private unsafe double Eval(int dataIdx)
{
if (!_hasMetric)
return double.NaN;
int outLen = 0;
double[] res = new double[1];
fixed (double* ptr = res)
PInvokeException.Check(PInvoke.BoosterGetEval(Handle, dataIdx, ref outLen, ptr),
nameof(PInvoke.BoosterGetEval));
return res[0];
}