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There are three reasons for the atomicity requirements. First, a reference count field may be updated by multiple threads, and so an adequate atomic instruction, such as a (costly) compare-and-swap, must be used to update the counts. Second, it must be clear which object loses a reference so that its reference count can be adequately decremented.
The atomic counter and atomic bitmask operations in the Linux kernel typically use a compare-and-swap instruction in their implementation. The SPARC-V8 and PA-RISC architectures are two of the very few recent architectures that do not support CAS in hardware; the Linux port to these architectures uses a spinlock. [7]
For example, in base 2, the counter can estimate the count to be 1, 2, 4, 8, 16, 32, and all of the powers of two. The memory requirement is simply to hold the exponent. As an example, to increment from 4 to 8, a pseudo-random number would be generated such that the probability the counter is increased is 0.25. Otherwise, the counter remains at 4.
Atomic operations Shared data is accessed by using atomic operations which cannot be interrupted by other threads. This usually requires using special machine language instructions, which might be available in a runtime library. Since the operations are atomic, the shared data is always kept in a valid state, no matter how other threads access it.
A time-interval counter is being used to measure the time between the rising edge of the reference (channel A) and the rising edge of the device under test. In order to provide evenly spaced measurements, the reference clock will be divided down to form the measurement rate, triggering the time-interval counter (ARM input).
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A counting Bloom filter is a probabilistic data structure that is used to test whether the number of occurrences of a given element in a sequence exceeds a given threshold. As a generalized form of the Bloom filter, false positive matches are possible, but false negatives are not – in other words, a query returns either "possibly bigger or equal than the threshold" or "definitely smaller ...
In this scenario, the front desk count-holder represents a counting semaphore, the rooms are the resource, and the students represent processes/threads. The value of the semaphore in this scenario is initially 10, with all rooms empty. When a student requests a room, they are granted access, and the value of the semaphore is changed to 9.