TESTING/LIN/strt02.f(3)

💅 TESTING/LIN/strt02.f(3)

okay so bestie, this page is from the Library Functions Manual and it's all about strt02 — a subroutine that checks residuals for triangular solves. iykyk. it's giving LAPACK test energy, not main-character app energy.

🌸 NAME

TESTING/LIN/strt02.f

🎀 SYNOPSIS

✨ Functions/Subroutines

subroutine strt02 (uplo, trans, diag, n, nrhs, a, lda, x, ldx, b, ldb,
           work, resid)
           STRT02

🦋 Function/Subroutine Documentation

subroutine strt02 (character uplo, character trans, character diag, integer
           n, integer nrhs, real, dimension( lda, * ) a, integer lda, real,
           dimension( ldx, * ) x, integer ldx, real, dimension( ldb, * ) b, integer
           ldb, real, dimension( * ) work, real resid)
           STRT02

💖 Purpose

okay so STRT02 computes the residual for the computed solution to a triangular system of linear equations op(A)*X = B, where A is a triangular matrix. no cap. The test ratio is the maximum over:

norm(b - op(A)*x) / ( ||op(A)||_1 * norm(x) * EPS ),

where op(A) = A or A**T, b is the column of B, x is the solution vector, and EPS is the machine epsilon. The norm used is the 1-norm. periodt. 💅

🎀 Parameters

• UPLO — CHARACTER*1. tells you if the matrix A is upper or lower triangular, bestie.
  • 'U': Upper triangular
  • 'L': Lower triangular
• TRANS — CHARACTER*1. says which operation is applied to A.
  • 'N': A * X = B (No transpose)
  • 'T': A**T * X = B (Transpose)
  • 'C': A**H * X = B (Conjugate transpose = Transpose)
• DIAG — CHARACTER*1. tells you whether or not the matrix A is unit triangular.
  • 'N': Non-unit triangular
  • 'U': Unit triangular
• N — INTEGER. the order of the matrix A. N >= 0.
• NRHS — INTEGER. the number of right hand sides, i.e., the number of columns of the matrices X and B. NRHS >= 0.
• A — REAL array, dimension (LDA,N). the triangular matrix A. If UPLO = 'U', the leading n by n upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1. 🫶
• LDA — INTEGER. the leading dimension of the array A. LDA >= max(1,N).
• X — REAL array, dimension (LDX,NRHS). the computed solution vectors for the system of linear equations.
• LDX — INTEGER. the leading dimension of the array X. LDX >= max(1,N).
• B — REAL array, dimension (LDB,NRHS). the right hand side vectors for the system of linear equations.
• LDB — INTEGER. the leading dimension of the array B. LDB >= max(1,N).
• WORK — REAL array, dimension (N). that's the whole note, bestie.
• RESID — REAL. the maximum over the number of right hand sides of:

norm(op(A)*X - B) / ( norm(op(A)) * norm(X) * EPS ).

💫 Author

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

Definition at line 148 of file strt02.f.

👑 Author

Generated automatically by Doxygen for LAPACK from the source code.

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sending kisses and slay vibes from the Library Functions Manual — footer energy: LAPACK Version 3.12.0, page TESTING/LIN/strt02.f(3) (no date line in this snippet, so that's all we got) 💜✨