LARGE-SCALE PARALLEL GRAPH-BASED SIMULATIONS - MATSim

¡
t y p e d e f map- Id , Node Nodes ;
t y p e d e f N o d e s : : i t e r a t o r N o d e s I t e r a t o r ;
Nodes nodes ;
[ . . . ]
r e a d a node i n f o r m a t i o n ;
n o d e s . i n s e r t ( m a k e p a i r ( nodeId , node ) ) ;
[ . . . ]
/ / go through a l l nodes and do something with them:
f o r ( N o d e s I t e r a t o r i t = n o d e s . b e g i n ( ) ;
i t != n o d e s . e n d ( ) ; + + i t )
Node node = i t second ;
node doSomethingWithIt ( ) ;
[ . . . ]
/ / f i n d a node by I d :
Node node = nodes [ t h e I d ] ;
Figure 3.2: The STL-map for the graph data
0 1
2 3 4 5 6
O13 O2 O48 O9 O26 O33 O14
BEFORE CALLING INSERT(3,O19)
0 1 2 3 4 5 6 7
O13 O2 O48 O19 O9 O26 O33 O14
AFTER CALLING INSERT(3,O19)
Figure 3.3: Insertion in the middle of an STL-vector. insert(position,object) is
a method defined on the STL-vector. The elements behind the insertion position are shifted
when insert command is used.
In general, the performance of the insertion into any container depends on the type of container
and where the insertion takes place. In particular, insertion at the end of an STL-vector is
very fast.
Some code elements to use an STL-vector for nodes (once more, links are analogous)
look as in Figure 3.4. The insert of the map is replaced by a push back, which means that
the new node pointer is just added at the end of the STL-vector. The iterator is essentially
the same as before, except that one does not need the second because the element that is
retrieved by it is no longer a (pointer to a) pair, but a (pointer to a) node.
An issue with an STL-vector data structure is now searching for a key, for example to
find the pointer to a node that is denoted by an ID number. A naive solution would be a linear
search, the rough code is shown in Figure 3.5.
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