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is python slower than java/C#?
Ignoring all the characteristics of each languages and focusing SOLELY on speed, which language is better performance-wise?
You'd think this would be a rather simple question to answer, but I haven't found a decent one.
I'm aware that some types of operations may be faster with python, and vice-versa, but I cannot find any detailed information on this. Can anyone shed some light on the performance differences?
Java is faster than Python. Easily.
Python is favorable for many things; speed isn't necessarily one of them.
References
python.org/Language Comparisons
C++ vs Java vs Python vs Ruby : a first impression
A subjective analysis of two high-level, object-oriented languages: Comparing Python to Java
If you ignore the characteristics of both languages, how do you define "SPEED"? Which features should be in your benchmark and which do you want to omit?
For example:
Does it count when Java executes an empty loop faster than Python?
Or is Python faster when it notices that the loop body is empty, the loop header has no side effects and it optimizes the whole loop away?
Or is that "a language characteristic"?
Do you want to know how many bytecodes each language can execute per second?
Which ones? Only the fast ones or all of them?
How do you count the Java VM JIT compiler which turns bytecode into CPU-specific assembler code at runtime?
Do you include code compilation times (which are extra in Java but always included in Python)?
Conclusion: Your question has no answer because it isn't defined what you want. Even if you made it more clear, the question will probably become academic since you will measure something that doesn't count in real life. For all of my projects, both Java and Python have always been fast enough. Of course, I would prefer one language over the other for a specific problem in a certain context.
There is no good answer as Python and Java are both specifications for which there are many different implementations. For example, CPython, IronPython, Jython, and PyPy are just a handful of Python implementations out there. For Java, there is the HotSpot VM, the Mac OS X Java VM, OpenJRE, etc. Jython generates Java bytecode, and so it would be using more-or-less the same underlying Java. CPython implements quite a handful of things directly in C, so it is very fast, but then again Java VMs also implement many functions in C. You would probably have to measure on a function-by-function basis and across a variety of interpreters and VMs in order to make any reasonable statement.
Different languages do different things with different levels of efficiency.
The Benchmarks Game has a whole load of different programming problems implemented in a lot of different languages.
Related
Someone told me there was more overhead for Java because you can essentially run it on most operating systems and that C# doesn't have that overhead so then it can execute at near C++ speeds.
So is there more overhead in Java, or does each OS has it's own overhead for it's JVM implementation?
C#, Java (and I'll toss it in there too - JavaScript) are languages. Languages are not fast or slow, they just are specifications for how we humans write things that are to eventually be handled by a computer.
The JVM is the Java Virtual Machine. But there are several different versions of it. There's HotSpot (the original), OpenJDK, And then one can look at JRockit from BEA, Apache Harmony and a bunch more.
For C# there is the CLR, but there's also Mono's runtime. There are also others that have been abandoned over time.
JavaScript (because I'm tossing that in there) has an entire army of runtimes. Some of those runtimes are faster than others.
It is the runtime that is faster or slower than another - even possibly for the same language. But that one is 'cross platform' and another is not is not enough of an indication to say that one is faster than the other. There are a great many other things at work and benchmarks can be constructed that show one combination being faster than another for each one.
Going even further, one can look at languages that span multiple runtimes. You've got Python with CPython as its default implementation - but there's Jython that runs in the JVM and IronPython that runs in the CLR. Similar examples can be found with Ruby, IronRuby, and JRuby or Clojure which can be compiled to JavaScript via ClojureScript and then run on one of the JavaScript runtimes rather than a JVM.
Again, its not the language that is fast or slow - but rather how its implemented in its runtime.
The Java language and the Java Virtual Machine (JVM) are completely separate entities. Oracle has done an excellent job of separating the two, so that other languages (like Scala or even Ruby) can run on the JVM.
The Java language itself is definitely written with the intent of targeting the JVM, but, so far as I know, there is no actual requirement that it must. So far as I know it's completely possible to write a Java compiler that generates native code, rather than Java bytecode. (This is all completely hypothetical. I've never heard of anyone actually doing that - there would be very little point. Current implementations of the JVM tend to be almost as fast as native code, and any benefit gained by this would be greatly outweighed by the loss of portability it would entail.)
