The Nimrod Toolset
Dr Tom Peachey, Nimrod expert and Melbourne-based consultant
Researchers increasingly use computational models to supplement or even replace, experiments with the real world system. These computational models are typically computationally expensive, requiring hours or even days for a single job. And researchers usually need to run the model many times to explore the effects of variation of the input parameters, “parametric computing”. Nimrod was developed to expedite such experiments by sending jobs for concurrent execution on a cluster of processors or to the resources of a computational grid.
It soon became apparent that the aim in many such experiments was to optimise some aspect of the model output. To facilitate this, a variant called Nimrod/O was developed that offered a variety of optimisation algorithms, seamlessly interfacing them with the Nimrod distributed execution capacity. A researcher could supply a computational model, create a simple plan file specifying the experiment and the optimisation method(s) and wait for the results. Nimrod/OI was an interactive version that enabled human interaction and hence optimisation of subjective characters.
When there are several parameters each with a range of values allowed, a full sweep over all possible combinations becomes prohibitive. Nimrod/E incorporates experimental designs that organise the experiment with a parsimonious number of jobs required.
Traditional Nimrod, like most applications, may appear monolithic, just “plan in” and “results out”. By contrast, Nimrod/K is a workflow engine; the user assembles and connects various components on a graphical interface. This enables the user to create novel tools and to monitor information flowing between components.
This talk will show many examples of the use of these tools, taken from 15 years of deployment.
Tom is a mathematician with an interest in computational modelling. He spent 11 years working on the Nimrod suite of tools. He now alternates between Australia and Thailand still thinking about Nimrod.