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    MPI
    OpenMP
Virtual Memory
    Naive (Old) Model
        Copy entire Programmers Model, store in RAM
        Problems
            unable to grow processes
            fragmentation / loss of space
            no checks for overwriting processes
            no space / system for extra processes - (esentially use DMTCP)
    Relative Addresses - Basic Solution
        Registers
            Base Register - starts at top of the text - always added to the offset
            Bound Register - the size of the region - prevents overwriting
        creates relative addresses that are easy to address and calculate
    Address Space - the memory region of a process
        Virtual Address Space - given the whole memory size minus the OS (Ex: 1GB)
        Physical Address Space - the size of the RAM
    Paging - avoiding fragmentation
        Possible Approaches
            Put each region in its own section - not good enough
            divide into very small pieces (4KB) - good enough, but we need to implement this
                no base address for processes anymore
    Page Tables
        Summary
            Each Virtual Address is translated into a page number or set of numbers and an offset
            Available for each process
        Example: 0x00410123
            Page #: 0x00410
            Offset: 123 - max size of the hex number = the size of the page
        Problem
            1 Million Pages with 4GB VA size
            Size Per Page Table Entry: 8
            Page Tables Cumulative Size: 8 Million (per process)
            200 Processes -> 1.6GB for storage of page tables - way too much
            Not scalable to even be feasible with 64 bit system
        Solution
            Multiple levels of paging