memory - Read For Learn

Difference between word addressable and byte addressable

A byte is a memory unit for storage A memory chip is full of such bytes. Memory units are addressable. That is the only way we can use memory. In reality, memory is only byte addressable. It means: A binary address always points to a single byte only. A word is just a group of bytes – 2, 4, 8 depending upon the data bus size of the CPU. To understand the memory operation fully, you must be familiar with the various registers of the CPU and the memory ports of the RAM. I assume … Read more

How do I profile memory usage in Python?

This one has been answered already here: Python memory profiler Basically you do something like that (cited from Guppy-PE):

In Python, what is `sys.maxsize`?

Python can handle arbitrarily large integers in computation. Any integer too big to fit in 64 bits (or whatever the underlying hardware limit is) is handled in software. For that reason, Python 3 doesn’t have a sys.maxint constant. The value sys.maxsize, on the other hand, reports the platform’s pointer size, and that limits the size of Python’s data … Read more

memory error in python

This one here: seems to be very inefficient and expensive for large strings. Better do A buffer object keeps a reference to the original string and start and length attributes. This way, no unnecessary duplication of data occurs. A string of length l has l*l/2 sub strings of average length l/2, so the memory consumption would roughly be l*l*l/4. With a … Read more

Using Dynamic Memory allocation for arrays

You use pointers. Specifically, you use a pointer to an address, and using a standard c library function calls, you ask the operating system to expand the heap to allow you to store what you need to. Now, it might refuse, which you will need to handle. The next question becomes – how do you … Read more

What does ** do in C language?

In C arguments are passed by values. For example if you have an integer varaible in main and the following function then if you call the function in main like this then the parameter gets the value of variable x in main. However the parameter itself occupies a different extent in memory than the argument. So any … Read more

Python subprocess.Popen “OSError: [Errno 12] Cannot allocate memory”

As a general rule (i.e. in vanilla kernels), fork/clone failures with ENOMEM occur specifically because of either an honest to God out-of-memory condition (dup_mm, dup_task_struct, alloc_pid, mpol_dup, mm_init etc. croak), or because security_vm_enough_memory_mm failed you while enforcing the overcommit policy. Start by checking the vmsize of the process that failed to fork, at the time of the fork attempt, and then compare to the amount of free memory (physical and swap) as it … Read more

How does the “view” method work in PyTorch?

The view function is meant to reshape the tensor. Say you have a tensor a is a tensor that has 16 elements from 1 to 16(included). If you want to reshape this tensor to make it a 4 x 4 tensor then you can use Now a will be a 4 x 4 tensor. Note that after the reshape the total number of … Read more

How to clear variables in ipython?

%reset seems to clear defined variables.

How to solve munmap_chunk(): invalid pointer error in C++

This happens when the pointer passed to free() is not valid or has been modified somehow. I don’t really know the details here. The bottom line is that the pointer passed to free() must be the same as returned by malloc(), realloc() and their friends. It’s not always easy to spot what the problem is for a novice in their own code … Read more

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