The situation is further complicated by the fact that C# doesn't exactly have a VM, as discussed here. So the best comparison you can make is "does this implementation of the JVM run this Java code faster than that implementation of the .NET framework runs that C# code?"
In the end, unless there is a remarkable speed difference for very similar code, the comparison just isn't that compelling because there are too many variables. Use a different JVM, or a different Java compiler, or a different .NET implementation, or a different C# compiler, or run the same code on a different machine, and the numbers change.
Just curious about speed of Python and Java..
Intuitively, Python should be much slower than java, but I want to know more...Could anybody give me more? or introduce some nice post to read?
The current standard implementation of Python (CPython) is slower than Java because the standard CPython implementation doesn't have a powerful JIT compiler. Yet.
There have been several projects with the aim of producing a faster implement of Python:
Psyco
Unladen Swallow
PyPy
From what I've tried some of these projects can give very good speed ups for specific algorithms, but you still won't get it to run as fast as Java for typical application code. Most of the current effort seems now to be directed towards PyPy.
The lack of a JIT mentioned is one reason, but another reason is that Python is dynamic. Yes, that does make the language slower. You can see for yourself by using Cython.
A function written in Python can often be compiled to C with Cython. It makes it faster. But it get's really fast when you start adding type information to the variables and parameters, as both Cython and the C-compiler can start applying various simple optimizations that you can't do when the types are dynamic.
So one part of the difference is the inherent dynamicism of Python.
On the future: Python 3 has function annotations: http://www.python.org/dev/peps/pep-3107/ I expect that in a couple of years time, the JIT compilers like PyPy and UnladenSwallow will use this information, and you'll see Python being just as fast as Java, and with some careful applying of Cython, even faster. :)
I do not have data points to give, but one interesting aspect is that there are Python implementations on JVM (ditto for many other dynamic/scripting languages) -- JPython and Jython for example. This could allow some Python applications to run at speeds comparable to native Java applications, assuming implementation of Python runtime itself (on JVM) is efficient.
There are many great answers here as to why Java is faster than Python, 2 of the most common answers are that Python is dynamically typed, and that Java has several extremely powerful Just-in Time Compilers (2 Production quality, several experimental and not for general use) in it's arsenal, with only the C# Common Language Runtime capable of matching it. This is true, but even so, there is one last reason as to why Java is still faster, and oddly enough, it has to do with differences in how Java's Interpreter is designed, vs Python's Interpreter.
Right now, this is the source code of the Interpreter in production for the OpenJDK/HotSpot JVM, Java's reference implementation (There is actually another legacy Interpreter in the JVM source code which was the old one written by James Gosling himself way back when Java was first created, but that one is outdated and not compiled into the actual binary unless you compile it from source with special flags for debugging purposes. Interestingly enough, this is the interpreter responsible for earning Java the reputation of being horrendously slow back in those days):
https://github.com/openjdk/jdk/blob/master/src/hotspot/share/interpreter/templateInterpreter.cpp
This, in contrast, is the code segment of the CPython interpreter that executes Python opcode:
https://github.com/python/cpython/blob/master/Python/ceval.c#L1847
Notice something different between the 2?
While CPython has a massive for loop with a switch case for every single opcode possible (This is true for almost every other interpreter out there actually, other than Java), there is not a single loop, if else, or switch case in Java's Interpreter. Why is this?
The answer is that Java's Interpreter is a special type called a Template Interpreter, which to date is the only one of it's kind. Unlike most designs, instead of a switch case to evaluate Java bytecode, Java's Interpreter has a big arraylist of bytecode, mapped to native machine language when the application is started. This way, the Java Interpreter doesn't need to evaluate bytecode at all, it just inserts the bytecode as an array index, loads native machine language, and directly runs it on the CPU. This means Java's "Interpreter" is actually a discount Compiler, since it runs your code directly on the hardware. CPython on the other hand, like many other interpreters today, is a run of the mill bytecode interpreter, which processes python opcode in software. This obviously makes Python slower to run than Java, even without JIT.
As to why Java has such a unique Interpreter design not used anywhere else, it's because it needs to run interpreted code directly with JIT Compiled code seamlessly, and the ingenious design of having the Interpreter contain a table with bytecode->machine language pairs rather that directly execute it in software was the best way to achieve this goal.
