Allocation_Dev[i][j] += Need_Dev[i][j];这段代码是什么意思

这段代码是将一个二维数组 `Need_Dev` 的值加到另一个二维数组 `Allocation_Dev` 的对应位置上。具体来说，这个代码是在处理操作系统中的进程资源分配问题中的一部分。其中，`Need_Dev` 代表了每个进程对每种资源的需求量，而 `Allocation_Dev` 则代表了每个进程已经被分配到的资源量。这段代码的作用就是将某个进程的未满足资源需求加到已分配的资源上。

相关问题

使用首次适应算法改写class MemoryManager: def __init__(self, allocator): self.allocator = allocator def allocate(self, process, request_size): memory_view = self.allocator.memory_view() '''这里是写的''' # Find the best fit block for the process best_fit_block = None best_fit_size = float('inf') for i in range(len(memory_view)): if memory_view[i] is None: # Check if the block is free block_size = 0 j = i while j < len(memory_view) and memory_view[j] is None: block_size += 1 j += 1 if block_size >= request_size and block_size < best_fit_size: best_fit_block = i best_fit_size = block_size if best_fit_block is not None: # Allocate memory for the process block_start = best_fit_block self.allocator.allocate_memory(block_start, request_size, process) else: # No suitable block found, allocation failed raise AssertionError('allocation failed')

可以将首次适应算法改写成以下代码：

class MemoryManager:
    def __init__(self, allocator):
        self.allocator = allocator
        self.last_allocated = 0

    def allocate(self, process, request_size):
        memory_view = self.allocator.memory_view()
        # Find the best fit block for the process
        best_fit_block = None
        best_fit_size = float('inf')
        i = self.last_allocated
        while i < len(memory_view):
            if memory_view[i] is None:  # Check if the block is free
                block_size = 0
                j = i
                while j < len(memory_view) and memory_view[j] is None:
                    block_size += 1
                    j += 1
                if block_size >= request_size and block_size < best_fit_size:
                    best_fit_block = i
                    best_fit_size = block_size
            i += 1

        # If no block is found from last allocated position to end then search from beginning
        if best_fit_block is None:
            i = 0
            while i < self.last_allocated:
                if memory_view[i] is None:  # Check if the block is free
                    block_size = 0
                    j = i
                    while j < len(memory_view) and memory_view[j] is None:
                        block_size += 1
                        j += 1
                    if block_size >= request_size and block_size < best_fit_size:
                        best_fit_block = i
                        best_fit_size = block_size
                i += 1

        if best_fit_block is not None:
            # Allocate memory for the process
            block_start = best_fit_block
            self.allocator.allocate_memory(block_start, request_size, process)
            self.last_allocated = block_start + request_size
        else:
            # No suitable block found, allocation failed
            raise AssertionError('allocation failed')

这里的改动在于在 `allocate` 方法中加入了 `self.last_allocated` 变量，它表示上一次分配内存时的位置，从这个位置开始向后搜索空闲块，避免在整个内存中搜索。如果在搜索到结尾仍然没有找到适合的块，则从头开始搜索。

用循环首次适应算法改写代码class MemoryManager: def init(self, allocator): self.allocator = allocator def allocate(self, process, request_size): memory_view = self.allocator.memory_view() best_fit_block = None best_fit_size = float('inf') for i in range(len(memory_view)): if memory_view[i] is None: block_size = 0 j = i while j < len(memory_view) and memory_view[j] is None: block_size += 1 j += 1 if block_size >= request_size and block_size < best_fit_size: best_fit_block = i best_fit_size = block_size if best_fit_block is not None: block_start = best_fit_block self.allocator.allocate_memory(block_start, request_size, process) else: raise AssertionError('allocation failed')

以下是使用循环首次适应算法改写的代码：

class MemoryManager:
    def __init__(self, allocator):
        self.allocator = allocator
    
    def allocate(self, process, request_size):
        memory_view = self.allocator.memory_view()
        block_start = None
        block_size = 0
        for i in range(len(memory_view)):
            if memory_view[i] is None:
                if block_start is None:
                    block_start = i
                block_size += 1
                if block_size == request_size:
                    self.allocator.allocate_memory(block_start, request_size, process)
                    return
            else:
                block_start = None
                block_size = 0
        
        raise AssertionError('allocation failed')

这个类只有一个方法`allocate`，使用循环首次适应算法分配内存块。如果成功分配，则调用`self.allocator.allocate_memory`将分配的内存块信息传递给分配器。如果分配失败，则触发异常。