PhD Thesis - staffweb - University of Greenwich

APPENDIX 2 : Journal Paper "Case Study : An Incremental Approach to Re-Engineeringa Legacy FORTRAN C.F.D. Code in C++", Ewer J., Knight B. and Cowell D.,Advances in Engineering Software, Vol. 22, pp 153-168, 1995Enhanced debug facilities for code development via class methodsfloat & Cell_Class::access( int mode, int var ){#ifdef __DEBUG_CODE__if ( ( mode == NEWEST ) && ( var == TEMPERATURE ) ) {if ( data[mode][var] < 0.0 ){// Error negative temperature detected in cell data access}}#endif}return data[ mode ][ var ];Figure 13 :New data access function.The solvers available in CWNN were all based on whole matrix solving techniques.It was suggested, by a CFD researcher, that a true cell -by-cell solver should be developed.This has been implemented from some of the software components produced during thisproject.The implementation of a vector class for normal and displacement vectors hasgreatly simplified the source code. The original FORTRAN code had to loop over all threedimensions for calculations whereas now, simple vector algebra can be performed. Operatoroverloading has been used to give the vector algebra a more natural syntax, as found in mostreference texts. Figure 14 shows the equivalent loops for calculating the cell centres fromthe legacy code and the re-engineered code, which uses vector methods. Such instanceswere relatively easy to find because the loop dimensions go from 1 to 3 (or 1 toDIMENSIONS). It was possible to abstract one and sometimes two levels of loopingbecause of the new operators and functions provided for vector algebra in the vector class.These functions included dot- and cross- product utilities.Original legacy code New C++ code using a vector classDO 1 I = 1, NOCELL int i, j;DO 2 J = 1, 3 for ( i=1; i