Tracing garbage collection
（重定向自Mark and sweep）
![Naive mark-and-sweep in action on a heap containing eight objects. Arrows represent object references. Circles represent the objects themselves. Objects #1, #2, #3, #4, and #6 are strongly referenced from the root set. On the other hand, objects #5, #7, and #8 are not strongly referenced either directly or indirectly from the root set; therefore, they are garbage.](/Images/godic/202501/26/Animation_of_the_Naive_Mark_and_Sweep_Garbage_Collector_Algorithm1925.gif")
![An example of tri-color marking on a heap with 8 objects.
White, grey, and black objects are represented by light-grey, yellow, and blue, respectively.](/Images/godic/202501/26/Animation_of_tri-color_garbage_collection1925.gif")
In computer programming, tracing garbage collection is a form of automatic memory management that consists of determining which objects should be deallocated ("garbage collected") by tracing which objects are reachable by a chain of references from certain "root" objects, and considering the rest as "garbage" and collecting them. Tracing garbage collection is the most common type of garbage collection – so much so that "garbage collection" often refers to tracing garbage collection, rather than other methods such as reference counting – and there are a large number of algorithms used in implementation.