skiplist | skiplist for golang - reference from redis zskiplist

 by   gansidui Go Version: Current License: No License

kandi X-RAY | skiplist Summary

kandi X-RAY | skiplist Summary

skiplist is a Go library. skiplist has no bugs, it has no vulnerabilities and it has low support. You can download it from GitHub.

import ( "fmt" "github.com/gansidui/skiplist" "log" ). type User struct { score float64 id string }. func (u *User) Less(other interface{}) bool { if u.score > other.(*User).score { return true } if u.score == other.(*User).score && len(u.id) > len(other.(*User).id) { return true } return false }. func main() { us := make([]*User, 7) us[0] = &User{6.6, "hi"} us[1] = &User{4.4, "hello"} us[2] = &User{2.2, "world"} us[3] = &User{3.3, "go"} us[4] = &User{1.1, "skip"} us[5] = &User{2.2, "list"} us[6] = &User{3.3, "lang"}. hi -→ 6.6 hello -→ 4.4 lang -→ 3.3 go -→ 3.3 world -→ 2.2 list -→ 2.2 skip -→ 1.1.
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            kandi-support Support

              skiplist has a low active ecosystem.
              It has 83 star(s) with 23 fork(s). There are 7 watchers for this library.
              OutlinedDot
              It had no major release in the last 6 months.
              There are 1 open issues and 0 have been closed. There are no pull requests.
              It has a neutral sentiment in the developer community.
              The latest version of skiplist is current.

            kandi-Quality Quality

              skiplist has 0 bugs and 0 code smells.

            kandi-Security Security

              skiplist has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
              skiplist code analysis shows 0 unresolved vulnerabilities.
              There are 0 security hotspots that need review.

            kandi-License License

              skiplist does not have a standard license declared.
              Check the repository for any license declaration and review the terms closely.
              OutlinedDot
              Without a license, all rights are reserved, and you cannot use the library in your applications.

            kandi-Reuse Reuse

              skiplist releases are not available. You will need to build from source code and install.
              Installation instructions are not available. Examples and code snippets are available.
              It has 463 lines of code, 29 functions and 3 files.
              It has high code complexity. Code complexity directly impacts maintainability of the code.

            Top functions reviewed by kandi - BETA

            kandi has reviewed skiplist and discovered the below as its top functions. This is intended to give you an instant insight into skiplist implemented functionality, and help decide if they suit your requirements.
            • GetRank returns the rank of v .
            • randomLevel returns a random level
            • newElement returns a new Element .
            • New returns a SkipList .
            Get all kandi verified functions for this library.

            skiplist Key Features

            No Key Features are available at this moment for skiplist.

            skiplist Examples and Code Snippets

            Return a string representation of this node .
            pythondot img1Lines of Code : 49dot img1License : Permissive (MIT License)
            copy iconCopy
            def __str__(self) -> str:
                    """
                    :return: Visual representation of SkipList
            
                    >>> skip_list = SkipList()
                    >>> print(skip_list)
                    SkipList(level=0)
                    >>> skip_list.insert("Key1", "Va  
            Insert a new node .
            pythondot img2Lines of Code : 36dot img2License : Permissive (MIT License)
            copy iconCopy
            def insert(self, key: KT, value: VT):
                    """
                    :param key: Key to insert.
                    :param value: Value associated with given key.
            
                    >>> skip_list = SkipList()
                    >>> skip_list.insert(2, "Two")
                    >>&  
            Removes the given key from the tree .
            pythondot img3Lines of Code : 25dot img3License : Permissive (MIT License)
            copy iconCopy
            def delete(self, key: KT):
                    """
                    :param key: Key to remove from list.
            
                    >>> skip_list = SkipList()
                    >>> skip_list.insert(2, "Two")
                    >>> skip_list.insert(1, "One")
                    >>> skip  

            Community Discussions

            QUESTION

            Which C++ random number distribution to use for the Java skip list generator?
            Asked 2022-Mar-04 at 11:08

            The Java ConcurrentSkipListMap class contains a method randomLevel that outputs the following, according to The Art of Multiprocessor Programming:

            The randomLevel() method is designed based on empirical measurements to maintain the skiplist property. For example, in the java.util.concurrent package, for a maximal SkipList level of 31, randomLevel() returns 0 with probability 3/4, i with probability 2^(−(i+2)) for i ∈ [1, 30], and 31 with probability 2^−32.

            This looks like a geometric distribution, but not quite. Is there some way to neatly define this in terms of the provided random distributions, or do I have to do my own manipulation, as such:

            ...

            ANSWER

            Answered 2022-Mar-04 at 11:08

            This looks like a geometric distribution, but not quite.

            You are right, but problem is only probability of 0. Note that you can use std::geometric_distribution, by merging first two values into one.

