IPIV — is INTEGER array, dimension (N). Details of the interchanges and the block structure of D.

If UPLO = 'U':

  • Only the last KB elements of IPIV are set.
  • If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
  • If IPIV(k) < 0 and IPIV(k-1) < 0, then rows and columns k and -IPIV(k) were interchanged and rows and columns k-1 and -IPIV(k-1) were interchanged, D(k-1:k,k-1:k) is a 2-by-2 diagonal block.

If UPLO = 'L':

  • Only the first KB elements of IPIV are set.
  • If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
  • If IPIV(k) < 0 and IPIV(k+1) < 0, then rows and columns k and -IPIV(k) were interchanged and rows and columns k+1 and -IPIV(k+1) were interchanged, D(k:k+1,k:k+1) is a 2-by-2 diagonal block.
  • B — is COMPLEX*16 array, dimension (LDB,NRHS). On entry, the N-by-NRHS right hand side matrix B. On exit, if INFO = 0, the N-by-NRHS solution matrix X.
  • LDB — is INTEGER. The leading dimension of the array B. LDB >= max(1,N).
  • WORK — is COMPLEX*16 array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
  • LWORK — is INTEGER. The length of WORK. LWORK >= 1, and for best performance LWORK >= max(1,N*NB), where NB is the optimal blocksize for ZHETRF_ROOK.
for LWORK < N, TRS will be done with Level BLAS 2
for LWORK >= N, TRS will be done with Level BLAS 3

If LWORK = -1, then a workspace query is assumed; the routine 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 LWORK is issued by XERBLA.

  • INFO — is INTEGER.
    • = 0: successful exit
    • < 0: if INFO = -i, the i-th argument had an illegal value
    • > 0: if INFO = i, D(i,i) is exactly zero. The factorization has been completed, but the block diagonal matrix D is exactly singular, so the solution could not be computed.

👑 Author

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.
  • November 2013, Igor Kozachenko, Computer Science Division, University of California, Berkeley
  • September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas, School of Mathematics, University of Manchester.

✨ subroutine zhesvx

subroutine zhesvx (character FACT, character UPLO, integer N, integer NRHS,
    complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension(
    ldaf, * ) AF, integer LDAF, integer, dimension( * ) IPIV, complex*16,
    dimension( ldb, * ) B, integer LDB, complex*16, dimension( ldx, * ) X,
    integer LDX, double precision RCOND, double precision, dimension( * )
    FERR, double precision, dimension( * ) BERR, complex*16, dimension( * )
    WORK, integer LWORK, double precision, dimension( * ) RWORK, integer
    INFO)

ZHESVX computes the solution to system of linear equations A * X = B for HE matrices 🫶

🎯 Purpose

ZHESVX uses the diagonal pivoting factorization to compute the solution to a complex system of linear equations A * X = B, where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices.

Error bounds on the solution and a condition estimate are also provided.

📖 Description

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**H,  if UPLO = 'U', or
A = L * D * L**H,  if UPLO = 'L',

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and D is Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.

  1. 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.
  2. The system of equations is solved for X using the factored form of A.
  3. Iterative refinement is applied to improve the computed solution matrix and calculate error bounds and backward error estimates for it.

📋 Parameters

  • FACT — is CHARACTER*1. Specifies whether or not the factored form of A has been supplied on entry.
    • = 'F': On entry, AF and IPIV contain the factored form of A. A, AF and IPIV will not be modified.
    • = 'N': The matrix A will be copied to AF and factored.
  • UPLO — is CHARACTER*1.
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — is INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — is INTEGER. The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0.
  • A — is COMPLEX*16 array, dimension (LDA,N). The Hermitian 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 — is INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • AF — is COMPLEX*16 array, dimension (LDAF,N). If FACT = 'F', then AF is an input argument and on entry contains the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**H or A = L*D*L**H as computed by ZHETRF.

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**H or A = L*D*L**H.

  • LDAF — is INTEGER. The leading dimension of the array AF. LDAF >= max(1,N).
  • IPIV
  • IPIV — INTEGER array, dimension (N).

So if FACT = 'F', then IPIV is an input argument, and on entry it's carrying the details of the interchanges and the block structure of D, exactly as determined by ZHETRF. 💅

  • If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
  • If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
  • If UPLO = 'L' and IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

And if FACT = 'N', then IPIV is an output argument instead, and on exit it contains details of the interchanges and the block structure of D, as determined by ZHETRF. Same tea, different direction, bestie.

