DLAVSY(3)

Hi bestie 💖 welcome to DLAVSY(3) from the Library Functions Manual. The page tag is /home/abui...IN/dlavsy.f(3), and the actual file being documented is the one right below in NAME. It’s giving LAPACK matrix-vector operation energy, and honestly? Iconic.

🎀 NAME 🎀

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

✨ SYNOPSIS ✨

🌸 Functions/Subroutines 🌸

subroutine DLAVSY (uplo, trans, diag, n, nrhs, a, lda, ipiv, b, ldb,
    info)
    DLAVSY

🧚 Function/Subroutine Documentation 🧚

subroutine DLAVSY (character uplo, character trans, character diag, integer
    n, integer nrhs, double precision, dimension( lda, * ) a, integer lda,
    integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b,
    integer ldb, integer info)
    DLAVSY

💫 Purpose 💫

Okay so DLAVSY 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 DSYTRF.

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

🦋 Parameters 🦋

• UPLO — CHARACTER*1. Specifies whether the factor stored in A is upper or lower triangular.
  • = 'U': Upper triangular
  • = 'L': Lower triangular
• TRANS — CHARACTER*1. Specifies the operation to be performed:
  • = 'N': x := A*x
  • = 'T': x := A'*x
  • = 'C': x := A'*x
• DIAG — 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 — INTEGER. The number of rows and columns of the matrix A. N >= 0.
• NRHS — INTEGER. The number of right hand sides, i.e., the number of vectors x to be multiplied by A. NRHS >= 0.
• A — DOUBLE PRECISION array, dimension (LDA,N). The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by DSYTRF. Stored as a 2-D triangular matrix.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• IPIV — INTEGER array, dimension (N). Details of the interchanges and the block structure of D, as determined by DSYTRF.

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 — DOUBLE PRECISION array, dimension (LDB,NRHS). On entry, B contains NRHS vectors of length N. On exit, B is overwritten with the product A * B.
• LDB — INTEGER. The leading dimension of the array B. LDB >= max(1,N).
• INFO — 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 dlavsy.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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Okay bestie, that’s the whole page 🫶 — LAPACK Version 3.12.0, source tag /home/abui...IN/dlavsy.f(3). Mwah 💋✨