@SGaist

Thanks for the quick reply.

Until a few days ago the data was held in a QList <MyClass>. The data is supposed to arrive already sorted by date-time, but there are exceptions. The the QList::sort() method was just too slow so I tried converting to a QMultiMap to insert the data by QDateTime. This involved a tolerable amount of change to the code.

Changing back, could I change QMap <QDateTime, MyClass> to QList <MyClass>
and use std::stable_sort(dataList.toStd.begin(), dataList.toStd.end(), MyClass::less)?

The MyClass < method is already available in place, so that's not an issue. It wasn't obvious to me that QList::toStd() would produce a reference to the underlying list letting me sort in place with std::stable_sort.

Anyway, I have changed the data storage to a std:vector and use std::stable_sort because sorting on a std::vector is so much faster than on a std::list.

The old qStableSort was very fast on a QList, so I'm sure the QT designers were taking advantage of the way a QList is stored. I guess I jumped the gun on removing deprecated features.

Ken