473,724 Members | 2,212 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

hash_map vs unordered_map

Hi,
I am wondering if there are any functional differences between SGI's
hash_map and tr1's unordered_map. Can these two containers be
interchanged? What would it take to switch from hash_map to
unordered_map? Thank you.
-Marek
Aug 28 '08 #1
2 8140
On 28 ago, 16:30, marek.vond...@g mail.com wrote:
Hi,
I am wondering if there are any functional differences between SGI's
hash_map and tr1's unordered_map. Can these two containers be
interchanged? What would it take to switch from hash_map to
unordered_map? Thank you.
Hi.

It's not clear to me what exactly is your doubt. Just like SGI's
hash_map the "new" unordered_map is also based on a hash table. Since
hash_map (and hash_set, hash_multimap, hash_multiset) is not standard,
several compilers have provided their own implementation (GCC's for
example is based on SGI's hash map). Usually the implementation
differs in some aspect, even related to the interface (including the
template parameters), and are located in an extended namespace.

There're implementations of TR1 with support for unordered_map. IIRC
Boost's TR1 lacked this particular data structure (I'm not sure if
it's there yet), but Visual Studio's 2008 feature pack does included
it. You might wanna try one of those so you can check out the
differences.

Well, does this help at all?

--
Leandro T. C. Melo


Aug 29 '08 #2
On Aug 29, 8:17*am, Leandro Melo <ltcm...@gmail. comwrote:
On 28 ago, 16:30, marek.vond...@g mail.com wrote:
Hi,
I am wondering if there are any functional differences between SGI's
hash_map and tr1's unordered_map. Can these two containers be
interchanged? What would it take to switch from hash_map to
unordered_map? Thank you.
It's not clear to me what exactly is your doubt. Just like SGI's
hash_map the "new" unordered_map is also based on a hash table. Since
hash_map (and hash_set, hash_multimap, hash_multiset) is not standard,
several compilers have provided their own implementation (GCC's for
example is based on SGI's hash map).
Right. GCC provides SGI style hash_map under the name
__gnu_cxx::hash _map, MSVC with Dinkumware C++ library under the name
stdext::hash_ma p. The Dinkumware version differs from the SGI's
hash_map in certain minor details, but wrappers can be written so that
it would behave as SGI's hash_map. Now, my question is if the same
thing can be easily done with unordered_map, such that the wrapper
would have the same external interface like SGI's hash_map and provide
same guarantees about iterator invalidations, etc. I have an existing
code base that assumes that there is a class ext::hash_map that has
the semantics of SGI hash_map and that maps either to
__gnu_cxx::hash _map, SGI's hash_map, STLPort's hash_map or a wrapper
around stdext::hash_ma p. I would like to extend this so it could be
mapped to tr1::unordered_ map as well.

-Marek
Aug 30 '08 #3

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

4
5841
by: Christian Meier | last post by:
Hello, Yes, I know that hash maps aren't in the standard. But I couldn't find any better newsgroup for this post. (or is there an SGI library newsgroup?) I am currently testing the hash_map implementation of SGI. And now I am not sure if it is really true, what I discovered.... Here is my code:
5
8618
by: peter_k | last post by:
Hi I've defined hash_map in my code using this: ------------------------------------------- #include <string> #include <hash_map.h> & namespace __gnu_cxx {
10
7903
by: g | last post by:
hello! I wanna replace an std::map<std::string,Services*> with hash_map.How I will do this? any link with examples? transactions.insert(std::pair<std::string,Services*>("Aservice",new xxxx)); transactions.insert(std::pair<std::string,Services*>("Vservice",new
1
2971
by: anjangoswami06 | last post by:
Hi, I am interested to know how it is possible to update the data type with "insert" with stl hash_map. Suppose we have, hash_map<const char *, MyDataType, hash_compare<const char*, some_compare_func_obj>> x; //I want to insert a new instance of MyDataType if a new key is encountered but if it is a key //which already exists I want to update
4
4314
by: Paulo Matos | last post by:
HI all, I'm using unordered_map from TR1. I have a table variable which is a private member of a template class: template<typename K, typename D, typename EQ> class FooClass { public:
4
4909
by: yuyang08 | last post by:
Hello, everyone, I am wondering what is the hash function that is used in hash_map/hash_set. Can I replace it with my own hash function? Any comments on this? Thanks! -Andy
6
8606
by: Rares Vernica | last post by:
Hi, I am using tr1/unordered_map in my code. My code compiled ok on g++ (GCC) 4.1.2 (Ubuntu 4.1.2-0ubuntu1). Now I need to compile my code on g++ (GCC) 4.0.3 (Ubuntu 4.0.3-1ubuntu5). I get a messy error. Here are what I try to do: typedef unordered_map<string, unsignedStringHash;
4
4124
by: lokki | last post by:
Hello, can anybody tell me what's wrong with following example code? char *k, *v; k = new char; strcpy(k, "a2"); v = new char;
4
3407
by: James Kanze | last post by:
On Jul 16, 10:53 pm, Mirco Wahab <wa...@chemie.uni-halle.dewrote: It depends. You might like to have a look at my "Hashing.hh" header (in the code at kanze.james.neuf.fr/code-en.html---the Hashing component is in the Basic section). Or for a discussion and some benchmarks, http://kanze.james.neuf.fr/code/Docs/html/Hashcode.html. (That article is a little out of date now, as I've tried quite a few more hashing algorithms. But the...
0
8741
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
9389
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
1
9160
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
0
9090
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
8063
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
1
6689
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
5996
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
0
4771
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
3
2149
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.