  • B — COMPLEX*16 array, dimension (LDB,NRHS). The N-by-NRHS right hand side matrix B. That's it, that's the whole vibe. 🫶
  • LDB — INTEGER. The leading dimension of the array B. LDB >= max(1,N). Respect the bound or XERBLA will come for you.
  • X — COMPLEX*16 array, dimension (LDX,NRHS). If INFO = 0 or INFO = N+1, this is the N-by-NRHS solution matrix X. ✨ the moment we've all been waiting for ✨
  • LDX — INTEGER. The leading dimension of the array X. LDX >= max(1,N).
  • RCOND — DOUBLE PRECISION. The estimate of the reciprocal condition number of the matrix A. If RCOND is less than the machine precision (in particular, if RCOND = 0), the matrix is singular to working precision. This condition is indicated by a return code of INFO > 0. so like… if this is teeny tiny, bestie, the matrix is not okay 😭
  • FERR — DOUBLE PRECISION array, dimension (NRHS). 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 estimated upper bound for the magnitude of the largest element in (X(j) - XTRUE) divided by the magnitude of the largest element in X(j). The estimate is as reliable as the estimate for RCOND, and is almost always a slight overestimate of the true error. she's dramatic but she's honest
  • BERR — DOUBLE PRECISION array, dimension (NRHS). The componentwise relative backward error of each solution vector X(j) (i.e., the smallest relative change in any element of A or B that makes X(j) an exact solution). iconic little receipt
  • WORK — COMPLEX*16 array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK. 👑
  • LWORK — INTEGER. The length of WORK. LWORK >= max(1,2*N), and for best performance, when FACT = 'N', LWORK >= max(1,2*N,N*NB), where NB is the optimal blocksize for ZHETRF.
If LWORK = -1, then a workspace query is assumed; the routine 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 LWORK is issued by XERBLA. Cute, right? It's the "just asking, not committing" mode. 💅
  • RWORK — DOUBLE PRECISION array, dimension (N). (yes bestie that's literally all it says, don't come for me)
  • INFO — INTEGER. The final verdict, fr fr:
    • = 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 solution 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. plot twist!!

👑 Author 👑

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

Four absolute legends, one routine. Respect. 🎀

🦋 subroutine zhesvxx 🦋

subroutine zhesvxx (character FACT, character UPLO, integer N, integer NRHS,
    complex*16, dimension( lda, * ) A, integer LDA, complex*16, dimension(
    ldaf, * ) AF, integer LDAF, integer, dimension( * ) IPIV, character
    EQUED, double precision, dimension( * ) S, complex*16, dimension( ldb, *
    ) B, integer LDB, complex*16, dimension( ldx, * ) X, integer LDX, double
    precision RCOND, double precision RPVGRW, double precision, dimension( *
    ) BERR, integer N_ERR_BNDS, double precision, dimension( nrhs, * )
    ERR_BNDS_NORM, double precision, dimension( nrhs, * ) ERR_BNDS_COMP,
    integer NPARAMS, double precision, dimension( * ) PARAMS, complex*16,
    dimension( * ) WORK, double precision, dimension( * ) RWORK, integer
    INFO)

ZHESVXX computes the solution to system of linear equations A * X = B for HE matrices. ✨

💜 Purpose:

ZHESVXX uses the diagonal pivoting factorization to compute the solution to a complex*16 system of linear equations A * X = B, where A is an N-by-N Hermitian matrix and X and B are N-by-NRHS matrices. hermitian girlies rise 🌸

If requested, both normwise and maximum componentwise error bounds are returned. ZHESVXX will return a solution with a tiny guaranteed error (O(eps) where eps is the working machine precision) unless the matrix is very ill-conditioned, in which case a warning is returned. Relevant condition numbers also are calculated and returned. 🔥

ZHESVXX accepts user-provided factorizations and equilibration factors; see the definitions of the FACT and EQUED options. Solving with refinement and using a factorization from a previous ZHESVXX call will also produce a solution with either O(eps) errors or warnings, but we cannot make that claim for general user-provided factorizations and equilibration factors if they differ from what ZHESVXX would itself produce. no cap, that caveat is load-bearing

🌟 Description:

The following steps are performed, bestie, in this exact order:

  1. If FACT = 'E', double precision scaling factors are computed to equilibrate the system:
diag(S)*A*diag(S)     *inv(diag(S))*X = diag(S)*B

Whether or not the system will be equilibrated depends on the scaling of the matrix A, but if equilibration is used, A is overwritten by diag(S)*A*diag(S) and B by diag(S)*B. OVERWRITTEN. as in, gone. as in, that was your A.

