Function CheckPreprocessedTarget

catboost/libs/metrics/metric.cpp:7002–7035

}

void CheckPreprocessedTarget(
    TConstArrayRef<float> target,
    const NCatboostOptions::TLossDescription& lossDesciption,
    bool isNonEmptyAndNonConst,
    bool allowConstLabel
) {
    ELossFunction lossFunction = lossDesciption.GetLossFunction();
    if (isNonEmptyAndNonConst && (lossFunction != ELossFunction::PairLogit) && (lossFunction != ELossFunction::PairLogitPairwise)) {
        auto targetBounds = CalcMinMax(target);
        CB_ENSURE((targetBounds.Min != targetBounds.Max) || allowConstLabel, "All train targets are equal");
    }
    if (EqualToOneOf(lossFunction, ELossFunction::CrossEntropy, ELossFunction::PFound, ELossFunction::ERR)) {
        auto targetBounds = CalcMinMax(target);
        CB_ENSURE(targetBounds.Min >= 0, "Min target less than 0: " + ToString(targetBounds.Min));
        CB_ENSURE(targetBounds.Max <= 1, "Max target greater than 1: " + ToString(targetBounds.Max));
    }

    if (lossFunction == ELossFunction::QuerySoftMax) {
        float minTarget = *MinElement(target.begin(), target.end());
        CB_ENSURE(minTarget >= 0, "Min target less than 0: " + ToString(minTarget));
    }

    if (IsMultiClassOnlyMetric(lossFunction)) {
        CB_ENSURE(AllOf(target, [](float x) { return int(x) == x && x >= 0; }),
                  "metric/loss-function " << lossFunction << " is a Multiclassification metric, "
                  " each target label should be a nonnegative integer");
    }

    if (lossFunction != ELossFunction::MultiRMSEWithMissingValues) {
        for (auto objectIdx : xrange(target.size())){
            CB_ENSURE(!IsNan(target[objectIdx]), "metric/loss-function " << lossFunction << " does not allow nan values in target data");
        }
    }
}

static EMetricBestValue GetOptimumType(TStringBuf lossFunction) {
    const auto metric = CreateMetricsFromDescription({TString(lossFunction)}, /*approxDim*/ 1);