dtfttp function

Implementation

void dtfttp(
  final String TRANSR,
  final String UPLO,
  final int N,
  final Array<double> ARF_,
  final Array<double> AP_,
  final Box<int> INFO,
) {
  final ARF = ARF_.having(offset: zeroIndexedArrayOffset);
  final AP = AP_.having(offset: zeroIndexedArrayOffset);

  bool LOWER, NISODD, NORMALTRANSR;
  int N1, N2, K = 0;
  int I, J, IJ;
  int IJP, JP, LDA, JS;

  // Test the input parameters.

  INFO.value = 0;
  NORMALTRANSR = lsame(TRANSR, 'N');
  LOWER = lsame(UPLO, 'L');
  if (!NORMALTRANSR && !lsame(TRANSR, 'T')) {
    INFO.value = -1;
  } else if (!LOWER && !lsame(UPLO, 'U')) {
    INFO.value = -2;
  } else if (N < 0) {
    INFO.value = -3;
  }
  if (INFO.value != 0) {
    xerbla('DTFTTP', -INFO.value);
    return;
  }

  // Quick return if possible

  if (N == 0) return;

  if (N == 1) {
    if (NORMALTRANSR) {
      AP[0] = ARF[0];
    } else {
      AP[0] = ARF[0];
    }
    return;
  }

  // Set N1 and N2 depending on LOWER

  if (LOWER) {
    N2 = N ~/ 2;
    N1 = N - N2;
  } else {
    N1 = N ~/ 2;
    N2 = N - N1;
  }

  // If N is odd, set NISODD = true;
  // If N is even, set K = N/2 and NISODD = false;

  // set lda of ARF^C; ARF^C is (0:(N+1)/2-1,0:N-noe)
  // where noe = 0 if n is even, noe = 1 if n is odd

  if ((N % 2) == 0) {
    K = N ~/ 2;
    NISODD = false;
    LDA = N + 1;
  } else {
    NISODD = true;
    LDA = N;
  }

  // ARF^C has lda rows and n+1-noe cols

  if (!NORMALTRANSR) LDA = (N + 1) ~/ 2;

  // start execution: there are eight cases

  if (NISODD) {
    // N is odd

    if (NORMALTRANSR) {
      // N is odd and TRANSR = 'N'

      if (LOWER) {
        // SRPA for LOWER, NORMAL and N is odd ( a(0:n-1,0:n1-1) )
        // T1 -> a(0,0), T2 -> a(0,1), S -> a(n1,0)
        // T1 -> a(0), T2 -> a(n), S -> a(n1); lda = n

        IJP = 0;
        JP = 0;
        for (J = 0; J <= N2; J++) {
          for (I = J; I <= N - 1; I++) {
            IJ = I + JP;
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JP += LDA;
        }
        for (I = 0; I <= N2 - 1; I++) {
          for (J = 1 + I; J <= N2; J++) {
            IJ = I + J * LDA;
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
      } else {
        // SRPA for UPPER, NORMAL and N is odd ( a(0:n-1,0:n2-1)
        // T1 -> a(n1+1,0), T2 -> a(n1,0), S -> a(0,0)
        // T1 -> a(n2), T2 -> a(n1), S -> a(0)

        IJP = 0;
        for (J = 0; J <= N1 - 1; J++) {
          IJ = N2 + J;
          for (I = 0; I <= J; I++) {
            AP[IJP] = ARF[IJ];
            IJP++;
            IJ += LDA;
          }
        }
        JS = 0;
        for (J = N1; J <= N - 1; J++) {
          IJ = JS;
          for (IJ = JS; IJ <= JS + J; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA;
        }
      }
    } else {
      // N is odd and TRANSR = 'T'

      if (LOWER) {
        // SRPA for LOWER, TRANSPOSE and N is odd
        // T1 -> A(0,0) , T2 -> A(1,0) , S -> A(0,n1)
        // T1 -> a(0+0) , T2 -> a(1+0) , S -> a(0+n1*n1); lda=n1