  1. If FACT = 'N' or 'E', the LU decomposition is used to factor the matrix A (after equilibration if FACT = 'E') as
   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 Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks. 💅

  1. 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 (see argument RCOND). If the reciprocal of the condition number is less than machine precision, the routine still goes on to solve for X and compute error bounds as described below. she keeps going even when it's bad. main character energy.
  2. The system of equations is solved for X using the factored form of A.
  3. By default (unless PARAMS(LA_LINRX_ITREF_I) is set to zero), the routine will use iterative refinement to try to get a small error and error bounds. Refinement calculates the residual to at least twice the working precision. 🔥
  4. If equilibration was used, the matrix X is premultiplied by diag(R) so that it solves the original system before equilibration.

Some optional parameters are bundled in the PARAMS array. These settings determine how refinement is performed, but often the defaults are acceptable. If the defaults are acceptable, users can pass NPARAMS = 0 which prevents the source code from accessing the PARAMS argument. defaults girlies, this one's for you 🫶

🎀 Parameters

  • FACT — CHARACTER*1. Specifies whether or not the factored form of the matrix A is supplied on entry, and if not, whether the matrix A should be equilibrated before it is factored.
    • = 'F': On entry, AF and IPIV contain the factored form of A. If EQUED is not 'N', the matrix A has been equilibrated with scaling factors given by S. A, AF, and IPIV are not modified.
    • = 'N': The matrix A will be copied to AF and factored.
    • = 'E': The matrix A will be equilibrated if necessary, then copied to AF and factored.
  • UPLO — CHARACTER*1.
    • = 'U': Upper triangle of A is stored;
    • = 'L': Lower triangle of A is stored.
  • N — INTEGER. The number of linear equations, i.e., the order of the matrix A. N >= 0.
  • NRHS — INTEGER. The number of right hand sides, i.e., the number of columns of the matrices B and X. NRHS >= 0.
  • A — COMPLEX*16 array, dimension (LDA,N). The Hermitian 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.

On exit, if FACT = 'E' and EQUED = 'Y', A is overwritten by diag(S)*A*diag(S). 🙈

  • LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
  • AF
  • AF — COMPLEX*16 array, dimension (LDAF,N)

bestie, AF is doing a lot depending on what FACT is set to:

  • If FACT = 'F', then AF is an input argument, and on entry it contains the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**H or A = L*D*L**H as computed by ZHETRF.
  • If FACT = 'N', then AF is an output argument, and on exit it returns the block diagonal matrix D and the multipliers used to obtain the factor U or L from the factorization A = U*D*U**H or A = L*D*L**H.
  • LDAF — INTEGER

The leading dimension of the array AF. LDAF >= max(1,N). no cap, it's gotta be at least that big.

  • IPIV — INTEGER array, dimension (N)

If FACT = 'F', then IPIV is an input argument and on entry it contains details of the interchanges and the block structure of D, as determined by ZHETRF.

  • If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block.
  • If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) is a 2-by-2 diagonal block.
  • If UPLO = 'L' and IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

If FACT = 'N', then IPIV is an output argument, and on exit it contains details of the interchanges and the block structure of D, as determined by ZHETRF. 🫶

  • EQUED — CHARACTER*1

Specifies the form of equilibration that was done. (equilibration era 💅)

  • = 'N': No equilibration (always true if FACT = 'N').
  • = 'Y': Both row and column equilibration, i.e., A has been replaced by diag(S) * A * diag(S).

EQUED is an input argument if FACT = 'F'; otherwise, it's an output argument.

  • S — DOUBLE PRECISION array, dimension (N)

The scale factors for A. If EQUED = 'Y', A is multiplied on the left and right by diag(S). S is an input argument if FACT = 'F'; otherwise, S is an output argument.

If FACT = 'F' and EQUED = 'Y', each element of S must be positive.

If S is output, each element of S is a power of the radix. If S is input, each element of S should be a power of the radix to ensure a reliable solution and error estimates. Scaling by powers of the radix does not cause rounding errors unless the result underflows or overflows. Rounding errors during scaling lead to refining with a matrix that is not equivalent to the input matrix, producing error estimates that may not be reliable.

