source: vis_dev/vis-2.3/share/help/restruct_fsmCmd.txt @ 60

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2  restruct_fsm - Restructre the STG of a finite state machine to reduce power
3  dissipation.
4     _________________________________________________________________
5
6   restruct_fsm [-D <fileHead>] [-d <divMethod>] [-E] [-F <factMethod>] [-f
7   <probFile>] [-h] [-N] [-o <orderFile>] [-p <string>] [-s <restrMethod>] [-t
8   <seconds>] [-v]
9
10   This command implements an STG restructuring algorithm that exploits the
11   existence  of  equivalent  states  to  decrease power dissipation, not
12   necessarily  by  collapsing the equivalence states, but by redirecting
13   transitions in the state transition graph (STG). This algorithm is based on
14   monolithic transition relation. The complexity of the algorithm in general
15   increases with an increase in the size of the STG. The number of states and
16   edges  in the STG are exponential in the number of state variables and
17   primary inputs. The memory utilization is not necessarily exponential due to
18   symbolic  representation of the STG. For more details see, "A Symbolic
19   Algorithm for Low-Power Sequential Synthesis", ISLPED 97. This command works
20   only if VIS is compiled with CUDD package. The algorithm can handle circuits
21   described in both BLIF and BLIF-MV format. However, multi-valued variables
22   are  not  supported.  Also,  the  final  synthesized  circuit (network
23   implementation of the restructured STG) is available only in BLIF format.
24   The sequential circuit should have a single initial state. A network should
25   have been created for the circuit and its primary inputs and state variables
26   assigned BDD ids prior to the invocation of this command. A network can be
27   created by the command flatten_hierarchy and command static_order assigns
28   BDD ids to the input and state variables. The command proceeds by creating
29   BDDs for the outputs and next state functions. An FSM data structure is then
30   created on which subsequent operations are performed. After the STG is
31   restructured a new circuit is synthesized by symbolic factorization based on
32   Zero-Suppressed Decision Diagrams (ZDDs). The final synthesized circuit is a
33   file in BLIF format with ".ml.blif" as the extension.
34
35   The typical command flow in vis is the following:
36   vis> read_blif foo.blif
37   vis> flatten_hierarchy
38   vis> static_order
39   vis> dynamic_var_ordering -e sift
40   vis> restruct_fsm
41
42   In the above case example, the final synthesized circuit is MODEL.ml.blif if
43   the name of the design in foo.blif is MODEL.
44   Command options:
45
46   -A
47          Allow realignment (during symbolic factorization) of ZDDs after BDD
48          reordering and vice versa. This option is effective when only one of
49          the BDD or ZDD variable reordering is enabled.
50
51   -D <fileHead>
52          Specify the output file name for synthesized circuit. File extension
53          is not necessary. By default, the model name of the circuit is used.
54          For example, -D foobar, will result in foobar.ml.blif
55
56   -d <divMethod>
57          Choose a divisor. See synthesize_network for more details.
58
59   -E
60          Print the number of equivalence classes in the FSM.
61
62   -F <probFile>
63          File with primary input probabilities, one per line. input_name
64          <probability>
65
66   -f <factMethod>
67          Choose a method for factorization. See synthesize_network for more
68          details.
69
70   -h
71          Print command usage.
72
73   -i <string>
74          Specify the prefix to be used to generate names for internal nodes
75          during synthesis. By default, the prefix is "_n".
76
77   -N
78          Expand  the  reachable  set R to include those states which are
79          equivalent to R but not reachable. The default is not to include such
80          states.
81
82   -o <orderFile>
83          File to output BDD variable ordering after the restructured circuit
84          is synthesized.
85
86   -R <value>
87          Allow  reordering  in  BDD and/or ZDD variables during symbolic
88          factorization stage.
89
90          0 : (default) No reordering neither in BDD nor in ZDD.
91
92          1 : Allows reordering only in BDD, not in ZDD.
93
94          2 : Allows reordering only in ZDD, not in BDD.
95
96          3 : Allows reordering both in BDD and in ZDD.
97
98   -s <heuristic>
99          Heuristic to perform restructuring. Consider a fragment of an STG
100          containing states A,B and C and an edge from A to B. Let B and C be
101          equivalent. Since B and C are equivalent, it is possible to change
102          the transition between A and B to A and C. In the more general case,
103          the choice can be driven by different cost constraints. The following
104          are the heuristics:
105          ham  : Hamming distance based heuristic. An edge is chosen that
106          reduces the Hamming distance (or state bit transitions) between the
107          states.
108          fanin  :  Fanin  oriented  heuristic. A representative from the
109          equivalence class is chosen that reduces the total average state bit
110          switching on the incoming edges.
111          faninout : Fanin-Fanout oriented heuristic. A representative from the
112          equivalence class is chosen that reduces the total average state bit
113          switching on the incoming as well as outgoing edges.
114          cproj : A simple C-Projection. A representative from the equivalence
115          class is chosen which is closest to the initial state. The distance
116          d(x,y) is defined as:
117          sum_{i=0}^{N-1}(|x_i - y_i| cdot 2^{N-i-1}).
118
119   -T
120          Try to share more nodes during symbolic factorization. Existing
121          divisors are checked for potential reuse before extracting divisors
122          from the current boolean function.
123
124   -t <seconds>
125          Time in seconds allowed to complete the command. If the computation
126          time goes above that limit, the process is aborted. The default is no
127          limit.
128
129   -v
130          Turn on verbosity.
131
132   See also command : synthesize_network
133     _________________________________________________________________
134
135   Last updated on 20100410 00h02
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