You are given a network topology and routing implementation files. Please
read the README file in the program_package for more details of the 
implementation. Your task is to develop an event-driven flow level 
interconnect simulator that takes a trace file that contains a list of 
messages and outputs the messages with their communication finishing times. 
Each message contains four fields: src_id, dst_id, message_size (in bytes), 
and message starting time (in nano-seconds). The trace file has the format:

s0  d0  msize0  start_t0
s1  d1  msize1  start_t1
...
sn  dn  msizen  start_tn
-1  -1  -1  -1

In the file, the starting time is in the non-decreasing order. See sample
input file 'd1' for more details. 

The simulator will simulate the interconnect and determine the communication
finishing times for all messages, and output in a result file the messages with
their finishing times.

s0  d0  msize0  start_t0  finish_t0
s1  d1  msize1  start_t1  finish_t1
...
sn  dn  msizen  start_tn  finish_tn
-1  -1  -1  -1

See sample output file d1_3d_4_4_4_1gbps.out for example. 

For the flow rate model in this simulator, you should use the simple model 
where the flow rate is equal to the equal share of the link bandwidth for the 
most loaded link along the path. For example, assume that current there 
are three active flow f1, f2, and, f3. Flow f1 uses links l1, l2, l3, l4
all with bandwidth 1Gbps. If currently, l1 is used by 3 active flows, 
l2, l3, and l3 are used by 1 active flow. The flow rate for f1 should be 
333Mbps.

Other details in the event driven simulation can be found Lecture 16.