Non-recursive Filter Example: y[n] = 0.5x[n − 1] + 0.5x[n]. Recursive Filter Example: y[n] = 0.5y[n − 1] + 0.5x[n].
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Recursive algorithms can be replaced with non-recursive counterparts. One method for replacing recursive algorithms is to simulate them using heap memory in place of stack memory. An alternative is to develop a replacement algorithm entirely based on non-recursive methods, which can be challenging. For example, recursive algorithms for matching wildcards, such as Rich Salz' wildmat algorithm, were once typical.
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A non-recursive grammar can produce only a finite language; and each finite language can be produced by a non-recursive grammar. For example, a straight- line grammar produces just a single word. A recursive context-free grammar that contains no useless rules necessarily produces an infinite language. This property forms the basis for an algorithm that can test efficiently whether a context-free grammar produces a finite or infinite language..
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In computer (software) technology, a wildcard is a symbol used to replace or represent one or more characters. Algorithms for matching wildcards have been developed in a number of recursive and non-recursive varieties.
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Early algorithms for matching wildcards often relied on recursion, but the technique was criticized on grounds of performance and reliability considerations. Non-recursive algorithms for matching wildcards have gained favor in light of these considerations. Among both recursive and non-recursive algorithms, strategies for performing the pattern matching operation vary widely, as evidenced among the variety of example algorithms referenced below. Test case development and performance optimization techniques have been demonstrably brought to bear on certain algorithms, particularly those developed by critics of the recursive algorithms.
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Non-recursive algorithms for the same purpose, such as the Krauss matching wildcards algorithm, have been developed to avoid the drawbacks of recursion and have improved only gradually based on techniques such as collecting tests and profiling performance.
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Scaling law is likely to replace Töpfer's radical law to be a universal law for various mapping practices. What underlies scaling law is something of paradigm shift from Euclidean geometry to fractal, from non-recursive thinking to recursive thinking.
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Plan 9's union directory architecture inspired 4.4BSD and Linux union file system implementations, although the developers of the BSD union mounting facility found the non-recursive merging of directories in Plan 9 "too restrictive for general purpose use".
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Theoretical bit-error rate curves of encoded QPSK (recursive and non-recursive, soft decision), additive white Gaussian noise channel. Curves are small distinguished due to approximately the same free distances and weights. The free distanceMoon, Todd K. "Error correction coding." Mathematical Methods and Algorithms.
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The encoder on the picture above is a non-recursive encoder. Here's an example of a recursive one and as such it admits a feedback structure: Img.2. Rate 1/2 8-state recursive systematic convolutional encoder. Used as constituent code in 3GPP 25.212 Turbo Code.
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Recursive and non-recursive convolutional codes are not so much different in BER performance, however, recursive type of is implemented in Turbo convolutional codes due to better interleaving properties.Benedetto, Sergio, and Guido Montorsi. "Role of recursive convolutional codes in turbo codes." Electronics Letters 31.11 (1995): 858-859.
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A resolution process may use a combination of these methods. In a non-recursive query, a DNS resolver queries a DNS server that provides a record either for which the server is authoritative, or it provides a partial result without querying other servers. In case of a caching DNS resolver, the non-recursive query of its local DNS cache delivers a result and reduces the load on upstream DNS servers by caching DNS resource records for a period of time after an initial response from upstream DNS servers. In a recursive query, a DNS resolver queries a single DNS server, which may in turn query other DNS servers on behalf of the requester.
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In computer science, the Krauss wildcard-matching algorithm is a pattern matching algorithm. Based on the wildcard syntax in common use, e.g. in the Microsoft Windows command-line interface, the algorithm provides a non- recursive mechanism for matching patterns in software applications, based on syntax simpler than that typically offered by regular expressions.
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This non-recursive implementation is similar to the non-recursive implementation of depth-first search, but differs from it in two ways: # it uses a queue (First In First Out) instead of a stack and # it checks whether a vertex has been discovered before enqueueing the vertex rather than delaying this check until the vertex is dequeued from the queue. If is a tree, replacing the queue of this breadth- first search algorithm with a stack will yield a depth-first search algorithm. For general graphs, replacing the stack of the iterative depth-first search implementation with a queue would also produce a breadth-first search algorithm, although a somewhat nonstandard one. The Q queue contains the frontier along which the algorithm is currently searching.
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In X-bar theory in linguistics, specifiers, head words, complements and adjuncts together form phrases. Specifiers differ from complements and adjuncts because they are non-recursive, and phrases can only have one specifier. They are not sisters of the head, but rather sisters of the phrase formed by the head and the complement or adjunct.
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The example encoder is systematic because the input data is also used in the output symbols (Output 2). Codes with output symbols that do not include the input data are called non- systematic. Recursive codes are typically systematic and, conversely, non- recursive codes are typically non-systematic. It isn't a strict requirement, but a common practice.
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The client side of the DNS is called a DNS resolver. A resolver is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address. DNS resolvers are classified by a variety of query methods, such as recursive, non- recursive, and iterative.
