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Tarjan's strongly connected components algorithm is an algorithm in graph theory for finding the strongly connected components (SCCs) of a directed graph. It runs in linear time , matching the time bound for alternative methods including Kosaraju's algorithm and the path-based strong component algorithm .
In order to fully utilize the bandwidth of different types of memory such as caches and memory banks, few compilers or CPU architectures ensure perfectly strong ordering. [1] [5] Among the commonly used architectures, x86-64 processors have the strongest memory order, but may still defer memory store instructions until after memory load ...
However, on the 80386, with its paged memory management unit it is possible to protect individual memory pages against writing. [4] [5] Memory models are not limited to 16-bit programs. It is possible to use segmentation in 32-bit protected mode as well (resulting in 48-bit pointers) and there exist C language compilers which support that. [6]
The memory model stipulates that changes to the values of shared variables only need to be made visible to other threads when such a synchronization barrier is reached. Moreover, the entire notion of a race condition is defined over the order of operations with respect to these memory barriers. [1]
In order to reduce the prediction latency, Jimenez proposed in 2003 the fast-path neural predictor, where the perceptron predictor chooses its weights according to the current branch's path, rather than according to the branch's PC. Many other researchers developed this concept (A. Seznec, M. Monchiero, D. Tarjan & K. Skadron, V. Desmet, Akkary ...
Program order guarantees that each process issues a memory request ordered by its program and write atomicity defines that memory requests are serviced based on the order of a single FIFO queue. In relaxing program order, any or all the ordering of operation pairs, write-after-write, read-after-write, or read/write-after-read, can be relaxed.
Memory hierarchy of an AMD Bulldozer server. The number of levels in the memory hierarchy and the performance at each level has increased over time. The type of memory or storage components also change historically. [6] For example, the memory hierarchy of an Intel Haswell Mobile [7] processor circa 2013 is:
The following multi-threaded program, running on a multi-core processor gives an example of how such out-of-order execution can affect program behavior: Initially, memory locations x and f both hold the value 0. The software thread running on processor #1 loops while the value of f is zero, then it prints the value of x.