dgemm function

void dgemm(String TRANSA, String TRANSB, int M, int N, int K, double ALPHA, Matrix<double> A_, int LDA, Matrix<double> B_, int LDB, double BETA, Matrix<double> C_, int LDC,)

Implementation

void dgemm(
  final String TRANSA,
  final String TRANSB,
  final int M,
  final int N,
  final int K,
  final double ALPHA,
  final Matrix<double> A_,
  final int LDA,
  final Matrix<double> B_,
  final int LDB,
  final double BETA,
  final Matrix<double> C_,
  final int LDC,
) {
  final A = A_.having(ld: LDA);
  final B = B_.having(ld: LDB);
  final C = C_.having(ld: LDC);
  const ONE = 1.0, ZERO = 0.0;

  // Set  NOTA  and  NOTB  as  true if  A  and  B  respectively are not
  // transposed and set  NROWA and NROWB  as the number of rows of  A
  // and  B  respectively.

  final NOTA = lsame(TRANSA, 'N');
  final NOTB = lsame(TRANSB, 'N');
  final NROWA = NOTA ? M : K;
  final NROWB = NOTB ? K : N;

  // Test the input parameters.

  var INFO = 0;
  if (!NOTA && !lsame(TRANSA, 'C') && !lsame(TRANSA, 'T')) {
    INFO = 1;
  } else if (!NOTB && !lsame(TRANSB, 'C') && !lsame(TRANSB, 'T')) {
    INFO = 2;
  } else if (M < 0) {
    INFO = 3;
  } else if (N < 0) {
    INFO = 4;
  } else if (K < 0) {
    INFO = 5;
  } else if (LDA < max(1, NROWA)) {
    INFO = 8;
  } else if (LDB < max(1, NROWB)) {
    INFO = 10;
  } else if (LDC < max(1, M)) {
    INFO = 13;
  }
  if (INFO != 0) {
    xerbla('DGEMM', INFO);
    return;
  }

  // Quick return if possible.

  if ((M == 0) ||
      (N == 0) ||
      (((ALPHA == ZERO) || (K == 0)) && (BETA == ONE))) {
    return;
  }

  // And if  alpha == zero.

  if (ALPHA == ZERO) {
    if (BETA == ZERO) {
      for (var J = 1; J <= N; J++) {
        for (var I = 1; I <= M; I++) {
          C[I][J] = ZERO;
        }
      }
    } else {
      for (var J = 1; J <= N; J++) {
        for (var I = 1; I <= M; I++) {
          C[I][J] *= BETA;
        }
      }
    }
    return;
  }

  // Start the operations.

  if (NOTB) {
    if (NOTA) {
      // Form  C := alpha*A*B + beta*C.

      for (var J = 1; J <= N; J++) {
        if (BETA == ZERO) {
          for (var I = 1; I <= M; I++) {
            C[I][J] = ZERO;
          }
        } else if (BETA != ONE) {
          for (var I = 1; I <= M; I++) {
            C[I][J] *= BETA;
          }
        }
        for (var L = 1; L <= K; L++) {
          final TEMP = ALPHA * B[L][J];
          for (var I = 1; I <= M; I++) {
            C[I][J] += TEMP * A[I][L];
          }
        }
      }
    } else {
      // Form  C := alpha*A**T*B + beta*C

      for (var J = 1; J <= N; J++) {
        for (var I = 1; I <= M; I++) {
          var TEMP = ZERO;
          for (var L = 1; L <= K; L++) {
            TEMP += A[L][I] * B[L][J];
          }
          if (BETA == ZERO) {
            C[I][J] = ALPHA * TEMP;
          } else {
            C[I][J] = ALPHA * TEMP + BETA * C[I][J];
          }
        }
      }
    }
  } else {
    if (NOTA) {
      // Form  C := alpha*A*B**T + beta*C

      for (var J = 1; J <= N; J++) {
        if (BETA == ZERO) {
          for (var I = 1; I <= M; I++) {
            C[I][J] = ZERO;
          }
        } else if (BETA != ONE) {
          for (var I = 1; I <= M; I++) {
            C[I][J] *= BETA;
          }
        }
        for (var L = 1; L <= K; L++) {
          final TEMP = ALPHA * B[J][L];
          for (var I = 1; I <= M; I++) {
            C[I][J] += TEMP * A[I][L];
          }
        }
      }
    } else {
      // Form  C := alpha*A**T*B**T + beta*C

      for (var J = 1; J <= N; J++) {
        for (var I = 1; I <= M; I++) {
          var TEMP = ZERO;
          for (var L = 1; L <= K; L++) {
            TEMP += A[L][I] * B[J][L];
          }
          if (BETA == ZERO) {
            C[I][J] = ALPHA * TEMP;
          } else {
            C[I][J] = ALPHA * TEMP + BETA * C[I][J];
          }
        }
      }
    }
  }
}