TheRock/rocm-libraries/projects/miopen/driver/calcerr.hpp

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#ifndef GUARD_CALC_ERR_
#define GUARD_CALC_ERR_

#include <cmath>
#include <cstdint>

// This works well when difference is small. When one value
// is 0 and another is not, result is incorrect (very big)
// due to zero exponent in one number and non-zero exponent
// in another, because exponent resides in MSBs of a floating
// point number.
template <typename T_>
float ApproxUlps(T_ c_val, T_ g_val)
{
    double err = -1.0;
    if(sizeof(T_) == 2)
    {
        int16_t* c_uval = reinterpret_cast<int16_t*>(&c_val);
        int16_t* g_uval = reinterpret_cast<int16_t*>(&g_val);
        err             = static_cast<double>(std::abs(*c_uval - *g_uval));
    }
    else if(sizeof(T_) == 4)
    {
        int32_t* c_uval = reinterpret_cast<int32_t*>(&c_val);
        int32_t* g_uval = reinterpret_cast<int32_t*>(&g_val);
        err             = static_cast<double>(std::abs(*c_uval - *g_uval));
    }
    else if(sizeof(T_) == 8)
    {
        int64_t* c_uval = reinterpret_cast<int64_t*>(&c_val);
        int64_t* g_uval = reinterpret_cast<int64_t*>(&g_val);
        err             = static_cast<double>(std::abs(*c_uval - *g_uval));
    }

    // double delta = abs(c_val - g_val);
    // double nextafter_delta = nextafterf(min(abs(c_val), abs(g_val)), (T_)INFINITY) -
    // min(abs(c_val), abs(g_val));
    // err = delta / nextafter_delta;
    return err;
}

#endif // GUARD_GUARD_CALC_ERR_