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Notable among them was Micro-SPL, a version written for the Xerox Alto workstation. This machine had originally used BCPL as its primary language, but dissatisfaction with its performance led Henry Baker to design a non-recursive language that he implemented with Clinton Parker in 1979. Clinton would then further modify Micro-SPL to produce Action! for the Atari 8-bit family in 1983.
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Then, the second phase was a rapid Chomskian Single Step, consisting of three distinct events that happened in quick succession around 70,000 years ago and allowed for the shift from non-recursive to recursive language in early hominins. # A genetic mutation that slowed down the Prefrontal Synthesis (PFS) critical period of at least two children that lived together; # This allowed these children to create recursive elements of language such as spatial prepositions; # Then this merged with their parent's non-recursive language to create recursive language. It is not enough for children to have a modern Prefrontal Cortex (PFC) to allow for the development of PFS, the children must also be mentally stimulated and have recursive elements already in their language to acquire PFS. Since, their parents would not have invented these elements yet, the children would have had to do it themselves, which is a common occurrence among young children that live together, in a process called cryptophasia.
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This has the effect of complicating the design problem and also limiting the number of practical implementations. Digital filters can be categorized into two main types, namely finite impulse response (FIR) and infinite impulse response (IIR). 2-D FIR digital filter is achieved by a non-recursive algorithm structure while 2-D IIR digital filter is achieved by a recursive feedback algorithm structure.T. S. Huang, “Stability of two-dimensional recursive filters,” IEEE Transactions on Audio and Electroacoustics, vol.
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Thus this code number of a proof of contradiction of T must be a non-standard number. In fact, the model of any theory containing PA obtained by the systematic construction of the arithmetical model existence theorem, is always non-standard with a non-equivalent provability predicate and a non-equivalent way to interpret its own construction, so that this construction is non- recursive (as recursive definitions would be unambiguous). Also, there is no recursive non-standard model of PA.
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A multiplicative scrambler used in V.34 recommendation A multiplicative descrambler used in V.34 recommendation Multiplicative scramblers (also known as feed-through) are called so because they perform a multiplication of the input signal by the scrambler's transfer function in Z-space. They are discrete linear time- invariant systems. A multiplicative scrambler is recursive, and a multiplicative descrambler is non-recursive. Unlike additive scramblers, multiplicative scramblers do not need the frame synchronization, that is why they are also called self-synchronizing.
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A computational model going beyond Turing machines was introduced by Alan Turing in his 1938 PhD dissertation Systems of Logic Based on Ordinals.Alan Turing, 1939, Systems of Logic Based on Ordinals Proceedings London Mathematical Society Volumes 2–45, Issue 1, pp. 161–228. This paper investigated mathematical systems in which an oracle was available, which could compute a single arbitrary (non-recursive) function from naturals to naturals. He used this device to prove that even in those more powerful systems, undecidability is still present.
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The Lock Service is a distributed lock service, which is intended for use in a cluster where processes in different nodes might compete with each other for access to a shared resource. For them, the Lock Service provides entities called lock resources, which in turn, application processes use to coordinate access to those shared resources. The Lock Service provides a simple lock model supporting one locking mode for exclusive access and another one for shared access. The locks provided by the Lock Service are non-recursive.
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As block sort is non-recursive and does not require the use of dynamic allocations, this leads to constant stack and heap space. It uses O(1) auxiliary memory in a transdichotomous model, which accepts that the O(log n) bits needed to keep track of the ranges for A and B cannot be any greater than 32 or 64 on 32-bit or 64-bit computing systems, respectively, and therefore simplifies to O(1) space for any array that can feasibly be allocated.
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Divide-and-conquer algorithms can also be implemented by a non-recursive program that stores the partial sub-problems in some explicit data structure, such as a stack, queue, or priority queue. This approach allows more freedom in the choice of the sub-problem that is to be solved next, a feature that is important in some applications — e.g. in breadth-first recursion and the branch-and-bound method for function optimization. This approach is also the standard solution in programming languages that do not provide support for recursive procedures.
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In 1970, E.F. Codd proposed the relational data model, now widely accepted as the standard data model. At that time, office automation was the major use of data storage systems, which resulted in the proposal of many NF2 data models like the Schek model, Jaeschke models (Non-recursive and recursive algebra), and the Nested Table Data (NTD) model. IBM organized the first international workshop exclusively on this topic in 1987 which was held in Darmstadt, Germany. Moreover, a lot of research has been done and journals have been published to address the shortcomings of the relational model.
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As this is a non-recursive method for traversal, it has to be an iterative procedure; meaning, all the steps for the traversal of a node have to be under a loop so that the same can be applied to all the nodes in the tree. We will consider the IN-ORDER traversal again. Here, for every node, we'll visit the left sub-tree (if it exists) first (if and only if we haven't visited it earlier); then we visit (i.e. print its value, in our case) the node itself and then the right sub-tree (if it exists).
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As a final case, if the first character of the string is equal to the character of the current node then the function returns the node if there are no more characters in the key. If there are more characters in the key then the first character of the key must be removed and a recursive call is made given the equal kid node and the modified key. This can also be written in a non-recursive way by using a pointer to the current node and a pointer to the current character of the key.
