BLAS/SRC/dtrsv.f(3)

✨ NAME ✨

okay so bestie, this page is literally about BLAS/SRC/dtrsv.f — like, that's the whole vibe of the NAME section, no notes. 💅

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🌸 SYNOPSIS 🌸

Functions/Subroutines

• subroutine dtrsv (uplo, trans, diag, n, a, lda, x, incx)
  • DTRSV — that's her, that's the icon. 👑

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💖 Function/Subroutine Documentation 💖

subroutine dtrsv

Here's the full signature, character for character, don't @ me:

subroutine dtrsv (character uplo, character trans, character diag, integer
    n, double precision, dimension(lda,*) a, integer lda, double precision,
    dimension(*) x, integer incx)

DTRSV 🫶

🎯 Purpose:

ok so DTRSV solves one of these systems of equations, and it's giving triangular realness:

A*x = b,   or   A**T*x = b,

where b and x are n element vectors and A is an n by n unit, or non-unit, upper or lower triangular matrix.

🚨 bestie listen. No test for singularity or near-singularity is included in this routine. Such tests must be performed before calling this routine. She will NOT warn you. She will simply do the thing. 😭

🎀 Parameters

• UPLO — UPLO is CHARACTER*1
  • On entry, UPLO specifies whether the matrix is an upper or lower triangular matrix as follows:
    • UPLO = 'U' or 'u' → A is an upper triangular matrix.
    • UPLO = 'L' or 'l' → A is a lower triangular matrix.
• TRANS — TRANS is CHARACTER*1
  • On entry, TRANS specifies the equations to be solved as follows:
    • TRANS = 'N' or 'n' → A*x = b.
    • TRANS = 'T' or 't' → A**T*x = b.
    • TRANS = 'C' or 'c' → A**T*x = b.
• DIAG — DIAG is CHARACTER*1
  • On entry, DIAG specifies whether or not A is unit triangular as follows:
    • DIAG = 'U' or 'u' → A is assumed to be unit triangular.
    • DIAG = 'N' or 'n' → A is not assumed to be unit triangular.
• N — N is INTEGER
  • On entry, N specifies the order of the matrix A. N must be at least zero.
• A — A is DOUBLE PRECISION array, dimension ( LDA, N )
  • Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array A must contain the upper triangular matrix and the strictly lower triangular part of A is not referenced.
  • Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular matrix and the strictly upper triangular part of A is not referenced.
  • Note that when DIAG = 'U' or 'u', the diagonal elements of A are not referenced either, but are assumed to be unity.
• LDA — LDA is INTEGER
  • On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least max( 1, n ).
• X — X is DOUBLE PRECISION array, dimension at least ( 1 + ( n - 1 )*abs( INCX ) )
  • Before entry, the incremented array X must contain the n element right-hand side vector b. On exit, X is overwritten with the solution vector x.
• INCX — INCX is INTEGER
  • On entry, INCX specifies the increment for the elements of X. INCX must not be zero.

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Level 2 Blas routine. -- Written on 22-October-1986. Jack Dongarra, Argonne National Lab. Jeremy Du Croz, Nag Central Office. Sven Hammarling, Nag Central Office. Richard Hanson, Sandia National Labs.

the way this routine has been iconic since 1986 and is still serving... main character energy fr fr. 💜

👑 Author

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

Definition at line 142 of file dtrsv.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 bestie, no crumbs left 🍓 — this was Version 3.12.0, dated Tue Nov 28 2023 12:08:41, and the file is BLAS/SRC/dtrsv.f(3). slay, go solve some triangular systems 💅✨🦋