            Source https://stackoverflow.com/questions/71349963

            QUESTION

            Why does this JavaScript SkipList implementation have "nodes" and "groups" which are structured the way they are?
            Asked 2022-Feb-25 at 14:17

            A SkipList is a probabilistic data structure used, at least in part, for implementing an ordered key/value map. It is arranged in levels where higher levels skip nodes (the higher up, the more it skips), and the lowest level contains the nodes. As far as I have read, each level is implemented as a linked list, possibly a doubly linked list. And for some reason, skip lists are better for concurrency because in a multithreaded environment, they can be implemented without locks to enable fast/optimal performance as compared to say red/black trees or B+trees.

            Here we have a "proper skip list" implemented in JavaScript, copied here for reference. The link has a nice suite of tests to show how it works.

            ...

            ANSWER

            Answered 2022-Feb-25 at 14:17

            The summary of your question is:

            • The meaning of group and node objects, and why they have their structure they do.
            • What the nodes array is doing on a group.

            I'll use an image taken from brilliant.org:

            The linked lists appear as horizontal bands, while the arrays appear as vertical stacks.

            A group corresponds to one distinct key in the set -- marked in yellow. The corresponding value is not depicted in the image, but is just payload and is not essential for understanding the data structure. A group has a nodes array -- displayed as a stack on top of the key. Each of these nodes belong to a different linked list in which they represent that same key. Those nodes have backreferences again to the group, so a node knows which key it represents, and which other linked lists have a node for this same key.

            So the nodes array actually duplicates a key to different lists. One nodes array does not represent different keys in the collection -- just one. It is like an elevator to jump from one train (linked list) to another, with the same key.

            The sizes of these arrays are randomly determined, but are intended to be small on average. This is driven by the stackUpProbability. It represents the probability that an array is extended with one more node (upwards in the image). The probability for having at least one node (for a key) is obviously 1, but the probability that the array will have at least one more node in it (and thus have a size of at least 2), is stackUpProbability. The probability that it will have size 3 is (stackUpProbability)²... etc.

            This way, the bottom linked list (at layerIndex 1) will have all keys in the collection (one node per key, in sorted order), but any next layer will have fewer keys, and the top layer might only have a hand full. The lists with fewer nodes provide a way to travel fast along the collection in search of a value. This provides a proximity of where a value could be found. Via the "elevator" a search algorithm can step down to lower (slower) linked lists and continue the search there, until it reaches the lowest level where the key will be found (if present), or where it would have been (if not).

            Source https://stackoverflow.com/questions/71134703

            QUESTION

            looping a list and skip from another list
            Asked 2022-Feb-20 at 20:51

            is there a better way to do this, this code is working but i feel like there is a better way to do it

            ...

            ANSWER

            Answered 2022-Feb-20 at 20:34

            Since you've already worked out how to build available you could just zip the two:

            Source https://stackoverflow.com/questions/71198347

            QUESTION

            C++ declaration and scope issues
            Asked 2021-Dec-19 at 14:53

            I encountered the error : error: ‘data_structure’ was not declared in this scope, when compile following codes.

            I assume errors happened in :

            • root = data_structure.insert(root, data[data_ind]);
            • data_structure.insert(data[data_ind]);
            • TreapNode *res = data_structure.search(root, search_data[s_data_ind]);
            • bool res = data_structure.search(search_data[s_data_ind]);

            But I don't know what I should correct.

            complete codes : https://gist.github.com/theabc50111/05651b8c125feaaff5f80f15deb535f4

            partial codes:

            ...

            ANSWER

            Answered 2021-Dec-19 at 14:53

            The variables data_structure and root are alive and visible only in block scopes pf if statements where they are declared as for example in this if statement

            Source https://stackoverflow.com/questions/70412247

            QUESTION

            Invalid Read Of size 8 when passing a string to a function
            Asked 2021-Dec-18 at 07:26

            Im a second year CS student and Im attempting to make a hangman game for fun during my winter break. Ive implemented the beginning of a menu class here, and yes I know this is too much oop for a project of this scope but I intent to reuse all these classes.

            Anyways valgrind is telling me an Invalid read of size 8 and it returns the following lines in order:

            menu::getName (menu.cpp:13) (this is at menu.cpp\getName()\return name;)

            menu::print() (menu.cpp:21) (this is at menu.cpp\print()\cout<<". return to "

            main (main.cppp:28) (this is at main.cpp\main()\thisMenu->print();)

            Im usually very good at solving these types of problems, and I searched the web but I couldnt find a solution and Im completely stumped. I feel like it could be a simple issue and Im missing something but Im not sure. Any help is greatly appreciated! Thanks!

            menu.cpp:

            ...

            ANSWER

            Answered 2021-Dec-18 at 07:18

            If you look at this line:

            Source https://stackoverflow.com/questions/70401573

            QUESTION

            C++ friend keyword not accessing non-static data member
            Asked 2021-Nov-03 at 21:59

            I need to overload the ostream operator with new functionality for a doubly linked Skip List class.

            When I cout the instance of my class, I want it to iterate through my the levels of my skip list, and wherever the head pointer is pointed to a nullptr I want it to print the level name and a status of empty.

            Would look something like:

            ...