With Java 1.6 out can we say that performance of Java 1.6 is almost equivalent to C++ code or still there is lot to improve on performance front in Java compared to C++ ?
Thanks.
Debian likes to conduct benchmarks on this sort of thing. In their case, it appears that Java is about half as fast and consumes 2-18 times as much memory as C++.
A well-written Java program is never going to be as fast as a well-written C or C++ program. The virtual machine is an irreducible overhead. However, most code is not well written.
Java is a simpler language than C++, and offers a more forgiving environment for inexperienced programmers - so if your programmers are inexperienced (and cheap), then Java will probably perform 'better' than C++.
shared_ptrs offer a similarly forgiving environment in C++, so they are very tempting for inexperienced programmers, or those migrating from Java, But their performance overhead is as bad or worse than Java's garbage collection. I've seen large C++ programs where every variable is a shared_ptr, and they perform terribly.
My opinion
Personally, I think that large projects need to choose an 'easy' programming language for the bulk of their code, and a 'fast' one for sections that need optimising. Java may be a good choice for the 'easy' language, especially since there is currently a plentiful supply of Java programmers - in the future, I think even easier languages such as Python will begin to take over.
C++ is a reasonable choice for a 'fast' language if you already know it, but I think it's over-complexity will eventually see it fall by the wayside, while C will continue to fulfill this role.
I would expect that most of the time for most applications C++ will be faster than Java.
In some cases there will be some C++ which is slower than Java for a given task. This is pretty rare and always a result for poor implemntation or more commenly poor refactoring of an application.
In the majority of cases the performance difference more than offset by the fexibility, ease of use, availability of libraries, and, portability that Java provides.
In a very few cases performance is so critical that developing in Java would be a poor choice <opinion><flame off>in these cases plain C is usually a better choice than C++ </flame></opinion>.
Currently the sweetspot in performance/ease of use/ease of development tradeoffs is C#. Portability is a big issues here though.
I find that Java performs very well.
However, why has no one ever fixed my biggest complaint?
Java uses FIVE TIMES as much memory as a C++ program doing the same job. At least!
And once it's used, Java keeps it!
Please, please, why won't anyone write a garbage collector for Java that uses minimum amounts of RAM? It could compact the heap and returns the memory to the OS. Instead of ridiculous piles of -Xm* options, use the memory needed and then give it back!
Actually I am sure some of the embedded system JVMs do this, but none of the desktop or server systems do.
This memory piggishness makes Java applications all want to act as if they own the entire computer system, that no one ever wants to run more than one application and that RAM is free and infinitely upgradable.
Therefore, no matter how great the performance, I would never write anything like a utility program in Java. Only gigantic server apps need apply.
What program are you developing?
Comparing C++ to Java speed is like comparing a screwdriver and a hammer, pointless. In the world we live in, where both supercomputers and toasters need to be programmed, you need to focus on your particular requirements.
I use C++ for hard realtime software running on embedded systems. I wouldn't dream of using the awfully broken Java for realtime spec for at least another 5 years, when it will hopefully be mature. I would be equally loath to use C++ for a database, cloud accessing middleware app (actually I have no Idea what I just said, but I know Java is good for 'that sort of stuff')
Would you use a ferrari with no trunk space to move your belongings? Would you bring a minivan to a drag race?
People have to understand that just because they are programming languages, does not mean they are comparable in a meaningful way.
No. Unless you measure it, you may not say it.
Performance is usually "good enough" for most purposes. The question is what you want to compare exactly, and if you have applied a profiler to find and fix the hotspots in your code.
JVM's based on Sun's code still pay a hefty startup-tax (I still wonder why they cannot snapshot that and restart from there) but Suns approach has been correctness first, speed second, and it's taken them 10 years to get up to par.
So the answer is "It depends" :)
For most applications it is almost certainly possible to write a C++ program which performs considerably better than a program to achieve the same thing in java.
However if the program isn't optimised for speed then java will likely be just as fast or faster because the compiler / JIT is able to make optimisations that a C++ environment can't.
