Variable shared

Passive components (e.g., materials in storage tanks) can be described by shared variables denoted by Vi,..., vUv. The production and consumption of materials can be represented by actions, which either increase or decrease the value of the shared variables. The term shared refers to the fact that these variables can be manipulated by any automaton in the model. 

Actions Each action v =f(vi, V2, Vs,...) evaluates an arbitrary function / of shared variables and assigns the result to the variable vy... 

The considerations in the previous section about shared variables, automata, locations, transitions, enabling conditions and actions can be straightforwardly applied to the example process. It can be modeled by TA as shown in Figure 10.4. For the... 

More importantly, it is sometimes more informative. A very long nucleotide sequence may be required to provide more information than a restriction site survey. For example, a phylogenetic analysis of 22 taxa from the sunflower family used both restriction site variation in chloroplast DNA and nucleotide sequence variation in the chloroplast-encoded gene rbcL.5 The restriction site survey identified 583 variable sites of which 169 were shared between two or more taxa, whereas the sequence survey found only 109 shared variable positions. Even though the restriction site survey included only 11 enzymes, nearly 3500 nucleotides are included in the variable sequences surveyed, whereas rbcL is only 1428 base pairs (bp) in length. 

Figure 1.14 According to the anatomical variants of coronary circulation, there are areas of shared variable perfusion (A). The perfusion of these segments by the corresponding coronary arteries (B—D) can be seen in the bull s-eye images. For example, the apex (segment 17) is usually perfused by the LAD but sometimes by the RCA or even the LCX. Segments 3 and 9 are shared by LAD and RCA, and also small part of mid-low lateral wall is shared by LAD and LCX. Segments 4, 10 and 15 depend on the...

PCA has been often employed to explore the relationships among variables in a data set (19 20). Nevertheless, it is generally accepted that Factor Analysis (FA) is better suited than PCA to study these relationships (1 7). This is because FA algorithms are designed to distinguish between shared and unique variability. The shared variability, the so-called communalities in the FA community, reflect the common factors-common variability-among observable variables. The unique variability is only present in one observable variable. The common factors make up the relationship structure in the data. PCA makes no distinction between shared and unique variability and therefore it is not suited to find the structure in the data. 

Again, this is a very small model reflecting simple operator activity on one control via a review of two displays. However, it illustrates how large models of operator teams looking at numerous controls and manipulating many displays could be bmlt via the same building blocks used in this model. The central concepts of a task network and shared variable reflecting human-system dynamics remain the same. 

The flush directive is related to the volatile keyword in C/C++, although it is more flexible. A thread may create a temporary copy of a variable, for example, in a register, making it possible for different threads to have different values for a shared variable at the same time. Memory consistency is enforced when all threads needing a consistent copy of a variable encounter the flush directive. Specific variables can be named with the flush directive, or the variable names can be left out. In the latter case, all data visible to the thread is flushed. Below, the memory for x and y is flushed ... 

The shared clause explicitly specifies that the named variables will be shared among all threads. This is particularly useful when the default (none) clause is used (see the next section), in which case all shared variables declared in an outer scope must be explicitly named in a shared directive. 

The presence of shared variables makes VHDL-93 execution less deterministic. 

The point where the algorithm is altered is the loop iterating over the items. In this loop the main thread publishes its loop counter via a shared variable. The helper thread, by reading this variable (which, along with writing it, is an atomic operation on x86 architectuies), decides what item to preload. In order for the preexecution to be useful, we propose that a safe distance is always maintained between the threads. We call this distance jumpahead distance [19]. The value, however, cannot be a simple constant. It must reflect the characteristics of the system. 

Cache pollution is a concern. If the shared variables are changed by one thread executed on one of the physical cores the entire cache line must be immediately written to system memory and removed from the cache of every other core. We must assure that these writes do not pollute other variables which may reside in the same cache line as the shared variable. For this reason, the shared integer variables are each implemented as cache line-long byte arrays and are aligned on cache lines. 

Shared variable control. Read and update operations can be forced to either be performed directly to memory, or in a indivisible (atomic) manner. 

In order to reduce non-determinism and to increase the effectiveness of testing, non-preemptive execution is sometimes desirable (Bums 2001). The standard way of implementing many high-integrity applications is with a cyclic executive (Baker Shaw 1989). Using this technique a sequence of procedures is called within a defined time interval. Each procedure mns to completion and there is no concept of preemption. Data is passed from one procedure to another via shared variables and no synchronization constraints are needed, since the procedures never run concurrently. The major disadvantage with non-preemption is that it will usually (although not always) lead to reduced schedulability. 

Equation to Link Shared variables in MainReactor model with Kinetics model... 

Create kinetics connection Connection Type to share variables, parameters, and distribution domains across models with the same connection Connection Types Folder right click New Entity - Name kinetics connection. This connection needs to make accessible variable concentration c and reaction rate R. Since c and R are dependent on N and M parameters and xdomain distribution domain, they also need to be passed to the kinetics connection. The parameter diffusion length is also used in both submodels, MainReactor and Kinetics. Here, there are two options Either SET this parameter in the flow sheet model so that it will propagate to both submodels or SET it in one of the snbmodels and pass via the connection (the recommended option is used here as shown in Figure 9.18). 

Builds a binary tree, placing operators into the tree according to their degree of shared variable connectivity, with more connected operators closer to the root of the tree. Bottom-up tree traversal algorithms are used to cluster operators and values and perform fiinctional unit allocation and register allocation, respectively. A top-down tree traversal algorithm is used to assign interconnect. 

Shared variables must be used with caution to ensure that multiple assignments to the same variable in different processes are correctly synchronized. There must be no possibility that two processes could be updating the same variable concurrently. This can lead to a design with unpredictable (non-deterministic) simulation and synthesis results. 

A shared variable must be declared in the declarative part of the entity or architecture. It can be accessed by any process in the architecture. A variable must be declared inside a process and is only visible to that one process. 

When a branch condition is satisfied in the architecture CASEI, one of the input signals A, B, C or D is assigned directly to Y. In the architectures of Figure 4.6, two alternative method of assigning the output are demonstrated. In CASE2, a variable, TEMP, of type BIT has been declared. A private (non-shared) variable, declared within the process declarative part, is always local to the process. The value stored in TEMP after the Case statement has been evaluated must be assigned to Y inside die process. TEMP cannot be passed out of the process or accessed by any odier concurrent statement, such as another process. If the variable was shared (Qiapter 3)... 

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