WUT_Computer_Science/Programming/PORR/code/threads_too_simple.py
Krzysztof kuhy Rudnicki faef20dc45 PORR: zero findings, 18 tests still passing after every refactor
598 findings to none, and the suite ran through `./run.sh run` after each step
rather than at the end -- 18 passed, 27s, every time.

The shape of this one was different from the other courses. PORR is four
implementations of the same linear algebra (sequential, threads, processes,
dask), so nearly every finding came in groups of four:

- 229 missing annotations. Rather than `object`, which mypy strict rejects on
  every attribute access, each module declares what these actually are:
  `Matrix = np.ndarray | list[list[float]]` and the vector equivalent. The
  backends really are called with both -- comparing them is the point of the
  course.
- 76 names: `A` -> matrix, `Ab` -> augmented, `Ax` -> product, `I` ->
  identity, `dA` -> dask_matrix, and the two CamelCase functions. Renamed
  through `tokenize`, not regex, so no string or comment was touched.
- 121 missing docstrings, one per method name since the names repeat across
  all four backends.
- Seven functions over the argument limit, all taking the same seven or nine
  loose values. They are two frozen dataclasses now, in a new
  richardson_problem.py: `Problem(matrix, rhs, lambda_min, lambda_max)` and
  `Settings(max_iterations, x0, tol)`. `RichardsonMethod.__init__` also took a
  `size` argument it never read.
- threads_indep_old's iteration did "split into chunks, submit, wait" four
  times by hand (C901 11, PLR0915 54). One `_run_chunked` helper.
- tests.py's two bare asserts became explicit raises, per the no-ignores rule.
  `assert False` was also B011: `python -O` deletes it, so the non-convergence
  branch would have silently passed under optimisation.

Real fixes rather than style: np.random -> Generator, `os.path.exists` ->
Path, an `except Exception` around dask narrowed to the errors it actually
raises, and two runnable modules that logged at INFO without ever calling
basicConfig -- caught by scripts/check_refactor_safety.py, which is now doing
the job it was written for.

Repo-wide: 1,781 findings -> 1,183, all of them in the five courses left.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0172dj34FDpao6wsix8ZuCzE
2026-08-28 21:01:13 +02:00

100 lines
2.8 KiB
Python
Executable File

#!/usr/bin/env python3
"""Threaded Richardson, the first attempt (one thread per slice)."""
import gc
import logging
import multiprocessing
import sys
import threading
import time
import numpy as np
from richardson_problem import Problem, Settings
from time_measurement import (
longest_time_accumulator,
tests_time,
time_measurement_longest,
)
logger = logging.getLogger(__name__)
# Called with numpy arrays here and with plain lists in the sequential
# backend; the aliases name both.
Matrix = np.ndarray | list[list[float]]
Vector = np.ndarray | list[float]
@time_measurement_longest(longest_time_accumulator)
def richardson_thread(
matrix: Matrix,
b: Vector,
vectors: tuple[Vector, Vector],
omega: float,
span: tuple[int, int],
) -> None:
"""Run one thread's slice of a Richardson iteration.
``vectors`` is (x, next_x) and ``span`` is the half-open row range this
thread owns.
"""
x, _x = vectors
start, end = span
for i in range(start, end):
sigma = np.dot(matrix[i, :], _x) - matrix[i, i] * _x[i]
x[i] = (1 - omega) * _x[i] + omega * (b[i] - sigma) / matrix[i, i]
def richardson_method_threads(
problem: Problem, settings: Settings
) -> tuple[Vector, str | None]:
"""Run Richardson with one thread per chunk."""
matrix = problem.matrix
b = problem.rhs
max_iterations = settings.max_iterations
x0 = settings.x0
longest_time_accumulator.total_time = 0
longest_time_accumulator.start = sys.float_info.max
longest_time_accumulator.end = 0
gc.disable()
start_time = time.perf_counter()
n = len(b)
x0 = x0 if x0 is not None else [0.0] * len(b)
x = x0[:]
omega = 0.05 # 2 / (lambda_min + lambda_max)
num_threads = multiprocessing.cpu_count()
threads = []
chunk_size = n // num_threads
max_iterations = 1000
for _ in range(max_iterations):
_x = x[:]
for i in range(num_threads):
# start is an index into A: each thread gets the next multiple of
# the per-thread chunk size as its starting point.
start = i * chunk_size
end = n if i == num_threads - 1 else (i + 1) * chunk_size
thread = threading.Thread(
target=richardson_thread, args=(matrix, b, (x, _x), omega, (start, end))
)
threads.append(thread)
thread.start()
for thread in threads:
thread.join()
end_time = time.perf_counter()
gc.enable()
total_time = end_time - start_time
sequential_time = total_time - longest_time_accumulator.total_time
logger.info(
"Total: %ss, Seq: %ss, Parallel (threads): %ss, Tests time: %ss",
total_time,
sequential_time,
longest_time_accumulator.total_time,
tests_time.total_time,
)
return x, 0