Various improvements suggestions

[mciepluc]

I do have a little bit feedback.

Coverage

• Explicitly named bins would ease reading of the coverage report.

  coverage.CoverPoint("transaction.payload_length",
                                   ...
                                  bins = [('runt', (0, 64)), ('normal', (65, 1500)), ('giant', (1501, 10000))]),
                                  ...

• Promote coverage_db to a true singleton object with various query and reporting methods. Arguments include filtering by bin or transaction name, amount of detail, etc. Also a custom accessor to get and inspect a particular CoverItem. This could allow feedback to CRV to achieve faster functional coverage during runtime.

  coverage_db = cocotb.coverage.get_coverage_database()
  coverage_db.report_covered(**kwargs)
  coverage_db.report_uncovered(**kwargs)
  coverage_db.get_coverage_for_item(item_name)
  # etc.

CRV

• A standardized method to build random lists, such as for packet payloads. Would take parameters for min/max len() and min/max values that applies to all values in the list. I realize the underlying constraint.py doesn't support this. Maybe just implement using random module and generate during pre_randomize() or post_randomize()? Other constraints could then use len(txn.payload) in the constraint solver.

I hacked together something like this in my base transaction class:

from random import choice
from cocotb.crv import Randomized

class MyRandomized(Randomized):
    def __init__(self):
        super().__init__()
        self._rand_lists = {}

    def add_rand_list(self, name, lengths, values, pre_randomize=True):
        self._rand_lists[name] = (lengths, values, pre_randomize)
        setattr(self, name, [])

    def build_rand_lists(self, pre_randomize):
        for name, (lengths, values, pr) in self._rand_lists.items():
            if pre_randomize == pr:
                setattr(self, name, [choice(values) for x in range(choice(lengths))])

    def pre_randomize(self):
        self.build_rand_lists(pre_randomize=True)

    def post_randomize(self):
        self.build_rand_lists(pre_randomize=False)

• A small bit of style advice. Use CamelCase for class names but all_lower_case() for methods. E.g., addRand() --> add_rand()

Keep up the good work!

Originally posted by @jrpetrus in https://github.com/potentialventures/cocotb/pull/490#issuecomment-358652919

[mciepluc]

Most of the suggested enhancements have been added. Regarding building random dataset options, I don't see a need to do this, as there are different ways, depending on particular requirements.