template<class RooSet_t, std::size_t POOLSIZE>
class MemPoolForRooSets< RooSet_t, POOLSIZE >
Memory pool for RooArgSet and RooDataSet.
RooArgSet and RooDataSet were using a mempool that guarantees that allocating, de-allocating and re-allocating a set does not yield the same pointer. RooFit relies on this, unfortunately, because it compares the pointers of RooArgSets to figure out caching, e.g. of integrals.
Since both RooArgSet and RooDataSet were using the same logic to manage their memory pools, the functionality has been put here in a single place. The introduction of this common mempool also solved RooFit's static destruction order problems by letting arenas of the mempool leak if RooArgSets are still alive. This is necessary if the tear down of the mempool happens before all RooArgSets of the entire process have been deleted. This might e.g. happen in static configs for integrators or when a plot of a PDF is alive when quitting the interpreter.
If this memory pool seems to leak memory:
- It is likely a leaking RooArgSet / RooDataSet
- Disable the memory pool using the
#define in RooArgSet.h / RooDataSet.h
- Rerun the leak check to find the leaking RooXSet
- Fix it
- Re-enable the memory pool
- Warning
- Disabling the memory pools might seem to work at first sight, but can eventually lead to wrong computations. This would happen if the operating system decides to assign the same memory address when a RooArgSet is deleted and re-allocated, and both the deleted as well as the new set happen to be used in the same computation graph. RooFit will think that the cache doesn't have to be recalculated, and will return an outdated result. These errors are hard to track down, because they might only happen in a specific toy MC run on a specific OS / architecture.
How to get rid of the memory pool
If RooArgSet or RooDataSet were compared based on a unique ID instead of their pointer, this class would become obsolete. It should be tested, though, if handing memory management over to the OS has an impact on speed. This is less of a worry, though, because OSs got smarter over RooFit's life time.
Definition at line 60 of file MemPoolForRooSets.h.
