Users' questions

What is a reference counted object?

What is a reference counted object?

In computer science, reference counting is a programming technique of storing the number of references, pointers, or handles to a resource, such as an object, a block of memory, disk space, and others. In garbage collection algorithms, reference counts may be used to deallocate objects that are no longer needed.

Does Ruby use reference counting?

Ruby uses John McCarthy’s original mark and sweep algorithm, while Python uses reference counting. But when we look more closely, we see that Python uses bits of the mark and sweep idea to handle cyclic references, and that both Ruby and Python use generational garbage collection in similar ways.

Is reference counting garbage collection?

Automatic Reference Counting is technically a form of garbage collection. However, typically when one refers to a garbage collector, they mean a separate process or subsystem that runs in the background independent of your application.

What is reference counting in C?

Reference counting is one such technique. This method is simply keeping an extra counter along with each object that is created. The counter is the number of references that exist to the object, in the C/C++ case this would how many pointers refer to this object.

What is the reference count of an unreachable object?

Even if A and B become unreachable from the rest of the object graph, their reference count will never reach zero. That’s because they still hold a reference to each other.

What is reference counting in Java?

Reference counting collectors keep track of how many references are pointing to each Java object. Once the count for an object becomes zero, the memory can be immediately reclaimed. This immediate access to reclaimed memory is the major advantage of the reference-counting approach to garbage collection.

Is Ruby garbage collected?

Ruby, like most other modern, high-level programming languages, doesn’t force you to manage memory. This feature is called garbage collection, or GC, and you get it for free in Ruby.

Can I pass by reference in Ruby?

When someone asks whether a language is “pass-by-reference” they usually want to know when you pass something to a function and the function modifies it, will it be modified outside the function. For Ruby the answer is ‘yes’.

Is reference counting faster than garbage collection?

Tracing GC is not always faster. GC time is proportional to the size of the allocated memory, reference counting time is not. Reference counting time is proportional to data structure sizes on deletion.

What is a strong reference cycle?

A strong reference cycle happens when 2 instances keep a strong reference to each other. You can accidentally create such a cyclic reference, for example when working with 2-way “links” between objects, or with closures.

What is the use of phantom reference in Java?

PhantomReference: Phantom reference objects are enqueued after the collector determines that their referents may otherwise be reclaimed. Phantom references are most often used for scheduling pre-mortem cleanup actions in a more flexible way than is possible with the Java finalization mechanism.

What are weak references in Java?

A weak reference, simply put, is a reference that isn’t strong enough to force an object to remain in memory. Weak references allow you to leverage the garbage collector’s ability to determine reachability for you, so you don’t have to do it yourself.

When do we say the object is in motion?

An object is moving if its position relative to a fixed point is changing. Even things that appear to be at rest move. When we describe the motion of one object with respect to another, we say that the object is moving relative to the other object.

How are objects in motion relative to each other?

Motion is a relative concept, so you are never “moving” but only “moving with respect to something”. But in the case of the two objects, both were moving across time to a certain degree, but they viewed each others motion across time as being at different magnitudes of motion.

Which is the reference frame for relative motion?

If you say a person is sitting in a train moving at 10 m/s east, then you imply the person on the train is moving relative to the surface of Earth at this velocity, and Earth is the reference frame.

How to analyze relative motion in one and two dimensions?

Explain the concept of reference frames. Write the position and velocity vector equations for relative motion. Draw the position and velocity vectors for relative motion. Analyze one-dimensional and two-dimensional relative motion problems using the position and velocity vector equations. Motion does not happen in isolation.