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Seting Probe Parameters
 

 

Probe tools are used to setup statistic variables interested you. Although a simulation model may write values during the simulation for each variable, these values are not shown in the Analysis tool unless a corresponding probe has been defined.  When you click the  button, an empty probe window will pop up in the workspace. You can either add new probe items or click  to open an existing probe file. After you open our probe file for the DebugModel (named ProbeFile), the workspace will look like this. All existing probe items are displayed in the Probe Workspace at the upper part, network structure is shown in the Network Subwindow and node hierarchy is shown in the Node Subwindow at the lower part.  There are eight types of probes, but we only use the Node Statistic Probe in our model. This type of probe is used for recording  dynamic collections of numeric measurements of a particular node. you can click  to add a new Node Statistic Probe.

 

Right-click a probe in the Probe Workspace to configure its attributes. You can setup the name of the probe, its subnet number, node number, process name and the statistic index you specified in the source code. The lower part network structure and node hierarchy can help you setup these fields. In our models, all probes' "vector data" were enabled. Vector data is a series of entries, where each entry is a time-value pair. This representation shows you how a statistic of interest varies over time. The "vector start" and "vector stop" define the simulation time interval to collect the vector data. By default, the interval corresponds to the entire simulation.

 

In addition to setup the probes in the probe tool, you should write a block of code in the source file, to write the values of probes and corresponding simulation time to the probe file (extension .ov). This operation can be fulfilled by calling op_stat_local_write function, which is provided by OPNET standard function library. Here is an example:

    #define Node_RSVP_AVG_DELAY 3             // Index of statistic probe

float Node_RSVP_Delay = 0;                // Initial probe
float Node_RSVP_Pkts = 0;
.
.
if ( Got a RSVP packet )
    {
    Node_RSVP_Delay += delay;             // Update probe
    Node_RSVP_Pkts ++;
    op_stat_local_write( Node_RSVP_AVG_DELAY, Node_RSVP_Delay / Node_RSVP_Pkts );
                                           // Write value-time pair to the file.
    }
.
.
Click  to save your work. Run your simulation by typing
op_runsim -net_name DebugModel -ef DebugModel

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