Arithmetic operation on very large static arrays in C/C++
arrays, c, c++, stack, static
Solution
Local variables will always be on the stack, no matter optimization flags. And that array will be around 7 gigabyte! Way larger than any possible stack.
The size may also be a reason it doesn't start, as if you put it as a global/static variable then you need to have more than 7 GB or virtual memory free and contiguous to be able to even load the program.
Problem
I am new to `High Performance Computing` and my first question in this forum where I have been a reader for much long. Basically I need to do arithmetic operations on very large arrays like for instance ``` double variable [9][4][300][300][300] (uninitialized) ``` case 1: If I declare the array above as `local/automatic` then I get run-time error if I had compiled without optimization like "`g++ file.cpp`" .. (the error is segmentation fault -- stack overflow???) case 2: In the same case as above if I had compile with optimization the code runs as expected. `"g++ -O2 file.cp`p" (is the `array` in `bss` now???) case 3: If I make the variable `global/static` then it compiles fine but nonetheless it does not run and just gives a message "`killed`" on terminal and terminates. There is no real problem but I am curious and want to learn what happens when extremely large arrays are declared and where do they reside in memory depending on their data type. I am also aware of the method of generating these arrays at run-time using malloc or new. Then of course it would be on heap. So the most important question for me is --> which is the most efficient method (i.e. smallest run-time during computation of arrays in memory) of dealing with large arrays when compiling with `g++` and running on `linux clusters`. Thank you for your patience for reading.