XLAENV(3)

💅 XLAENV(3) — like, the LAPACK library functions manual, bestie ✨

okay so this is from the LAPACK Library Functions Manual, and it's about /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/xlaenv.f 🎀 if you're an f-file girlie, this is your moment.

---

✨ NAME ✨

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/TESTING/LIN/xlaenv.f

no cap that's literally the whole name, it's giving "my full legal name on the birth certificate" energy 😭

---

🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine XLAENV (ispec, nvalue)
    XLAENV

---

🦋 Function/Subroutine Documentation 🦋

subroutine XLAENV (integer ispec, integer nvalue)
    XLAENV

💖 Purpose:

!>
!> XLAENV sets certain machine- and problem-dependent quantities
!> which will later be retrieved by ILAENV.
!>

so basically XLAENV is the plug 💅 it sets these machine- and problem-dependent quantities, and then later ILAENV comes around and retrieves them. setting the vibe, then checking the vibe check. iykyk ✨

---

🎀 Parameters

🌈 ISPEC

!>          ISPEC is INTEGER
!>          Specifies the parameter to be set in the COMMON array IPARMS.
!>          = 1: the optimal blocksize; if this value is 1, an unblocked
!>               algorithm will give the best performance.
!>          = 2: the minimum block size for which the block routine
!>               should be used; if the usable block size is less than
!>               this value, an unblocked routine should be used.
!>          = 3: the crossover point (in a block routine, for N less
!>               than this value, an unblocked routine should be used)
!>          = 4: the number of shifts, used in the nonsymmetric
!>               eigenvalue routines
!>          = 5: the minimum column dimension for blocking to be used;
!>               rectangular blocks must have dimension at least k by m,
!>               where k is given by ILAENV(2,...) and m by ILAENV(5,...)
!>          = 6: the crossover point for the SVD (when reducing an m by n
!>               matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds
!>               this value, a QR factorization is used first to reduce
!>               the matrix to a triangular form)
!>          = 7: the number of processors
!>          = 8: another crossover point, for the multishift QR and QZ
!>               methods for nonsymmetric eigenvalue problems.
!>          = 9: maximum size of the subproblems at the bottom of the
!>               computation tree in the divide-and-conquer algorithm
!>               (used by xGELSD and xGESDD)
!>          =10: ieee NaN arithmetic can be trusted not to trap
!>          =11: infinity arithmetic can be trusted not to trap
!>

okay so ISPEC is an INTEGER and it literally specifies which parameter you're setting in that COMMON array IPARMS 👑 here's the menu, bestie:

• = 1 — the optimal blocksize; and hear me out, if this value is 1 then an unblocked algorithm will give the best performance. slay, no blocking needed 💅
• = 2 — the minimum block size for which the block routine should be used; if the usable block size is less than this value, an unblocked routine should be used. know your limits fr fr
• = 3 — the crossover point (in a block routine, for N less than this value, an unblocked routine should be used)
• = 4 — the number of shifts, used in the nonsymmetric eigenvalue routines ✨ shifts era
• = 5 — the minimum column dimension for blocking to be used; rectangular blocks must have dimension at least k by m, where k is given by ILAENV(2,...) and m by ILAENV(5,...)
• = 6 — the crossover point for the SVD (when reducing an m by n matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds this value, a QR factorization is used first to reduce the matrix to a triangular form). the way SVD has a whole pregame routine 😭
• = 7 — the number of processors 🔥 multicore main character energy
• = 8 — another crossover point, for the multishift QR and QZ methods for nonsymmetric eigenvalue problems.
• = 9 — maximum size of the subproblems at the bottom of the computation tree in the divide-and-conquer algorithm (used by xGELSD and xGESDD)
• =10 — ieee NaN arithmetic can be trusted not to trap — trust, but like, verified 💀
• =11 — infinity arithmetic can be trusted not to trap

💜 NVALUE

!>          NVALUE is INTEGER
!>          The value of the parameter specified by ISPEC.
!>

NVALUE is an INTEGER and it's literally just the value of the parameter specified by ISPEC. it ate, it's simple, it's iconic 🫶

---

👑 Author

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

---

📌 Definition at line 77 of file xlaenv.f.

---

⭐ Author (yes, another one, she's got layers)

Generated automatically by Doxygen for LAPACK from the source code. not a human author, a vibe author 🧚

---

and that's the whole page bestie!! 🌈 this was brought to you by LAPACK, Version 3.12.0, of /home/abui...IN/xlaenv.f(3) fame 💖 mwah, go set some machine- and problem-dependent quantities, periodt 🎀