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, 1995Non-standard FORTRAN include files were used to pass data between routines.These include files contained the COMMON data declarations that ensured that only onedeclaration existed for each variable. Any identified utility routines kept the parameter listarguments for the passing of data. In some instances COMMON was used inappropriatelyfor passing data to utility routines. This problem was quite easy to identify because of thenecessary introduction of many simple assignment statements (putting data into theCOMMON variables) just before the utility routine call. Figure 4 demonstrates the passingof data in COMMON blocks.Data items were grouped into named COMMON blocks with related items, as theywere identified. This identification was facilitated mostly by the dimensions of the arraysand the limited amount of subroutine header information available. Tentative groupingswere made based on the declared array sizes and these were revised as actual array variableusage was identified within the source code. For example arrays with dimensions of(1..NOCELL) indicated cell properties of some sort whilst those dimensioned as(1..NOFACE) were face properties. Many of the single variables were identified as beingsuitable for COMMON by simple inspection of their usage. Switch control variables tendedto be more appropriately passed as arguments to routines. It was preferable to err on the sideof caution because of the slight potential for naming conflicts between new COMMONvariables and dummy arguments.Legacy FORTRANbecomesCALL HBOUND( H(ICELL), .. ) CALL HBOUND( ICELL, .. )SUBROUTINE HBOUND( HVAL, .. ) SUBROUTINE HBOUND( ICELL, .. )REAL HVALINCLUDE 'DATABASE.INC'HVAL = HVAL * ...INTEGER ICELLH(ICELL) = H(ICELL) * ...Figure 5 :Revised argument passing for COMMON data.Dummy argument names (within subroutines) were replaced with direct access tothe newly defined COMMON array variables. Where subroutines were receiving argumentswhich were single array elements it was necessary to ensure that the appropriate array indexwas available within the subroutine. The code fragment (Figure 5) indicates how arrayindex values were passed instead of the array elements.Stage (2):Name and algorithm clarification.FORTRAN-77 standard 6 character identifiers and routine names were replacedwith longer, lower case, names that convey functional meaning and usage. SPAG was usedto automatically rename the identifiers as it prevents and reports renaming conflicts. Someof the initial name changes are detailed in Figure 6.Appendix 11.2 Page 142-10 10