Generate the single router design

[김지현]

Hello,

I am new to PyMTL and I'm interested in utilizing PyMTL3 or PyMTL3-net for my research.

To be more specific, my goal is to create a Verilog model of a single router using PyMTL3(-net), and later, evaluate the area and timing overhead using a synthesis tool.

While I've managed to modify the router design in PyMTL3-net, I found that synthesizing the entire network (such as mesh or ring) is unnecessary for my research; all I require is a model of a single router. Thus, I have two questions:

1. 1. Is it possible to generate a Verilog model of a single router design using PyMTL3-net (or PyOCN)?

   
   

2. 2. If this isn't possible, would it be more practical (or advisable) to create the router design using PyMTL3?

Thank you in advance!

[Yanghui Ou]

Hi,

Thank you for using pymtl3-net. Yes it is definitely possible to just generate Verilog for a router. You can simply run a router test with `--test-verilog` flag using pytest. Alternatively, you can also write a simple test for your router like this to generate the verilog:

from pymtl3.stdlib.test_utils import (run_sim,
                                      config_model_with_cmdline_opts)

def test_translate( cmdline_opts ):
  dut = MyRouter()
  dut = config_model_with_cmdline_opts( dut, cmdline_opts, duts=[] )

Then you can run this test using pytest with the `--test-verilog` flag. 

Let me know if you run into any problems.

Best,

Yanghui

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[Jihyun Kim]

First of all, thanks for your response!

I actually wanted to use the router code from /pymtl3-net/router directly, perhaps configure a network that has only one router.
Maybe is this possible in pymtl3-net?

If I can't do that in pymtl3-net, I am considering using the module/class that is already in pymtl3-net, SwitchUnitRTL.py, XYZRouteUnitRTL.py, etc.
Would this approach be feasible, or should I considering made my own router from scratch?

If you could confirm my understanding or provide any additional insights, I would greatly appreciate it.

Best,
Jihyun

[Yanghui Ou]

Hi Jihyun,

You can use the router code directly. You just need to pick the corresponding router test and run it with the `--test-verilog` flag. You can also use the `-k` command to select the test you want to run. For example, you can run the following commands to generate the router for mesh network:

$ cd pymtl3_net/meshnet/test
$ mkdir build && cd build
$ pytest ../MeshRouteUnitRTLMflitXY_test.py --test-verilog -k test_1pkt

If you want to generate Verilog code for your own router or with your customized parameters, you can add an additional test case that looks like this:

from pymtl3.stdlib.test_utils import (run_sim,
                                      config_model_with_cmdline_opts)

def test_translate( cmdline_opts ):
  dut = MyRouter()
  dut = config_model_with_cmdline_opts( dut, cmdline_opts, duts=[] )

Where `MyRouter` is your customized router class.

Let me know if this answers your question.

Best,

Yanghui

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[Jihyun Kim]

Yes, it is the answer that I want.

I am sorry but I still have some concerns regarding the output of the test.

I have been experimenting with generating the router code in pymtl3-net using the command sequence detailed below:

$ cd pymtl3_net/meshnet/test
$ mkdir build && cd build

$ pytest ../MeshRouterRTL_test.py --test-verilog
The output seems to indicate that the pytest did not complete successfully:
================================================================== test session starts ==================================================================
platform linux -- Python 3.7.5, pytest-7.4.0, pluggy-1.2.0
rootdir: /root/cornell-brg/cornell-brg/posh-ocn
configfile: pytest.ini
plugins: pymtl3-3.1.15, hypothesis-6.79.4
collected 5 items                                                                                                                                       

../MeshRouterRTL_test.py FFFFF         

Furthermore, it output the MeshRouterRTL__1c0c758909513a6e__pickled.v and MeshRouterRTL__d7ef04b1c70dfb50__pickled.v.
While there is some output, I am not sure whether these files are considered valid outputs.

Earlier, I had also looked into a GitHub issue (https://github.com/cornell-brg/pymtl3-net/issues/24) to generate the verilog file: 
With this command, most of the testcase also siently fails, but some verilog files are still generated. 
$ pytest ../ -v --test-verilog
But running pymtl3-net from the script directory with this command generate the mesh.v that seems normal. 
$ pymtl3-net gen mesh --ncols 4 --nrows 4

In summary, I want to double check the generated file like XX__pickled.v. is still valid, or maybe there might be something wrong with my environment setting. 

Thanks again, 
Jihyun

[Christopher Batten]

Hmmm ... what is the error you are seeing? you might need to use something like --tb=short so that pytest tells you more information about the error ...

Have you installed Verilator 4.036? There are instructions here on how to do that:

https://github.com/pymtl/pymtl3

If everything it setup correctly when you run --test-verilog it generates the Verilog, uses Verilator to translate the Verilog into C++, then automatically generates appropriate wrappers, compiles the C++, and then rerun all of the tests ... so that is how you know the Verilog is correct ...

Hope this helps!

Chris

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[Jihyun Kim]

Thanks for your reply!

Yes, the problem is solved now. 

I checked the error messeage with  --tb=short flag, and it shows: 

/root/venv/lib/python3.8/site-packages/pymtl3/passes/backends/verilog/import_/VerilogVerilatorImportConfigs.py:366: in _get_all_includes
    subprocess.check_output(get_dir_cmd, stderr = subprocess.STDOUT).strip()
/usr/lib/python3.8/subprocess.py:415: in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
/usr/lib/python3.8/subprocess.py:493: in run
    with Popen(*popenargs, **kwargs) as process:
/usr/lib/python3.8/subprocess.py:858: in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
/usr/lib/python3.8/subprocess.py:1704: in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
E   FileNotFoundError: [Errno 2] No such file or directory: 'pkg-config'

So I install the pkg-config, and  all the tests are now passing without any issues.

Thank you once again for your help and the amazing work!

Best, 

Jihyun

[Christopher Batten]

Glad to hear it is working!

-c

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