Basically if you are willing to spend considerable time understanding and coding for performance you can probably do a considerably better job in c++ eventually than you could in java but for the same amount of time and effort it is quite likely that java will "win".
As usual though, algorithmic improvements tend to make as much if not more difference than the language.
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What is the difference between Java and C++? Are both object-oriented?
This is far too general a question to be answered here.
Java is an explicitly object-oriented language, with the harder-to-use bits snipped off.
C++ is a multi-paradigm language with the safety off. You can do object-oriented programming in it, as well as procedural and generic.
If you had a more specific question, we could be of more help. Why did you ask? If you want recommendations for a particular platform, or project, or whatever, we could be more responsive.
A C++ programmer will tell you that Java is rubbish. A Java programmer will tell you that C++ is rubbish. Therefore I conclude that they are indeed the same thing.
Each language designed with different purposes in mind, so IMO it's not fair to compare the two from one perspective, and ignore the other.
Generally speaking, C++ is an open standard, designed for implementing high performance systems where speed and performance and critical, there are lots of impressing projects designed using this language like Phoenix Lander, Adobe Acrobat Reader and others. C++ gives the developer the ability to program using a very high level abstraction -using generics for example, and, when needed, go down deep to the bare metal of the machine -to handle an interrupt for instance.
Java was designed with other purposes in mind, when Sun was planning Oak (later called Java), it focused on web applications so it supported the language with a bunch of heavy libraries of easy-to-use interfaces considering that. and portability (Compile once, run anywhere) using JVM, which prevents the programmer from coding to specific machine, but instead coding to a sandbox which in turn runs the code on the hosting machine, and this has obviously negative reflections on performance/speed.
Comparison of those two language is a popular cause of debate between programmers, and this is due to their different working demands and nature, IMO every language has made mistakes in order to mature, for example, C++'s exported templates, and Java's lack of procedural programming (Big Mistake). plus, each one has its pros and cons regarding different aspects, hence the one that balance productivity/performance issue IS the right language.
For more information Wikipedia's comprehensive article on Comparison of Java and C++
It might be interesting to take a look at what languages are used (and being used) to create major systems (like Google) from here.
One of the most important differences hasn't been mentioned yet - one is compiled to machine code, the other is compiled to bytecode which is interpreted by a virtual machine.
Everything is Object in Java as everything is derived from java.lang.Object But this is not the case in C++
No pointers in Java whereas C++ has provide support for pointers
No destructors in java (Java has automatic garbage collection) but C++ has destructors to do that
Thread support is built in Java but not in C++
No scope resolution operator in Java
No Goto statement in Java
No Multiple Inheritance allowed in Java but C++ allows that
No operator overloading is allowed in Java but C++ allows that
Java is interpreted for most part and hence Platform independent
Both are object oriented but they are very different languages. This probably isn't the best forum to ask for the differences... I would suggest you look both up on Wikipedia and review the descriptions there. You will be able to see the differences very quickly for yourself.
I love c++ but unless you absolutely need to use c++ then use something else. When you need to use c++ then you will know the difference, Grasshopper.
(hint do not write device drivers, video decoders, encryption libraries, 3-d graphics engines or language run-time engines in java).
Yes, both are object oriented programming languages.
C++ is an evolution to C. Which was a system programming language. C++ Added many features to the language to make it object oriented. It became the mainstream programming language for that reason.
Java is an evolution of C++, with different goals ( cross platform for instance ). It remove some of the features that make C++ so hard to learn. Simplify others and remove others.
The main difference is C++ programs are compiled directly to machine code ( understood by the CPU ) while Java programs are compiled to be run in a "Virtual Machine" the JVM most of the cases. For these reasons java programs were interpreted by another program and at the beginning were veeeery slow programs. Nowadays the VM may optimize this code and make it run very very fast.
See this link.http://www.javacoffeebreak.com/articles/thinkinginjava/comparingc++andjava.html
Gross but accurate oversimplification: Java is easier. C++ is faster.
Just a quick addition to what David Thornley posted. C++ is a procedural language that supports Objects and OO design. Java is pure OO. Java does less but on more.
I've had little exp. with java and since now i've worked with c++. what makes this one more special and preferred?
Moreover I would like to know about the use of System.in classes and parseInt classes.
