On Wed, 28 Oct 2009, James wrote:
Jeremiah Willcock wrote:
On Wed, 28 Oct 2009, James wrote:
Jeremiah Willcock wrote:
You could also just declare the graph in whichever scope will end up storing it and then pass it by reference to the construction function:
void function(Graph& g) { // build g, or build a temporary and assign it to g }
Graph the_graph; function(the_graph);
Where are you going to be putting the final graph? Will it be in a variable in your main(), even if it is not constructed there?
-- Jeremiah Willcock Jeremiah,
I'm sorry if I was not clear in my first post. The majority of the code (along with the main routine) is written in Fortran. I am using the graph to update a number of arrays which are needed for this Fortran code. I will create the graph in a subroutine (or c++ function) and modify it in another c++ function. The graph is not called in the main routine, only in subroutines.
I need to know the way the graph is stored so I can pass it back to the main function (or perhaps define it as a public variable).
In reference to the code snippet above, am I correct in reading it as the creating routine will be defined as: void function(Graph& g) { // build g, or build a temporary and assign it to g } and then the function to modify it would be defined as: void modify_the_graph(Graph& g){ \\ some graph manipulations here }
Where is the variable holding the graph going to be? If it doesn't have a Fortran type the variable cannot be in Fortran code. Are you going to have a global variable (in C++) that contains the graph? Otherwise, you might need to use a raw (not shared) pointer to the graph, managing the memory yourself, and pass it between Fortran and C++ as either some kind of interoperability C pointer type (in newer Fortran versions), a large enough integer, or maybe a Cray pointer.
-- Jeremiah Willcock
That is the issue. I agree that to manipulate the graph in the Fortran portion of the code would be difficult (due the lack of a comparable data type). Luckily, I don't need to modify the graph in the Fortran portion of the code, I just need to allow for a c++ function to access the graph. If I can define the graph as a global variable in c++ and negate the need to pass the graph from the create_graph function to the modify_graph function via the Fortran main routine: Create_Graph.cpp -> Main.f -> Modify_Graph.cpp would be great.
Would I accomplish this as: in create_graph.cpp Graph& g;
void create_graph(){ \\ create graph }
and in modify_graph.cpp extern Graph& g;
void modify_graph(){ \\... }
The storage for the graph needs to be somewhere; making the variables of type Graph rather than Graph& would solve that problem. -- Jeremiah Willcock