Fix floating point comparison in the tests

[dmitriy-sobolev]

oneDPL/test/support/utils.h

Lines 115 to 125 in 59c96c8

	template <typename T1, typename T2>
	bool
	is_equal_val(const T1& val1, const T2& val2)
	{
	using T = std::common_type_t<T1, T2>;
	if constexpr (std::is_floating_point_v<T>)
	{
	const auto eps = std::numeric_limits<T>::epsilon();
	return std::fabs(T(val1) - T(val2)) < eps;
	}

This floating point comparison approach is not correct.
Instead we should:

1. Numeric algorithms: create a "stretching" margin of error.
2. Rest algorithms, i.e. ones which just move and shuffle elements: compare values exactly.

There was an attempt to do (1) in #2762, but it was reverted as a non-essential change:

template <typename T>
bool
is_close(T a, T b)
{
    // abs_tol is for rounding errors near zero.
    // It is a multiple of an epsilon to tolerate accumulated errors.
    // The larger the type, the larger the multiple to allow for more accumulations.
    // rel_tol is selected intuitively.
    T rel_tol = T(0.001); // 0.1%
    T abs_tol = T(1e-5); // ~100x of the epsilon for float
    if constexpr (sizeof(T) > sizeof(float))
    {
        rel_tol = T(0.0001); // 0.01%, 10x of the relative difference of any nearest number
        abs_tol = T(1e-12); // ~1000x of the epsilon
    }
#if TEST_DPCPP_BACKEND_PRESENT
    else if constexpr (std::is_same_v<T, sycl::half>)
    {
        rel_tol = T(0.005); // 0.5%
        abs_tol = T(1e-3); // ~10x of the epsilon
    }
#if defined(SYCL_IMPLEMENTATION_INTEL)
    else if constexpr (std::is_same_v<T, sycl::ext::oneapi::bfloat16>)
    {
        rel_tol = T(0.02); // 2%
        abs_tol = T(1e-2); // ~10x of the epsilon
    }
#endif
#endif
    const T tol = std::max(rel_tol * std::max(std::fabs(a), std::fabs(b)), abs_tol);
    return std::fabs(a - b) < tol;
}

template <typename T>
constexpr bool is_non_standard_float_v = false;

#if TEST_DPCPP_BACKEND_PRESENT
template <>
constexpr bool is_non_standard_float_v<sycl::half> = true;
#if defined(SYCL_IMPLEMENTATION_INTEL)
template <>
constexpr bool is_non_standard_float_v<sycl::ext::oneapi::bfloat16> = true;
#endif
#endif