The m[line][column] = 12 syntax is ok (provided line and column are in range). However, you didn’t write the code you use to allocate it, so it’s hard to get whether it is wrong or right. It should be something along the lines of m = (int**)malloc(nlines * sizeof(int*)); for(i = 0; i < nlines; … Read more
You’re absolutely right. Your c array in the second example is being allocated on the stack, and thus the memory will get reused immediately following. In particular, if you had code like printf(“%s\n”,greet()); you’d get weird results, because the call to printf would have reused some of the space of your array. The solution is … Read more
First, note that Go, itself, doesn’t always shrink its own memory space: https://groups.google.com/forum/#!topic/Golang-Nuts/vfmd6zaRQVs The heap is freed, you can check this using runtime.ReadMemStats(), but the processes virtual address space does not shrink — ie, your program will not return memory to the operating system. On Unix based platforms we use a system call to tell … Read more
Yes, first define a custom allocator: template <class T> class SecureAllocator : public std::allocator<T> { public: template<class U> struct rebind { typedef SecureAllocator<U> other; }; SecureAllocator() throw() {} SecureAllocator(const SecureAllocator&) throw() {} template <class U> SecureAllocator(const SecureAllocator<U>&) throw() {} void deallocate(pointer p, size_type n) { std::fill_n((volatile char*)p, n*sizeof(T), 0); std::allocator<T>::deallocate(p, n); } }; This allocator … Read more
Well this is expected of any efficient data storage: the words have to be indexed in memory in a dynamic data structure of cells linked by pointers. Size of the structure metadata, pointers and memory allocator internal fragmentation is the reason why the data take much more memory than a corresponding flat file. A Redis … Read more
As a sanity check, I have a button to force GC. When I push that, I quickly get 6GB back. Doesn’t that prove my 6 arrays were not being referenced and COULD have been collected had the GC knew/wanted to? You are probably better off asking When does the GC automatically collect “garbage” memory?. Off … Read more
There is a recipe for sorting files larger than RAM on this page, though you’d have to adapt it for your case involving CSV-format data. There are also links to additional resources there. Edit: True, the file on disk is not “larger than RAM”, but the in-memory representation can easily become much larger than available … Read more
The getrusage library function returns a structure containing a whole lot of data about the current process, including these: long ru_ixrss; /* integral shared memory size */ long ru_idrss; /* integral unshared data size */ long ru_isrss; /* integral unshared stack size */ However, the most up-to-date linux documentation says about these 3 fields (unmaintained) … Read more
Mark Russinovich published a multipart series on windows memory resources really covers this very well. You can find it here: http://blogs.technet.com/b/markrussinovich/archive/2008/07/21/3092070.aspx He covers the reasons why the limits are what they are, as well as tests. The code for the tests are floating around in the tubes somewhere. If you want to know about memory … Read more
If you use fopen and fread instead of readfile, that should solve your problem. There’s a solution in the PHP’s readfile documentation showing how to use fread to do what you want.