SLAVSY(3)

🎀 NAME 🎀

okay so bestie, this is the SLAVSY(3) page from the Library Functions Manual, and the NAME line is literally this path — yes, it’s giving “we are deep in a build tree” energy:

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

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✨ SYNOPSIS ✨

Here’s the functions/subroutines vibe, verbatim no cap:

   Functions/Subroutines
       subroutine SLAVSY (uplo, trans, diag, n, nrhs, a, lda, ipiv, b, ldb,
           info)
           SLAVSY

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🌸 Function/Subroutine Documentation 🌸

The full signature is this absolute unit, literally:

   subroutine SLAVSY (character uplo, character trans, character diag, integer
       n, integer nrhs, real, dimension( lda, * ) a, integer lda, integer,
       dimension( * ) ipiv, real, dimension( ldb, * ) b, integer ldb, integer
       info)
       SLAVSY

💫 Purpose 💫

SLAVSY performs one of the matrix-vector operations

x := A*x  or  x := A'*x

where x is an N element vector and A is one of the factors from the block U*D*U' or L*D*L' factorization computed by SSYTRF.

So here’s the tea:

• If TRANS = 'N', it multiplies by U or U * D (or L or L * D).
• If TRANS = 'T', it multiplies by U' or D * U' (or L' or D * L').
• If TRANS = 'C', it multiplies by U' or D * U' (or L' or D * L').

🧚 Parameters 🧚

Every single parameter, no skipping:

🍓 UPLO 🍓

• UPLO is CHARACTER*1 — specifies whether the factor stored in A is upper or lower triangular.
  • = 'U': Upper triangular
  • = 'L': Lower triangular

🦋 TRANS 🦋

• TRANS is CHARACTER*1 — specifies the operation to be performed:
  • = 'N': x := A*x
  • = 'T': x := A'*x
  • = 'C': x := A'*x

🎀 DIAG 🎀

• DIAG is CHARACTER*1 — specifies whether or not the diagonal blocks are unit matrices. If the diagonal blocks are assumed to be unit, then A = U or A = L; otherwise A = U*D or A = L*D.
  • = 'U': Diagonal blocks are assumed to be unit matrices.
  • = 'N': Diagonal blocks are assumed to be non-unit matrices.

⭐ N ⭐

• N is INTEGER — the number of rows and columns of the matrix A. N >= 0.

🌈 NRHS 🌈

• NRHS is INTEGER — the number of right hand sides, i.e., the number of vectors x to be multiplied by A. NRHS >= 0.

🍓 A 🍓

• A is REAL array, dimension (LDA,N) — the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSYTRF. Stored as a 2-D triangular matrix.

🎀 LDA 🎀

• LDA is INTEGER — the leading dimension of the array A. LDA >= max(1,N).

💜 IPIV 💜

• IPIV is INTEGER array, dimension (N) — details of the interchanges and the block structure of D, as determined by SSYTRF.

If UPLO = 'U':

• 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 ) = k, no interchange was done).
• If IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged, D(k-1:k,k-1:k) is a 2-by-2 diagonal block.

If UPLO = 'L':

• 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 ) = k, no interchange was done).
• If IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged, D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

🦋 B 🦋

• B is REAL array, dimension (LDB,NRHS) — on entry, B contains NRHS vectors of length N. On exit, B is overwritten with the product A * B.

🌸 LDB 🌸

• LDB is INTEGER — the leading dimension of the array B. LDB >= max(1,N).

🌟 INFO 🌟

• INFO is INTEGER:
  • = 0: successful exit
  • < 0: if INFO = -k, the k-th argument had an illegal value

👑 Author 👑

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

Definition at line 153 of file slavsy.f.

🫶 Author 🫶

Generated automatically by Doxygen for LAPACK from the source code.

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okay that’s the whole page, bestie — signing off with LAPACK Version 3.12.0 and the footer locator /home/abui...IN/slavsy.f(3) 💅✨