Authors may post the final draft of their work on open, unrestricted Internet sites or deposit it in an institutional repository when the draft contains a link to the bibliographic record of the published version in the ASCE Civil Engineering Database. "Final draft" means the version submitted to ASCE after peer review and prior to copyediting or other ASCE production activities; it does not include the copyedited version, the page proof, or a PDF of the published version. Journal of Water Resources Planning and ManagementCitation: Elhay, S., Simpson, A.R., Deuerlein, J., Alexander, B. and Schilders, W.H.A., (2014). "Reformulated Co-tree flows method competitive with the Global Gradient Algorithm for solving the water distribution system equations. implementation. 7In this paper a Reformulated Co-Trees Method (RCTM) is presented that simplifies the pro-8 cedure by manipulating the incidence matrix into trapezoidal form: a lower triangular block at 9 the top representing a spanning tree and rectangular block below it representing the corresponding 10 co-tree. This reordering leads to significant efficiencies which make the RCTM competitive with 11 the GGA in certain settings. 12The new method has some similarities to the Loop Flows Corrections formulation and it is is shown, by application to a set of eight case study networks with between 932 and 19,647 pipes 14 and between 848 and 17971 nodes, to be between 15% and 82% faster than the GGA in a setting, be possible for the GGA in the same computing environment. 20Unlike some alternatives to the GGA, the following features, make the RCTM attractive: (i) 21it does not require a set of initial flows which satisfy continuity, (ii) there is no need to identify 22 independent loops or the loops incidence matrix, (iii) a spanning tree and co-tree can be found from 23 the incidence matrix without the addition of virtual loops, particularly when multiple reservoirs are 24 present, (iv) it does not require the addition of a ground node and pseudo-loops for each demand 25 node and does not require the determination of cut-sets. 26In contrast to the GGA, the RCTM does not require special techniques to handle zero flow 27 problems which can occur when the head loss is modeled by the Hazen-Williams formula (a sufficient 28 condition is given).

Defects are a major concern in software systems. Unsurprisingly, there are many tools and techniques to facilitate the removal of defects through their detection and localisation. However, there are few tools that attempt to repair defects. To date, evolutionary tools for software repair have evolved changes directly in the program code being repaired. In this work we describe an implementation: pyEDB, that encodes changes as a series of code modifications or patches. These modifications are evolved as individuals. We show pyEDB to be effective in repairing some small errors, including variable naming errors in Python programs. We also demonstrate that evolving patches rather than whole programs simplifies the removal of spurious errors.

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