Function RoundToEven

tensorflow/compiler/xla/client/lib/math.cc:1093–1112

Implements Banker's rounding: numbers that are equidistant between two integers are rounded towards even.

// Implements Banker's rounding: numbers that are equidistant between two
// integers are rounded towards even.
XlaOp RoundToEven(XlaOp x) {
  auto& b = *x.builder();
  return b.ReportErrorOrReturn([&]() -> StatusOr<XlaOp> {
    // Reject non-real non-fp inputs (What does it even mean to round a complex
    // number?  Do you round each component equally?  In that case, you should
    // just ask for that explicitly.)
    TF_RETURN_IF_ERROR(EnsureOperandIsRealFp("RoundToEven", x));

    auto half = ScalarLike(x, 0.5);
    auto one = ScalarLike(x, 1.0);
    auto two = ScalarLike(x, 2.0);

    auto round_val = Floor(x);
    auto fraction = x - round_val;
    auto nearest_even_int = round_val - two * Floor(half * x);
    auto is_odd = Eq(nearest_even_int, one);
    return Select(Or(Gt(fraction, half), And(Eq(fraction, half), is_odd)),
                  round_val + one, round_val);
  });
}

// Trigonometric functions.