TESTING/EIG/dget51.f(3)

🎀 TESTING/EIG/dget51.f 🎀

Welcome to the Library Functions Manual, bestie — today's page is all about TESTING/EIG/dget51.f. It's giving “test helper for eigendecomposition vibes,” and we're gonna read it together. 💅

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✨ NAME ✨

TESTING/EIG/dget51.f

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🦋 SYNOPSIS 🦋

🧚 Functions/Subroutines 🧚

subroutine dget51 (itype, n, a, lda, b, ldb, u, ldu, v, ldv, work,
           result)

DGET51 — yes, that's the subroutine's name. Iconic. 💖

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💅 Function/Subroutine Documentation 💅

subroutine dget51 (integer itype, integer n, double precision, dimension(
       lda, * ) a, integer lda, double precision, dimension( ldb, * ) b,
       integer ldb, double precision, dimension( ldu, * ) u, integer ldu,
       double precision, dimension( ldv, * ) v, integer ldv, double precision,
       dimension( * ) work, double precision result)

DGET51

🍓 Purpose 🍓

DGET51 generally checks a decomposition of the form

A = U B V'

where ' means transpose and U and V are orthogonal.

Specifically, if ITYPE=1:

RESULT = | A - U B V' | / ( |A| n ulp )

If ITYPE=2, then:

RESULT = | A - B | / ( |A| n ulp )

If ITYPE=3, then:

RESULT = | I - UU' | / ( n ulp )

🌈 Parameters 🌈

• ITYPE — ITYPE is INTEGER. Specifies the type of tests to be performed.
  • =1: RESULT = | A - U B V' | / ( |A| n ulp )
  • =2: RESULT = | A - B | / ( |A| n ulp )
  • =3: RESULT = | I - UU' | / ( n ulp )
• N — N is INTEGER. The size of the matrix. If it is zero, DGET51 does nothing. It must be at least zero.
• A — A is DOUBLE PRECISION array, dimension (LDA, N). The original (unfactored) matrix.
• LDA — LDA is INTEGER. The leading dimension of A. It must be at least 1 and at least N.
• B — B is DOUBLE PRECISION array, dimension (LDB, N). The factored matrix.
• LDB — LDB is INTEGER. The leading dimension of B. It must be at least 1 and at least N.
• U — U is DOUBLE PRECISION array, dimension (LDU, N). The orthogonal matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2.
• LDU — LDU is INTEGER. The leading dimension of U. LDU must be at least N and at least 1.
• V — V is DOUBLE PRECISION array, dimension (LDV, N). The orthogonal matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2.
• LDV — LDV is INTEGER. The leading dimension of V. LDV must be at least N and at least 1.
• WORK — WORK is DOUBLE PRECISION array, dimension (2*N**2).
• RESULT — RESULT is DOUBLE PRECISION. The values computed by the test specified by ITYPE. The value is currently limited to 1/ulp, to avoid overflow. Errors are flagged by RESULT=10/ulp.

👑 Author 👑

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

Definition: Definition at line 147 of file dget51.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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That's the tea, bestie: LAPACK Version 3.12.0, source TESTING/EIG/dget51.f(3). Byeee 💖✨