import numpy as np
import threading
import multiprocessing
import gc
import time
import sys
from time_measurement import time_measurement_longest, longest_time_accumulator, tests_time
import linear_algebra_utils as linAlg


@time_measurement_longest(longest_time_accumulator)
def RichardsonThread(A, b, x, _x, omega, start, end):
    for i in range(start, end):
        sigma = np.dot(A[i, :], _x) - A[i, i] * _x[i]
        x[i] = (1 - omega) * _x[i] + omega * (b[i] - sigma) / A[i, i]

def RichardsonMethodThreads(A, b, lambda_min, lambda_max, max_iterations, x0=None, tol=1e-5):
    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 = i * chunk_size # start jest indeksem w A. Wątki otrzymują kolejny punkt startowy będący wielokrotnością rozmiaru porcji na wątek
            end = n if i == num_threads - 1 else (i + 1) * chunk_size
            thread = threading.Thread(target=RichardsonThread, args=(A, b, x, _x, omega, start, end))
            threads.append(thread)
            thread.start()
        
        for thread in threads:
            thread.join()
        
        # Ax = linAlg.SequentialLinearAlgebraUtils.matrix_vector_multiply(A, x)
        # residual = linAlg.SequentialLinearAlgebraUtils.vector_vector_subtraction(b, Ax)
        # if (linAlg.SequentialLinearAlgebraUtils.vector_norm(residual) < tol):
        #         break

    end_time = time.perf_counter()
    gc.enable()
    total_time = end_time - start_time
    sequential_time = total_time - longest_time_accumulator.total_time
    
    print(f"Total: {total_time:.3e}s, Seq: {sequential_time:.3e}s, Parallel (threads): {longest_time_accumulator.total_time:.3e}s, Tests time: {tests_time.total_time:.3e}s")
    
    return x, 0