TESTING/EIG/cget51.f(3)

💖 NAME 💖

okay bestie, welcome to the TESTING/EIG/cget51.f(3) page from the Library Functions Manual — this is the CGET51 subroutine and she is here to vibe-check a matrix decomposition. 💅

TESTING/EIG/cget51.f

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine cget51 (itype, n, a, lda, b, ldb, u, ldu, v, ldv, work, rwork, result)

CGET51

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🫶 Function/Subroutine Documentation 🫶

here's the full signature, copied exactly because we do not play with types around here:

subroutine cget51 (integer itype, integer n, complex, dimension( lda, * ) a,
    integer lda, complex, dimension( ldb, * ) b, integer ldb, complex,
    dimension( ldu, * ) u, integer ldu, complex, dimension( ldv, * ) v,
    integer ldv, complex, dimension( * ) work, real, dimension( * ) rwork,
    real result)

CGET51

🎯 Purpose 🎯

CGET51 generally checks a decomposition of the form

A = U B V**H

where **H means conjugate transpose and U and V are unitary.

Specifically, if ITYPE=1

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

If ITYPE=2, then:

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

If ITYPE=3, then:

RESULT = | I - U U**H | / ( n ulp )

🌸 Parameters 🌸

• ITYPE — INTEGER. Specifies the type of tests to be performed.
  • =1: RESULT = | A - U B V**H | / ( |A| n ulp )
  • =2: RESULT = | A - B | / ( |A| n ulp )
  • =3: RESULT = | I - U U**H | / ( n ulp )
• N — INTEGER. The size of the matrix. If it is zero, CGET51 does nothing. It must be at least zero.
• A — COMPLEX array, dimension (LDA, N). The original (unfactored) matrix.
• LDA — INTEGER. The leading dimension of A. It must be at least 1 and at least N.
• B — COMPLEX array, dimension (LDB, N). The factored matrix.
• LDB — INTEGER. The leading dimension of B. It must be at least 1 and at least N.
• U — COMPLEX array, dimension (LDU, N). The unitary matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2.
• LDU — INTEGER. The leading dimension of U. LDU must be at least N and at least 1.
• V — COMPLEX array, dimension (LDV, N). The unitary matrix on the left-hand side in the decomposition. Not referenced if ITYPE=2.
• LDV — INTEGER. The leading dimension of V. LDV must be at least N and at least 1.
• WORK — COMPLEX array, dimension (2*N**2).
• RWORK — REAL array, dimension (N).
• RESULT — REAL. 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 153 of file cget51.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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