dtplqt function

Implementation

void dtplqt(
  final int M,
  final int N,
  final int L,
  final int MB,
  final Matrix<double> A_,
  final int LDA,
  final Matrix<double> B_,
  final int LDB,
  final Matrix<double> T_,
  final int LDT,
  final Array<double> WORK_,
  final Box<int> INFO,
) {
  final A = A_.having(ld: LDA);
  final B = B_.having(ld: LDB);
  final T = T_.having(ld: LDT);
  final WORK = WORK_.having();

  // Test the input arguments
  INFO.value = 0;
  if (M < 0) {
    INFO.value = -1;
  } else if (N < 0) {
    INFO.value = -2;
  } else if (L < 0 || (L > min(M, N) && min(M, N) >= 0)) {
    INFO.value = -3;
  } else if (MB < 1 || (MB > M && M > 0)) {
    INFO.value = -4;
  } else if (LDA < max(1, M)) {
    INFO.value = -6;
  } else if (LDB < max(1, M)) {
    INFO.value = -8;
  } else if (LDT < MB) {
    INFO.value = -10;
  }
  if (INFO.value != 0) {
    xerbla('DTPLQT', -INFO.value);
    return;
  }

  // Quick return if possible
  if (M == 0 || N == 0) return;

  for (var I = 1; I <= M; I += MB) {
    // Compute the QR factorization of the current block
    final IB = min(M - I + 1, MB);
    final NB = min(N - L + I + IB - 1, N);
    final int LB;
    if (I >= L) {
      LB = 0;
    } else {
      LB = NB - N + L - I + 1;
    }

    dtplqt2(IB, NB, LB, A(I, I), LDA, B(I, 1), LDB, T(1, I), LDT, Box(0));

    // Update by applying H**T to B(I+IB:M,:) from the right
    if (I + IB <= M) {
      dtprfb(
        'R',
        'N',
        'F',
        'R',
        M - I - IB + 1,
        NB,
        IB,
        LB,
        B(I, 1),
        LDB,
        T(1, I),
        LDT,
        A(I + IB, I),
        LDA,
        B(I + IB, 1),
        LDB,
        WORK.asMatrix(M - I - IB + 1),
        M - I - IB + 1,
      );
    }
  }
}