Once we have our directory structure ready, let us understand a few coding conventions.
I know, but I am still learning the primitives myself: Also I think they guarantee byte accesses are atomic although not ordered which is why I went with "char" for my example Memory accesses can get reordered by the compiler or CPU.
The order in which system memory gets hit can be nothing like what you coded. The compiler and CPU will ensure such reorderings do not break single-threaded code. For single-threaded code, the memory model is irrelevant.
The old concept of sequence points has been discarded; the new standard specifies the same thing using a sequenced-before relation which is just a special case of the more general inter-thread happens-before concept.
The analogy is apt and has fundamental significance, but may be overkill for many people. However, I hope it provides a mental image a pictorial representation that facilitates reasoning about memory consistency models. The history of values held by each memory location is, therefore, represented by a vertical column at that memory address.
Each value change is due to one of the threads writing a new value to that location. Quoting from "A Primer on Memory Consistency and Cache Coherence" The intuitive and most restrictive memory model is sequential consistency SC in which a multithreaded execution should look like an interleaving of the sequential executions of each constituent thread, as if the threads were time-multiplexed on a single-core processor.
That global memory order can vary from one run of the program to another and may not be known beforehand. The characteristic feature of SC is the set of horizontal slices in the address-space-time diagram representing planes of simultaneity i.
On a given plane, all of its events or memory values are simultaneous. There is a notion of Absolute Time, in which all threads agree on which memory values are simultaneous.
In SC, at every time instant, there is only one memory image shared by all threads. That's, at every instant of time, all processors agree on the memory image i. Not only does this imply that all threads view the same sequence of values for all memory locations, but also that all processors observe the same combinations of values of all variables.
This is the same as saying all memory operations on all memory locations are observed in the same total order by all threads. In relaxed memory models, each thread will slice up address-space-time in its own way, the only restriction being that slices of each thread shall not cross each other because all threads must agree on the history of every individual memory location of course, slices of different threads may, and will, cross each other.
There is no universal way to slice it up no privileged foliation of address-space-time. Slices do not have to be planar or linear. They can be curved and this is what can make a thread read values written by another thread out of the order they were written in.
Histories of different memory locations may slide or get stretched arbitrarily relative to each other when viewed by any particular thread. Each thread will have a different sense of which events or, equivalently, memory values are simultaneous. The set of events or memory values that are simultaneous to one thread are not simultaneous to another.
Thus, in a relaxed memory model, all threads still observe the same history i. But they may observe different memory images i. Even if two different memory locations are written by the same thread in sequence, the two newly written values may be observed in different order by other threads.§1 Introduction.
Non-normative materials providing a context for the HTML specification. §2 Common infrastructure. The conformance classes, algorithms, definitions, and the common underpinnings of the rest of the specification.
However, not all of these elements require the end tag, or even the start tag, to be present. Some elements, the so-called void elements, do not have an end tag.A typical example is the (hard line-break) element.
is to use the backslash escape character. The backslash (\) escape character turns special characters into string characters: Strings Can be Objects.