            ANSWER

            Answered 2021-Nov-03 at 21:59

            SkipList::maxLevels_; refers to the static maxLevels_ member of the SkipList class. So, if you need maxLevels_ to be the maximum level of all the instances of SkipList you have to declare it as static. Otherwise in your overloaded friend function you have to use the private member of the list instance.

            Source https://stackoverflow.com/questions/69831913

            QUESTION

            A probability theory problem in skiplist's C implement
            Asked 2021-Oct-31 at 07:48

            These days I am looking at skiplist code in Algorithms in C, Parts 1-4, and when insert a new value into skiplist is more complex than I think. During insert, code should ensure that the new value insert into level i with the probability of 1/2^i, and this implement by below code:

            ...

            ANSWER

            Answered 2021-Oct-30 at 13:58

            Presumably RANDMAX is intended to be RAND_MAX.

            Neglecting rounding issues, half the return values of rand are above RAND_MAX / 2, and therefore half the time, the loop exits with i = 1.

            If the loop continues, it updates i to 2 and j to 4. Then half the remaining return values (¾ of the total) are above RAND_MAX / 4, so, one-quarter of the time, the loop exits with i = 2.

            Further iterations continue in the same manner, each iteration exiting with a portion of return values that is half the previous, until the lg_n_max limit is reached.

            Thus, neglecting rounding issues and the final limit, the routine returns 1 half the time, 2 one-quarter of the time, 3 one-eighth the time, and so on.

            lg_n is not defined in the routine. It appears to be a record of the greatest value returned by the routine so far.

            Source https://stackoverflow.com/questions/69780024

            QUESTION

            why Redis use skiplist to implement zset
            Asked 2021-Apr-02 at 08:36

            I study the implementation of Redis, I know that there are two data structure (skiplist and ziplist) behind zset. I know some basic idea of skiplist (keep multiple pointer to access next element faster, avg time complexity of search is O(logN)).

            My question is :
            I read the info said that there are two situations that Redis will use skiplist to implement zset, first : there are many members in zset, second : memebers in zset are long string.

            What's the benefit to use skiplist instead of ziplist in these two situations, why these two situations need special treatment? Why don't we always use one data structure to implement zset?

            ...

            ANSWER

            Answered 2021-Apr-02 at 08:36

            ziplist is O(n) time complexity for searching and updating and skiplist is O(logN)

            The only benefit for ziplist is memory usage. As zip list implement by linear memory address and no pointers to other nodes, it can save a lot of memory space for Redis.

            When you only have few members in zset, O(N) and O(logN) will not have significant difference. But memory usage will have huge differences(consider you have 1m keys of zset and each zset only have 10 members).

            And when there are a lot of members in zset(like 1m), time complexity is important since it will affect the concurrent performance.

            Source https://stackoverflow.com/questions/66914001

            QUESTION

            in DXL, how to get the handle of a module that I don't open myself in the DXL script
            Asked 2021-Mar-30 at 16:05

            I have a DXL script that open (read or edit) modules and put them in a skip list (so that I could close them at the end)

            The skip list store the module handle of each module read or edit :

            ...

            ANSWER

            Answered 2021-Mar-30 at 16:05

            Not sure if this is due to the excerpt you posted, but you should always turn off the autodeclare option and ensure that you always use the correct types for your variables by either checking the DXL manual or by using alternative sources like the "undocumented perms list" . data performed on a ModuleVersion returns type Module. So you already have what you need. An alternative would be the perm bool open(ModName_ modRef). And note that the perm module does not return a Module, but a ModName_. Also, in addition to bool isRead(Module m), bool isEdit(Module m) and bool isShare(Module m)(!!) when you really want to close modules that have been opened previously, you might want to check bool unsaved(Module m)

            Source https://stackoverflow.com/questions/66872828

            QUESTION

            Is there a elegant implement of the Iterator for the Rc> in Rust?
            Asked 2021-Feb-27 at 15:02

            When I tried to implement the SkipList by rust, I was trapped by the implement of Iterator of Rc>. Code is listed:

            ...

            ANSWER

            Answered 2021-Feb-27 at 15:02

            Is there a elegant implement of the Iterator for the Rc in Rust?

            Not really. There's two big things in your way.

            One limitation when building an Iterator is that the output type cannot reference the iterator itself. It can either return an owned value (no lifetimes involved) or return references bound to the lifetime of some other object.

            I see you've tried to communicate that you want to return Refs bound to the lifetime of the orignal SkipList by using PhantomData<&'a K> and also using 'a in your Iterator::Item. However, since your iterator can only source values from ptr, an owned value with no lifetime-linkage to 'a, the compiler will complain about mismatched lifetimes at one point or another.

            In order to do this, your iterator would have to use something bound to 'a, probably some form of Option<'a, _>>.

            However, another limitation is when you have nested RefCells, with each level that you iterate, you need to keep around an additional Ref. The reason being that borrows from a Ref don't keep the lifetime of the RefCell, but from the Ref itself.

            Source https://stackoverflow.com/questions/66279395

            Community Discussions, Code Snippets contain sources that include Stack Exchange Network

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            You can download it from GitHub.

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