Maybe Glasgow's glasgow.support.bits should be upstreamed and used instead?

I'm not going to touch pysim until 0.1, and there's a complete rewrite planned for 0.2 that will remove the dependency on bitarray.

Note that Glasgow depends on both anyway. glasgow.support.bits is immutable.

Glasgow only uses bitarray in a few applets, so I figured it could probably be migrated away.

I already tried to do that during migration to bits. I eventually decided to keep bitarray for mutable cases, though it might be possible to use a list of chunks anyway, assuming someone benchmarks it and figures out a good chunk size.

Fair enough; but in any case, using Glasgow on PyPy is a lot more niche than using nmigen on PyPy, and it has a lot more dependencies regardless.

I thought I'd take a look at nmigen (migrating from migen), and I just ran into this issue.

❯ python .\haddecks.py --document-only
lxbuildenv: v2019.8.19.1 (run .\haddecks.py --lx-help for help)                                                                                                                                                            Traceback (most recent call last):
  File ".\haddecks.py", line 17, in <module>
    from litex.build.lattice import LatticePlatform
  File "D:\Code\had\haddecks\deps\litex\litex\__init__.py", line 4, in <module>
    from litex.soc.interconnect import packet
  File "D:\Code\had\haddecks\deps\litex\litex\soc\interconnect\packet.py", line 4, in <module>
    from nmigen.compat import *
  File "D:\Code\had\haddecks\deps\nmigen\nmigen\compat\__init__.py", line 8, in <module>
    from .sim import *
  File "D:\Code\had\haddecks\deps\nmigen\nmigen\compat\sim\__init__.py", line 5, in <module>
    from ...back.pysim import *
  File "D:\Code\had\haddecks\deps\nmigen\nmigen\back\pysim.py", line 5, in <module>
    from bitarray import bitarray
ModuleNotFoundError: No module named 'bitarray'
❯

I'm not actually using the simulator, so this dependency is definitely unfortunate.

@xobs Have you actually installed nMigen's dependencies? Because there is no goal to reduce the amount of dependencies to zero.

@whitequark I've cloned the repository next to the existing migen repository, and changed my references to point there.

I was hoping nmigen would be a drop-in replacement for migen, however the addition of an installation step means that I will stick to migen for now.

@xobs - You install migen, why wouldn't you install nmigen?

@xobs A user of nMigen is expected to be familiar with the absolute basics of Python package management. That's like saying "Yosys has dependencies, so I will stick to Vivado for now". I mean, sure, you can do that, but that's not a problem with Yosys or nMigen, it is a problem with your lack of desire to learn the fundamentals of the programming toolkit you are using.

@mithro I don't install migen, I check it out. I don't like using pip because it always breaks in spectacular ways. It's difficult to run a workshop offline, and isn't included in all of the official python installations. Running pip install has about a 50% success rate in my experience, so I very much like to avoid using it.

For example:

C:\Users\smcro>python -m pip install git+https://github.com/m-labs/nmigen.git
Collecting git+https://github.com/m-labs/nmigen.git
  Cloning https://github.com/m-labs/nmigen.git to c:\users\smcro\appdata\local\temp\pip-y_btvmjq-build
Unknown requires Python '~=3.6' but the running Python is 3.5.2
You are using pip version 9.0.1, however version 19.2.3 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

C:\Users\smcro>

With migen I just add it to my PYTHONPATH variable and go. No need to mess with installing anything. Plus it's much easier to make contributions, since it's just in a subdirectory.

@xobs nMigen requires 3.6 and above, though I'm acutely aware that upgrading Python and pip3 on Windoze can be a painful process.

@xobs In your example pip correctly tells you that nMigen requires Python 3.6, which is written in its README file:

nMigen is designed for Python 3.6 and newer. nMigen's Verilog backend requires Yosys 0.9 or a newer version.

I also have the official 3.7.3 installed:

C:\Users\smcro>python --version
Python 3.7.3

C:\Users\smcro>python -m ensurepip --default-pip
D:\Software\ecp5-toolchain-windows-v1.5\bin\python.exe: No module named ensurepip

C:\Users\smcro>python -m pip install git+https://github.com/m-labs/nmigen.git
D:\Software\ecp5-toolchain-windows-v1.5\bin\python.exe: No module named pip

C:\Users\smcro>

OK, so what you're actually asking for is reliable installation instructions for Windows. I agree that this is something that is currently not provided but should be (especially given that you will also need Yosys to do anything).

I also have the official 3.7.3 installed:

C:\Users\smcro>python --version
Python 3.7.3

C:\Users\smcro>python -m ensurepip --default-pip
D:\Software\ecp5-toolchain-windows-v1.5\bin\python.exe: No module named ensurepip

C:\Users\smcro>python -m pip install git+https://github.com/m-labs/nmigen.git
D:\Software\ecp5-toolchain-windows-v1.5\bin\python.exe: No module named pip

C:\Users\smcro>

Since 3.3 Python has venv module which allows one to have different application-specific package installs.

maybe the windows installation issue should be in a separate issue

@xobs I've opened #244 to track the Windows installation problems.

Just FYI - I've worked with @xobs a bit to give him some more Python background knowledge and some probably terrible advice ;-)

@xobs FYI as of today, nMigen master is pure Python. You only need to install pyvcd and only if you use the simulator. (Actually, it could probably be made an optional dependency even for that case, though the utility of a simulator that can't write waveforms is marginal.)

@xobs I apologize for being dismissive earlier. I now have a better understanding of the reasons someone would want to put packages on PYTHONPATH or copy them into site-packages directly without using pip. Although not a recommended way to use nMigen, I've made sure that the next release will support it properly, and I'll keep that working for foreseeable future. I also wrote detailed installation instructions for installing my fork, including for Windows: https://nmigen.info/nmigen/latest/install.html.

Please let me know if these changes work for you.

@whitequark Thank you for the changes. I will take another look at nmigen. The approach is really exciting, so I'm looking forward to being able to try it out.