Hey guys, I am trying to familiarize myself with multi-processor coding. So I created a C++ project in Visual Studio to get on my way with it. However, for textboxes it uses this weird String ^ object type. Been trying to figure out how to convert it into a int, or char* or something else, but nothing works. Does anyone know anything about this. Google wasn't very helpful.
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Visual Studio C++
- Thread starter coder_t2
- Start date
You're probably creating a .NET Managed C++ project where C strings aren't really allowed as they aren't managed. Programming in .NET is very different from standard C++ and you need to use the .NET class library and types instead of the standard C++ libraries.
Tawnos
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Handle (^)
http://msdn.microsoft.com/en-us/library/yk97tc08(VS.80).aspx
gcnew (garbage collected new)
http://msdn.microsoft.com/en-us/library/te3ecsc8(VS.80).aspx
Interior pointer (aka handle/hat)
http://www.codeproject.com/KB/mcpp/interiorpointers.aspx
That's really lame. I am trying learn some new skills for future jobs. I doubt C++ .NET is used much by companies. Usually C# if using .NET. Think it is worthwhile to learn how to do multi-threaded apps in C#?
Tawnos
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Why do you doubt that? It gives you many to all of the benefits of .NET with the native ability to use existing c++ libraries and system calls...
I guess because it using these weird self contained pointers for String, which is what is returned by the Text property of many .NET visual objects. But since .NET isn't all Windows Form stuff, I retract my original statement about companies not using .NET C++. I was just getting frustrated with it. I am just using C# atm to learn multi-threading. At least I'll understand concepts, and the syntax won't be that different for C++.
Ok. So I have been playing threading in C# and I got it to work nicely enough. Just been doing some basic stuff to understand it. But I want to be able to utilize multiple cores on a computer. What keywords should I use to find a tutorial on google for this. At first I thought multi-threading was it, but apparently not.
What's the problem? Are you trying to say that your threads are not using multiple cores? They should be.
They aren't, at least it appears that way. The multi-threading does make things smoother. Like no lockups and such, but it isn't using 100% CPU, only 50%. Just as it was before I added threading. I am just doing a simple of having a for loop go through a count, and a label to output each number. There are 3 labels and each has a loop that runs simultaneously.
ok new question. Anyone know how to calculate numbers larger than 64 bits? Been using Int64, but I want to calculate numbers larger than that. Trying to do it via a string, but it is proving to be a lot of work since I have to custom create every math function.
There's nothing included in the standard libraries to help with this, and obviously no primitive types. Either build a large integer class (there are a bunch of ways to implement it...), or use one of the libraries available to you. In .NET you'd use BigInteger, though most other libraries will have similar classes available. Or if you want to stick to standards compliant C/C++ and don't want to implement it yourself you could use GMP.
Tawnos
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It's a good exercise to figure out how to do large math. Even simple things such as addition and subtraction. Try creating your own math library and overload the functions, starting with + and - then moving on. You might find it very rewarding.
Alternatively, grab a pre-rolled library (such as those keenan recommended) and go for it.
I agree. I wouldn't mind seeing some example code. Or even a general concept. Currently I am just trying to do it with strings. Not really doing it as good as I would like. But just trying to get the Mersenne Prime algorithm rocking. And the only point of that was to test multi-threading. Lol. Funny how this project keeps evolving and I need to keep creating new things.
For a simple implementation, think back to how you learned to do arithmetic in grade school. The algorithms you will need to implement are similar; you will need to handle carrys and so on in the same fashion while looping over the digits. There are much more efficient approaches that can leverage the built-in 32 and 64-bit arithmetic operations and do some further tricks, but the naive approach is fine and a good learning experience, it's a pretty standard assignment in early comp sci courses.
Strings are not a bad representation for the naive approach, though it might make life a little easier to think of the string as an array if int8's instead, that way you're not translating between ASCII and binary all the time, just storing a single 0-9 digit as an 8-bit integer. If you want to get clever, you can pack two digits into a single byte. Even using ASCII strings though you're heading down the right path (at least for the sensible, but inefficient approach) of treating a large integer as an array of digits, now all you need to do is translate your basic artihmetic skills to C methods
.
Strings are not a bad representation for the naive approach, though it might make life a little easier to think of the string as an array if int8's instead, that way you're not translating between ASCII and binary all the time, just storing a single 0-9 digit as an 8-bit integer. If you want to get clever, you can pack two digits into a single byte. Even using ASCII strings though you're heading down the right path (at least for the sensible, but inefficient approach) of treating a large integer as an array of digits, now all you need to do is translate your basic artihmetic skills to C methods
.
Tawnos
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e.g. To add 2 8 bit (1 byte, aka "char" in c/c++) numbers with overflow:
Code:
10000000
10000000
--------
100000000Which could be represented by an array containing:
[0] 00000000
[1] 00000001
To do the math, then, you need something bigger than your number... the easiest is to go twice as big, so use a short to store the result of two bytes. You can then store the lower and upper parts using masking and shifting.
e.g.
short added = byte1 + byte2;
array[0] = (char)(added & 0xff)
array[1] = (char)( (added >> 8) & 0xff)
Make sense?
So I created a unlimited sized integer class using strings. It works, albeit very inefficiently. So I am working on creating a more efficient class. I like the idea of doing bit shifting. But how do you represent a number back to decimal, if you were using an array for bits?