# EnsembleProblem: data saving and logging

**URL:** <https://discourse.julialang.org/t/ensembleproblem-data-saving-and-logging/66025>\
**Category:** Modelling & Simulations\
**Tags:** sciml\
**Created:** [August 8, 2021, 3:49pm UTC](https://discourse.julialang.org/t/ensembleproblem-data-saving-and-logging/66025 "2021-08-08T15:49:20Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Gregstrq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gregstrq/32/20620_2.png) [@Gregstrq](https://discourse.julialang.org/u/Gregstrq)\
**Post date:** [August 8, 2021, 3:49pm UTC](https://discourse.julialang.org/t/ensembleproblem-data-saving-and-logging/66025/1 "2021-08-08T15:49:20Z")

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Great job with the facilities for Monte Carlo Simulations.

I have a couple of question about `EnsembleProblem`. From the docs, it follows that the data from all the trajectories is saved. Is it possible to use [Welford’s online algorithm](https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm) to accumulate the data on the go (each batch would have its own accumulator)?

It is also convenient to be able to save to file accumulated results after each `n` trajectories. This way, the data can be analyzed in the background as the simulation still goes on. So, is it possible to do it?