The flags directory conveys information about the status of each calculation and can be used to check for when the calculation has completed, but it conveys no information on the resource usage of the calculation. The CPU usage, memory usage and read/write speed of the calculation over time is of particular importance to both users of computational chemistry and designers of new software, as it helps to identify 'bottlenecks' (i.e., the slow part) of a calculation, and to diagnose out-of-memory failures. Digichem provides calculation profiling for all of its supported calculation engines, and records the following information: 1) CPU usage; 2) real; and 3) virtual memory usage; 4) total number of bytes read from the file system; 5) instantaneous read speed; 6) total number of bytes written to the file system; 7) instantaneous write speed; and 8) the number of new processes spawned since the last profiling step. This information is continuously logged to a CSV file as the calculation progresses, so it can be inspected even before the calculation has completed, and the profiling frequency can be manually adjusted to favour either higher resolution (more profiling steps) or lower file size (fewer profiling steps). The CPU and memory statistics for an example optimisation calculation are shown graphically in Figure , which clearly details the short, large decreases in CPU usage surrounding a new energy calculation step starting.