I'm a beginner programmer in my first year of Computer Science.
I'm curious about the 32 bit and 64 bit systems, and how it affects developing software.
When I download software I need to choose between the two, while other software only has a 32 bit version.
Are there different ways of programming for a 64 bit system?
Is it compiled in the same way?
What are the main benefits of a separate 64 bit app?
Cheers
Are there different ways of programming for a 64 bit system?
Yes and no. No, in the sense that most of the time you should be able to write platform-independent code, even if you are coding in a language like C. Yes, in the sense that having knowledge of the underlying architecture (not just the word size!) helps to speed up critical parts of your program. For instance, you may be able to use special instructions available.
Is it compiled in the same way?
Again, yes and no. Compilers for systems languages work in similar ways for all architectures, but of course, the details differ a bit. For instance, the compiler will use knowledge about your architecture to generate as efficient code as possible for it, but also has to take care of differences between architectures and other details, like calling conventions.
What are the main benefits of a separate 64 bit app?
I assume you are asking about the usual desktop CPUs, i.e. x86 architecture, but note that there are other architectures with word sizes ranging from 8-bit to 128-bit. Typically, people would compile a program targeting a single architecture (i.e. for a given machine), and that's about it.
However, x86 is a bit special, in that the CPU can operate in different modes, each with a different word size: 16-bit, 32-bit and 64-bit (among other differences). Effectively, they implement several ISAs (Instruction Set Architectures) in a single CPU.
This was done to preserve backwards compatibility, and it is key to their commercial success. Consider that, when people bought the first 64-bit capable CPUs, it was most likely that they were still using 32-bit operating systems and software, so they really needed the compatibility. The other options are emulating it (poor performance) or making sure all the popular customer software has been ported (hard to achieve in ecosystems like Windows with many independent, proprietary vendors).
There are several benefits of 64-bit x86 over 32-bit x86: more addressable memory, more integer registers, twice the XMM registers, a better calling convention, guaranteed SSE2... The only downside is using 64-bit pointers, which implies more memory and cache usage. In practice, many programs can expect to be slightly faster in x64 (e.g. 10%), but pointer-heavy programs may even see a decrease in performance.
Generally speaking the main benefit of 64 bit application is that it has access to more memory. Having 32 bit pointer you can access only 4GB of memory.
Most modern compilers have option to compile either 32 bit or 64 bit code.
32/64 coding is the same unless you are dealing with huge in-memory objects, where you would need to use 64 bit specifically.
An interesting fact/example is that Unix time is stored as a single number. It is calculated as a number of seconds passed from January 1st 1970. This number will soon reach 32-bit size, so eventually we will have to upgrade all of our systems to 64-bit so they can hold such a large number.
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Actually I want to link 64 bit library to my 32 bit application.
I want to use a library which works faster under 64 bits under some circumstances. But i have to link that library to my 32 bit application . Is it possible or not ??
In a word, no. The only way to get compiled 64bit code talking to compiled 32bit code is via some form of IPC (e.g. pipe, named pipe, or network connection). That may well introduce performance bottlenecks of its own, so probably isn't worth the bother.
It is not easy as #robthebloke mentioned. But NVIDIA RTX Remix Runtime does it somehow, making older 32bit games running on 64-bit vulkan driver (bypassing 2-4GB virtual memory limit).
I am creating a quite simple application which reads and display text files and search through them.
I am asking myself if there is any interest for me to propose 32 and 64 bits version to the user.
Is the difference only in having access to more memory heap size with the 64 bit version or is there any other interest ?
Will a 32 bit compiled program work on a 64 bits JVM (I assume yes)
The only differences between 32-bit and 64-bit builds of any program are the sizes of machine words, the amount of addressable memory, and the Operating System ABI in use. With Java, the language specification means that the differences in machine word size and OS ABI should not matter at all unless you're using native code as well. (Native code must be built to be the same as the word-size of the JVM that will load it; you can't mix 32-bit and 64-bit builds in the same process without very exotic coding indeed, and you shouldn't be doing that with Java about.)