        IJP = 0;
        for (I = 0; I <= N2; I++) {
          for (IJ = I * (LDA + 1); IJ <= N * LDA - 1; IJ += LDA) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
        JS = 1;
        for (J = 0; J <= N2 - 1; J++) {
          for (IJ = JS; IJ <= JS + N2 - J - 1; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA + 1;
        }
      } else {
        // SRPA for UPPER, TRANSPOSE and N is odd
        // T1 -> A(0,n1+1), T2 -> A(0,n1), S -> A(0,0)
        // T1 -> a(n2*n2), T2 -> a(n1*n2), S -> a(0); lda = n2

        IJP = 0;
        JS = N2 * LDA;
        for (J = 0; J <= N1 - 1; J++) {
          for (IJ = JS; IJ <= JS + J; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA;
        }
        for (I = 0; I <= N1; I++) {
          for (IJ = I; IJ <= I + (N1 + I) * LDA; IJ += LDA) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
      }
    }
  } else {
    // N is even

    if (NORMALTRANSR) {
      // N is even and TRANSR = 'N'

      if (LOWER) {
        // SRPA for LOWER, NORMAL, and N is even ( a(0:n,0:k-1) )
        // T1 -> a(1,0), T2 -> a(0,0), S -> a(k+1,0)
        // T1 -> a(1), T2 -> a(0), S -> a(k+1)

        IJP = 0;
        JP = 0;
        for (J = 0; J <= K - 1; J++) {
          for (I = J; I <= N - 1; I++) {
            IJ = 1 + I + JP;
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JP += LDA;
        }
        for (I = 0; I <= K - 1; I++) {
          for (J = I; J <= K - 1; J++) {
            IJ = I + J * LDA;
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
      } else {
        // SRPA for UPPER, NORMAL, and N is even ( a(0:n,0:k-1) )
        // T1 -> a(k+1,0) ,  T2 -> a(k,0),   S -> a(0,0)
        // T1 -> a(k+1), T2 -> a(k), S -> a(0)

        IJP = 0;
        for (J = 0; J <= K - 1; J++) {
          IJ = K + 1 + J;
          for (I = 0; I <= J; I++) {
            AP[IJP] = ARF[IJ];
            IJP++;
            IJ += LDA;
          }
        }
        JS = 0;
        for (J = K; J <= N - 1; J++) {
          IJ = JS;
          for (IJ = JS; IJ <= JS + J; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA;
        }
      }
    } else {
      // N is even and TRANSR = 'T'

      if (LOWER) {
        // SRPA for LOWER, TRANSPOSE and N is even (see paper)
        // T1 -> B(0,1), T2 -> B(0,0), S -> B(0,k+1)
        // T1 -> a(0+k), T2 -> a(0+0), S -> a(0+k*(k+1)); lda=k

        IJP = 0;
        for (I = 0; I <= K - 1; I++) {
          for (IJ = I + (I + 1) * LDA; IJ <= (N + 1) * LDA - 1; IJ += LDA) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
        JS = 0;
        for (J = 0; J <= K - 1; J++) {
          for (IJ = JS; IJ <= JS + K - J - 1; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA + 1;
        }
      } else {
        // SRPA for UPPER, TRANSPOSE and N is even (see paper)
        // T1 -> B(0,k+1),     T2 -> B(0,k),   S -> B(0,0)
        // T1 -> a(0+k*(k+1)), T2 -> a(0+k*k), S -> a(0+0)); lda=k

        IJP = 0;
        JS = (K + 1) * LDA;
        for (J = 0; J <= K - 1; J++) {
          for (IJ = JS; IJ <= JS + J; IJ++) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
          JS += LDA;
        }
        for (I = 0; I <= K - 1; I++) {
          for (IJ = I; IJ <= I + (K + I) * LDA; IJ += LDA) {
            AP[IJP] = ARF[IJ];
            IJP++;
          }
        }
      }
    }
  }
}