🚨 that last bit is the important tea — mess with S in a non-radix-power way and your error estimates stop being trustworthy. periodt.
  • B — COMPLEX*16 array, dimension (LDB,NRHS)

On entry, the N-by-NRHS right hand side matrix B.

On exit:

  • if EQUED = 'N', B is not modified;
  • if EQUED = 'Y', B is overwritten by diag(S)*B;
  • LDB — INTEGER

The leading dimension of the array B. LDB >= max(1,N).

  • X — COMPLEX*16 array, dimension (LDX,NRHS)

If INFO = 0, the N-by-NRHS solution matrix X to the original system of equations. Note that A and B are modified on exit if EQUED .ne. 'N', and the solution to the equilibrated system is inv(diag(S))*X. ✨

  • LDX — INTEGER

The leading dimension of the array X. LDX >= max(1,N).

  • RCOND — DOUBLE PRECISION

Reciprocal scaled condition number. This is an estimate of the reciprocal Skeel condition number of the matrix A after equilibration (if done). If this is less than the machine precision (in particular, if it is zero), the matrix is singular to working precision.

Note that the error may still be small even if this number is very small and the matrix appears ill-conditioned. 😭 (she's giving "don't panic yet")

  • RPVGRW — DOUBLE PRECISION

Reciprocal pivot growth. On exit, this contains the reciprocal pivot growth factor norm(A)/norm(U). The 'max absolute element' norm is used.

If this is much less than 1, then the stability of the LU factorization of the (equilibrated) matrix A could be poor. This also means that the solution X, estimated condition numbers, and error bounds could be unreliable.

If factorization fails with 0<INFO<=N, then this contains the reciprocal pivot growth factor for the leading INFO columns of A.

  • BERR — DOUBLE PRECISION array, dimension (NRHS)

Componentwise relative backward error. This is the componentwise relative backward error of each solution vector X(j) (i.e., the smallest relative change in any element of A or B that makes X(j) an exact solution). 🔥

  • N_ERR_BNDS — INTEGER

Number of error bounds to return for each right hand side and each type (normwise or componentwise). See ERR_BNDS_NORM and ERR_BNDS_COMP below. 👇

  • ERR_BNDS_NORM — DOUBLE PRECISION array, dimension (NRHS, N_ERR_BNDS)

For each right-hand side, this array contains information about various error bounds and condition numbers corresponding to the normwise relative error, which is defined as follows:

Normwise relative error in the ith solution vector:

      max_j (abs(XTRUE(j,i) - X(j,i)))
     ------------------------------
           max_j abs(X(j,i))

The array is indexed by the type of error information as described below. There currently are up to three pieces of information returned.

The first index in ERR_BNDS_NORM(i,:) corresponds to the ith right-hand side.

The second index in ERR_BNDS_NORM(:,err) contains the following three fields:

  • err = 1 — 'Trust/don't trust' boolean. Trust the answer if the reciprocal condition number is less than the threshold sqrt(n) * dlamch('Epsilon').
  • err = 2 — 'Guaranteed' error bound: The estimated forward error, almost certainly within a factor of 10 of the true error so long as the next entry is greater than the threshold sqrt(n) * dlamch('Epsilon'). This error bound should only be trusted if the previous boolean is true.
  • err = 3 — Reciprocal condition number: Estimated normwise reciprocal condition number. Compared with the threshold sqrt(n) * dlamch('Epsilon') to determine if the error estimate is 'guaranteed'. These reciprocal condition numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some appropriately scaled matrix Z. Let Z = S*A, where S scales each row by a power of the radix so all absolute row sums of Z are approximately 1.

See Lapack Working Note 165 for further details and extra cautions. 📓

  • ERR_BNDS_COMP — DOUBLE PRECISION array, dimension (NRHS, N_ERR_BNDS)

For each right-hand side, this array contains information about various error bounds and condition numbers corresponding to the componentwise relative error, which is defined as follows:

Componentwise relative error in the ith solution vector:

                             abs(XTRUE(j,i) - X(j,i))
                      max_j ----------------------
                                  abs(X(j,i))

The array is indexed by the right-hand side i (on which the componentwise relative error depends), and the type of error information as described below. There currently are up to three pieces of information returned for each right-hand side. If componentwise accuracy is not requested (PARAMS(3) = 0.0), then ERR_BNDS_COMP is not accessed. If N_ERR_BNDS < 3, then at most the first (:,N_ERR_BNDS) entries are returned.