The only times that have swung it for me is when there have been native libraries involved that have pushed it one way or the other. If you're just in Java land then realistically, unless you need >4GB of heap size, there's very little difference.
EDIT: The differences include things like it uses slightly more memory than 32 bit, significantly more if you're using a version before 6u23 and aren't using -XX:+UseCompressedOops. There may also be a slight performance difference between the two, but again nothing huge.
Can I use the assembly routines for Serpent encryption in the link below written for 32-bit x86 from a 64-bit program on an x86-64 machine? That is, without launching a separate 32-bit process for it? If not, does anyone have a pointer to an optimized implementation of Serpent that works in both 32 and 64 bit (LGPL is OK but cannot use GPL since it's a commercial project)?
http://gladman.plushost.co.uk/oldsite/cryptography_technology/serpent/serpent.asm
You will need to convert the portions of the code that transfer the results and data to/from memory to use 64-bit address registers. Also, stack manipulation code will need to use the 64-bit stack registers. Other than that, it's likely to work without major changes.
This code seems compatible, at least for me (generally, IA32 assembly is pretty backward-compatible, as sizes of registers do not change, there are just new ones added on x86-64). Also, best way is to check it by yourself.
X86 and AMD64 are the most important architectures for many computing environments (desktop, servers, and supercomputers). Obviously a JIT compiler should support both of them to gain acceptance.
Until recently, the SPARC architecture was the logical next step for a compiler, specially on high-end servers markets. But now that Sun is dead, things are not clear.
Oracle doesn't seem to be really interested in it, and some big projects are dropping support for that architecture (Ubuntu for example). But on the other hand, the OpenSPARC initiative intended to open source recent processors is quite promising, meaning that a lot of manufacturers could implement and use SPARC for free in the near future.
So, is SPARC still a good choice as the next target architecture for a JIT compiler? Or is it better to choose another one (POWER, ARM, MIPS, ...)?
I don't know any more than you about SPARC's future. I hope it has one; it's been tragic how many good architectures have died out while x86 has kept going.
But i would suggest you look at ARM as a target. It isn't present in big server hardware, but it's huge in the mobile market, and powers all sorts of interesting little boxes, like my NAS, my ADSL router, and so on.
Your next target architecture should definitely be ARM - power consumption in large datacenters is a huge issue and the next big thing will be trying to reduce that by using low-power CPUs; see Facebook's first attempt on this.
Prety straight forward, are the Intel compilers worth getting? I do mostly systems level and desktop work so I figure I might benefti. Can anyone with some more experience shed some light?
If you are on Windows, they do provide a nice speed boost over other compilers on Intel processors. There is a known behavior where they pick a very slow code path with non-Intel processors (AMD, VIA), and antitrust probes surrounding the issue.
If you use the thread building blocks or other features, you also risk tying your code to the Intel compiler long term as the functionality doesn't exist elsewhere.
GCC 4.5 on Linux is nearly on-par with the Intel compiler. There is no clear winner on that platform.
In the small experience I've had with intel compilers (C only), I would say their are vastly superior. Specifically the OpenMP library was much much faster than the open source version. "Worth it" depends on your situation though, they are expensive, but they are better IMO.
From the benchmarks I've seen, it does look like using the Intel specific compilers provide some performance/multithreading benefit over their Open Source alternatives.
if floating number precision is important to you then use Visual studio compiler and not intel compiler.
32 bit vs 64 bit application Can give you different result on calculation with Intel compiler. (checked).
Visual studio compiler result on 32 bit vs 64 bit will be same.
If you're comparing the numerical behavior of ICL vs. MSVC++ you must take into account the different behavior of the /fp: settings.
ICL /fp:source (less aggressive than default) is equivalent to MSVC /fp:fast (more aggressive than default).
Microsoft doesn't perform any of the optimizations which are enabled by ICL default. These include simd reductions (which usually improve accuracy, but by an unpredictable margin). ICL also violates the standard about parens by default. There still seems to be a controversy about whether to fix that by better performing means than /fp:source.