PhD Thesis - staffweb - University of Greenwich

PhD Thesis by John Ewer.considering a whole history of monitoring data and solution states. This consideration may alsobe of relevance to the purpose behind a particular simulation and the form that the results willtake. This is particularly important for transient simulations where the interest in not so muchin any final solution state or data but is rather in the critical phases and changes that occur duringthe full simulation. With reference to using fire modelling for assessing safety of the builtenvironment, it is insufficient to merely say that at the end of the simulation conditions in a roomfire were non-survivable when it would be of more use to determine the first time at which theroom fire became truly dangerous.4.3.7 Debugging facilitiesSince the code is intended to be used for algorithm development it was considered vital toprovide comprehensive debugging facilities. It is not sufficient to rely solely on compilerprovided debugging because the variability of such debuggers is very large and the navigationof complex data structures can be problematic and time consuming. In the prototype system twoseparate debugging facilities have been provided. The first allows any stored variable to beoutput in human readable form just after it has been calculated. This output can be limited to aparticular simulation time and range of cells. The second facility allows specific data monitoringcode to be planted in the data access functions. This allows the values of any data item to bemonitored throughout the simulation whenever data is accessed. Of course these techniques donot prevent a developer from using compiler debugging techniques but do provide additionaltools to track down hard to find errors that are a quite common occurrence when developingnew algorithms.4.3.8 Automatic self extending arraysSometimes it would be inefficient, in terms of memory usage, to allocate arrays to the maximumanticipated size when such arrays may only infrequently use their full extent. Conversely if thelength of an array is likely to change quite often then re-allocation is likely to be inefficient interms of performance because of the book-keeping involved with creating a larger array andmoving the existing elements across to it, followed by destruction of the old array space. There4-81