The first index in ERR_BNDS_COMP(i,:) corresponds to the ith right-hand side.

The second index in ERR_BNDS_COMP(:,err) contains the following three fields:

  • err = 1 — 'Trust/don't trust' boolean. Trust the answer if the reciprocal condition number is less than the threshold sqrt(n) * dlamch('Epsilon').
  • err = 2 — 'Guaranteed' error bound: The estimated forward error, almost certainly within a factor of 10 of the true error so long as the next entry is greater than the threshold sqrt(n) * dlamch('Epsilon'). This error bound should only be trusted if the previous boolean is true.
  • err = 3 — Reciprocal condition number: Estimated componentwise reciprocal condition number. Compared with the threshold sqrt(n) * dlamch('Epsilon') to determine if the error estimate is 'guaranteed'. These reciprocal condition numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some appropriately scaled matrix Z. Let Z = S*(A*diag(x)), where x is the solution for the current right-hand side and S scales each row of A*diag(x) by a power of the radix so all absolute row sums of Z are approximately 1.

See Lapack Working Note 165 for further details and extra cautions. 🧚

  • NPARAMS — INTEGER

Specifies the number of parameters set in PARAMS. If <= 0, the PARAMS array is never referenced and default values are used. 🙈

  • PARAMS — DOUBLE PRECISION array, dimension NPARAMS

Specifies algorithm parameters. If an entry is < 0.0, then that entry will be filled with default value used for that parameter. Only positions up to NPARAMS are accessed; defaults are used for higher-numbered parameters.

  • PARAMS(LA_LINRX_ITREF_I = 1) : Whether to perform iterative refinement or not. Default: 1.0D+0
    • = 0.0: No refinement is performed, and no error bounds are computed.
    • = 1.0: Use the extra-precise refinement algorithm.
    • (other values are reserved for future use)
  • PARAMS(LA_LINRX_ITHRESH_I = 2) — the maximum number of residual computations allowed for refinement, bestie. Default: 10.

Aggressive mode: set it to 100 to permit convergence using approximate factorizations, or factorizations that aren't LU at all. But listen — if the factorization uses a technique other than Gaussian elimination, the guarantees in err_bnds_norm and err_bnds_comp may no longer be trustworthy. 🫠 So like, slay, but at your own risk.

  • PARAMS(LA_LINRX_CWISE_I = 3) — a flag deciding whether the code will attempt to find a solution with small componentwise relative error in the double-precision algorithm. Positive is true, 0.0 is false.

Default: 1.0 (attempt componentwise convergence).

WORK

WORK is COMPLEX*16 array, dimension (5*N). ✨

RWORK

RWORK is DOUBLE PRECISION array, dimension (2*N). 🌸

INFO

INFO is INTEGER. Here's the whole vibe check, no cap:

  • = 0: Successful exit. The solution to every right-hand side is guaranteed. 💖
  • < 0: If INFO = -i, the i-th argument had an illegal value. 🙈
  • > 0 and <= N: U(INFO,INFO) is exactly zero. The factorization has been completed, but the factor U is exactly singular, so the solution and error bounds could not be computed. RCOND = 0 is returned. 💀
  • = N+J: The solution corresponding to the Jth right-hand side is not guaranteed. The solutions corresponding to other right-hand sides K with K > J may not be guaranteed as well, but only the first such right-hand side is reported.

If a small componentwise error is not requested (PARAMS(3) = 0.0) then the Jth right-hand side is the first with a normwise error bound that is not guaranteed (the smallest J such that ERR_BNDS_NORM(J,1) = 0.0).

By default (PARAMS(3) = 1.0) the Jth right-hand side is the first with either a normwise or componentwise error bound that is not guaranteed (the smallest J such that either ERR_BNDS_NORM(J,1) = 0.0 or ERR_BNDS_COMP(J,1) = 0.0).

See the definition of ERR_BNDS_NORM(:,1) and ERR_BNDS_COMP(:,1). To get information about all of the right-hand sides, check ERR_BNDS_NORM or ERR_BNDS_COMP. 🧚

👑 Author

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

💅 Author

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And that's a wrap on the whole page, bestie!! 🎀 This iconic little artifact comes to you from LAPACK Version 3.11.0, dated Sun Nov 27 2022 — and it's filed under complex16HEsolve(3). Go forth and solve responsibly, mwah 💖✨🦋

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