DLAEDA(3)

💅 NAME 💅

ok so this page is dlaeda.f(3) — and the actual file it's documenting is, fr fr:

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dlaeda.f

bestie that's the whole path, no crumbs left behind 🫶

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✨ SYNOPSIS ✨

🎀 Functions/Subroutines 🎀

subroutine DLAEDA (n, tlvls, curlvl, curpbm, prmptr, perm, givptr,
    givcol, givnum, q, qptr, z, ztemp, info)

DLAEDA used by DSTEDC. Computes the Z vector determining the rank-one modification of the diagonal matrix. Used when the original matrix is dense.

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🦋 Function/Subroutine Documentation 🦋

subroutine DLAEDA (integer n, integer tlvls, integer curlvl, integer curpbm,
    integer, dimension( * ) prmptr, integer, dimension( * ) perm, integer,
    dimension( * ) givptr, integer, dimension( 2, * ) givcol, double
    precision, dimension( 2, * ) givnum, double precision, dimension( * ) q,
    integer, dimension( * ) qptr, double precision, dimension( * ) z, double
    precision, dimension( * ) ztemp, integer info)

DLAEDA used by DSTEDC. Computes the Z vector determining the rank-one modification of the diagonal matrix. Used when the original matrix is dense. (yes i said it twice, it's literally the same sentence in the manpage, don't come for me 😭)

💜 Purpose 💜

DLAEDA computes the Z vector corresponding to the merge step in the CURLVLth step of the merge process with TLVLS steps for the CURPBMth problem.

🌸 Parameters 🌸

• N — N is INTEGER. The dimension of the symmetric tridiagonal matrix. N >= 0.
• TLVLS — TLVLS is INTEGER. The total number of merging levels in the overall divide and conquer tree.
• CURLVL — CURLVL is INTEGER. The current level in the overall merge routine, 0 <= curlvl <= tlvls.
• CURPBM — CURPBM is INTEGER. The current problem in the current level in the overall merge routine (counting from upper left to lower right).
• PRMPTR — PRMPTR is INTEGER array, dimension (N lg N). Contains a list of pointers which indicate where in PERM a level's permutation is stored. PRMPTR(i+1) - PRMPTR(i) indicates the size of the permutation and incidentally the size of the full, non-deflated problem.
• PERM — PERM is INTEGER array, dimension (N lg N). Contains the permutations (from deflation and sorting) to be applied to each eigenblock.
• GIVPTR — GIVPTR is INTEGER array, dimension (N lg N). Contains a list of pointers which indicate where in GIVCOL a level's Givens rotations are stored. GIVPTR(i+1) - GIVPTR(i) indicates the number of Givens rotations.
• GIVCOL — GIVCOL is INTEGER array, dimension (2, N lg N). Each pair of numbers indicates a pair of columns to take place in a Givens rotation.
• GIVNUM — GIVNUM is DOUBLE PRECISION array, dimension (2, N lg N). Each number indicates the S value to be used in the corresponding Givens rotation.
• Q — Q is DOUBLE PRECISION array, dimension (N**2). Contains the square eigenblocks from previous levels, the starting positions for blocks are given by QPTR.
• QPTR — QPTR is INTEGER array, dimension (N+2). Contains a list of pointers which indicate where in Q an eigenblock is stored. SQRT( QPTR(i+1) - QPTR(i) ) indicates the size of the block.
• Z — Z is DOUBLE PRECISION array, dimension (N). On output this vector contains the updating vector (the last row of the first sub-eigenvector matrix and the first row of the second sub-eigenvector matrix). it's giving main character output vector, honestly 👑
• ZTEMP — ZTEMP is DOUBLE PRECISION array, dimension (N). (that's it. that's the whole description. iconic minimalism 💅)
• INFO — INFO is INTEGER.
  • = 0: successful exit.
  • < 0: if INFO = -i, the i-th argument had an illegal value. so if info goes negative, somebody fed it a bad argument, go check argument number -INFO bestie 😭

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👑 Author 👑

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

🧚 Contributors: 🧚

Jeff Rutter, Computer Science Division, University of California at Berkeley, USA

Definition at line 164 of file dlaeda.f.

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🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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and that's the whole page! ✨ this beauty is from LAPACK, Version 3.12.0, straight out of /home/abui...RC/dlaeda.f(3) — no cap, go merge some eigenblocks, ily, bye 🎀💖🦋