Java is vastly easier to work with, especially when developing large programs.
Debugging: Java generates nice Stacktraces
Stability: You can catch every exception
Development Speed: you need no linker (which can take many minutes in C++); with a modern IDE (e.g. eclipse) you can edit code in-place while the program is running
Garbage Collection and run-time type safety eliminate whole classes of errors
really good free (as in beer) IDEs
In theory (and sometimes in reality) Java programs also run on multiple platforms, "write once - debug, er, run everywhere" type of thing. That makes it very useful for a variety of projects.
In my personal experience, while learning Java shortly after being introduced to C++, Java seemed simpler and easier to learn and understand, hence more productive, as was said before. While program structure and syntax is very similar, there is no need to worry about pointers and other potentially dangerous language features.
This is really very broad and I think these are really 2 or 3 different questions. I'll address the first one very briefly. Java utilizes garbage collection, or autmatic memory management. That is, arguably, the biggest difference between it from a language like C++. There are clearly some potential for increase in productivity in that you don't have to worry as much about memory, although in reality you do need to pay attention to your references. Perhaps you could refine your question a bit.
Java works in browsers! (Milpa for example). You can say Flash too, but with Java you can leverage the numerous classes coming with it (another advantage over C++, even if both languages has a good set of free libraries on the Net) and your knowledge of the language.
As said, Java is supported on many platforms with minimal adjustments, with a fast, efficient VM, from big servers to mobile phones.
OO support is arguably better designed, avoiding mistakes done in C++. Somehow, C# is to Java what Java is to C++ ^_^ (I won't argue on this, I don't know C# enough actually, it is just an historical point).
In the same spirit, Java is slightly more abstract, avoiding pointers, manual memory management and some other low level stuff.
That doesn't mean than one is better than the other, STL helps C++ for some of the issues above, etc.
I am not sure how to answer the last sentence, these are object and method respectively, not classes.
I never used System.in yet, I suppose it is usable if you feed the Java program with < or | on the command line. And parseInt is a static method of Integer class.
The language features have already been mentioned (GC, reflection etc.). But there is another major difference: Libraries. I know there is the STL and Boost and all kinds of libraries out there, but they are not all of a piece, they all feel different. Often you are forced to use all kinds of C-APIs (e.g. threading or sockets, just to mention two things). All the C++ evangelists will now jump in and tell about some kind of cool OO-socket or OO-threading library, but they are not part of the STL. They should be. Its almost 2009 and everything is networked and multithreaded. This ought to be part of the standard library.
Why is it bad to use those C-APIs? Because it is hard to use them in an object oriented programm. Try using Win32's CreateThread() with the listener-pattern (C#-users: read "delegates").
For a "rich client application", where performance is not a big deal, I would always use Java or C#. If I need raw speed (think signal processing or embedded applications), I would rather use C instead of C++.
BTW: I have used all four languages (C, C++, Java, C#) for a long time.
If you like to program really the object oriented way, then you need to go from C++ to Java. One of the problems with C++ is that most programmers actually use it as C and don't exploit all its OO features. Java is here stricter.
With C++ you're programming "on the metal", whereas with Java you're programming towards a virtual machine. The Java software stack all the way down to the VM is constructed to give a highly abstracted programming experience. This is most clearly apparent in the use of datatypes "that just are" (i.e. the programmers need no understanding of how they translate into memory areas), garbage collection "that just works" (the programmers don't have to deal with allocation and deallocation issues) and the ubiquity of exceptions for error handling and propagation. Pointers are not part of Java, the system takes care of where and how things are allocated.
From this, you might see that the design philosophy of Java is very different from C++: Java tries to enforce that the programmer should stick to certain ways of working which are considered to be safe and to make programming easier. Some people hate this aspect of Java, other people love it.
It really depends on what you're trying to do.
For a lot of higher level functionality where optimal performance may not matter, Java is easier and more reliable to use. For example, garbage collection, array checking, etc. It's also sandboxed, of course.
For me, another major benefit of Java is the use of reflection and of run time class loading. I write a lot of plugins within pluggable architectures, and can ensure I can add more new classes to a running program on any platform. Last time I tried to do that in C++, I had to mess with DLLs and COM.