SRC/sopmtr.f(3)

✨ SRC/sopmtr.f(3) ✨

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💖 NAME 💖

SRC/sopmtr.f

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🌸 SYNOPSIS 🌸

🧚 Functions/Subroutines 🧚

subroutine sopmtr (side, uplo, trans, m, n, ap, tau, c, ldc, work, info)
    SOPMTR

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🌈 Function/Subroutine Documentation 🌈

subroutine sopmtr (character side, character uplo, character trans, integer
     m, integer n, real, dimension( * ) ap, real, dimension( * ) tau, real,
     dimension( ldc, * ) c, integer ldc, real, dimension( * ) work, integer
     info)

SOPMTR — here's the whole function tea, no gatekeeping:

🎯 Purpose 🎯

SOPMTR overwrites the general real M-by-N matrix C with:

                SIDE = 'L'     SIDE = 'R'
TRANS = 'N':      Q * C          C * Q
TRANS = 'T':      Q**T * C       C * Q**T

where Q is a real orthogonal matrix of order nq, with nq = m if SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of nq-1 elementary reflectors, as returned by SSPTRD using packed storage:

if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);

if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).

🎛️ Parameters 🎛️

• SIDE — SIDE is CHARACTER*1.
  • = 'L': apply Q or Q**T from the Left;
  • = 'R': apply Q or Q**T from the Right.
• UPLO — UPLO is CHARACTER*1.
  • = 'U': Upper triangular packed storage used in previous call to SSPTRD;
  • = 'L': Lower triangular packed storage used in previous call to SSPTRD.
• TRANS — TRANS is CHARACTER*1.
  • = 'N': No transpose, apply Q;
  • = 'T': Transpose, apply Q**T.
• M — M is INTEGER. The number of rows of the matrix C. M >= 0.
• N — N is INTEGER. The number of columns of the matrix C. N >= 0.
• AP — AP is REAL array, dimension (M*(M+1)/2) if SIDE = 'L' (N*(N+1)/2) if SIDE = 'R'. The vectors which define the elementary reflectors, as returned by SSPTRD. AP is modified by the routine but restored on exit.
• TAU — TAU is REAL array, dimension (M-1) if SIDE = 'L' or (N-1) if SIDE = 'R'. TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SSPTRD.
• C — C is REAL array, dimension (LDC,N). On entry, the M-by-N matrix C. On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
• LDC — LDC is INTEGER. The leading dimension of the array C. LDC >= max(1,M).
• WORK — WORK is REAL array, dimension (N) if SIDE = 'L' (M) if SIDE = 'R'.
• INFO — INFO is INTEGER.
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

👑 Author 👑

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

Definition at line 148 of file sopmtr.f.

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👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

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