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The Ultraspherical window's µ parameter determines whether its Fourier transform's side-lobe amplitudes decrease, are level, or (shown here) increase with frequency. The Ultraspherical window was introduced in 1984 by Roy Streit and has application in antenna array design, non-recursive filter design, and spectrum analysis. Like other adjustable windows, the Ultraspherical window has parameters that can be used to control its Fourier transform main-lobe width and relative side-lobe amplitude. Uncommon to other windows, it has an additional parameter which can be used to set the rate at which side-lobes decrease (or increase) in amplitude.
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Windowing is a process where an index limited sequence has its maximum energy concentrated in a finite frequency interval. This can be extended to an N-dimension where the N-D window has the limited support and maximum concentration of energy in a separable or non-separable N-D passband. The design of an N-dimensional window particularly a 2-D window finds applications in various fields such as spectral estimation of multidimensional signals, design of circularly symmetric and quadrantally symmetric non-recursive 2D filters, design of optimal convolution functions, image enhancement so as to reduce the effects of data-dependent processing artifacts, optical apodization and antenna array design.
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In pseudocode, the pairwise summation algorithm for an array of length > 0 can be written: s = pairwise(x[1…n]) if n ≤ N base case: naive summation for a sufficiently small array s = x[1] for i = 2 to n s = s + x[i] else divide and conquer: recursively sum two halves of the array m = floor(n / 2) s = pairwise(x[1…m]) + pairwise(x[m+1…n]) end if The non-recursive version of the algorithm uses a stack to accumulate partial sums: partials = new Stack for i = 1 to n partials.push(x[i]) j = i while is_even(j) j = floor(j / 2) p = partials.pop() q = partials.pop() partials.
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The triggers that induce the catharsis of a crisis often coincide with and are undistinguishable from the triggers launching qualitative transformations of the economy, business and society at large. While crises are cyclical recessions or slowdowns within the same paradigm, transformation represents a paradigmatic change in the way of doing business: moving towards new standards and quality, in a unique and non-recursive way. Most developed and mature economies of the world (USA, Japan, Western Europe) are undergoing long-term transformation towards a “new normal” of doing business, state governance and ways of life. Cyclical crisis is a parallel, accompanying phenomenon, subject to different causes, special rules and separate dynamics.
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Research on the inductive synthesis of recursive functional programs started in the early 1970s and was brought onto firm theoretical foundations with the seminal THESIS system of Summers and work of Biermann. These approaches were split into two phases: first, input-output examples are transformed into non- recursive programs (traces) using a small set of basic operators; second, regularities in the traces are searched for and used to fold them into a recursive program. The main results until the mid 1980s are surveyed by Smith. Due to limited progress with respect to the range of programs that could be synthesized, research activities decreased significantly in the next decade.
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For example, a simple stub resolver running on a home router typically makes a recursive query to the DNS server run by the user's ISP. A recursive query is one for which the DNS server answers the query completely by querying other name servers as needed. In typical operation, a client issues a recursive query to a caching recursive DNS server, which subsequently issues non-recursive queries to determine the answer and send a single answer back to the client. The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in the query headers.
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In computer science, a recursive descent parser is a kind of top-down parser built from a set of mutually recursive procedures (or a non-recursive equivalent) where each such procedure implements one of the nonterminals of the grammar. Thus the structure of the resulting program closely mirrors that of the grammar it recognizes. A predictive parser is a recursive descent parser that does not require backtracking. Predictive parsing is possible only for the class of LL(k) grammars, which are the context-free grammars for which there exists some positive integer k that allows a recursive descent parser to decide which production to use by examining only the next k tokens of input.
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As a consequence, at the "external/first-merge-only" stage, young children would show an inability to interpret readings from a given ordered pair, since they would only have access to the mental parsing of a non-recursive set. (See Roeper for a full discussion of recursion in child language acquisition).). In addition to word-order violations, other more ubiquitous results of a first-merge stage would show that children's initial utterances lack the recursive properties of inflectional morphology, yielding a strict Non-inflectional stage-1, consistent with an incremental Structure- building model of child language. Generative grammar, associated especially with the work of Noam Chomsky, is currently one of the approaches to explaining children's acquisition of syntax.
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This strategy avoids the overhead of recursive calls that do little or no work, and may also allow the use of specialized non-recursive algorithms that, for those base cases, are more efficient than explicit recursion. A general procedure for a simple hybrid recursive algorithm is short-circuiting the base case, also known as arm's-length recursion. In this case whether the next step will result in the base case is checked before the function call, avoiding an unnecessary function call. For example, in a tree, rather than recursing to a child node and then checking whether it is null, checking null before recursing; this avoids half the function calls in some algorithms on binary trees.
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When the shared resource must be reserved without blocking all other tasks (such as waiting for Flash memory to be written), it is better to use mechanisms also available on general- purpose operating systems, such as a mutex and OS-supervised interprocess messaging. Such mechanisms involve system calls, and usually invoke the OS's dispatcher code on exit, so they typically take hundreds of CPU instructions to execute, while masking interrupts may take as few as one instruction on some processors. A (non-recursive) mutex is either locked or unlocked. When a task has locked the mutex, all other tasks must wait for the mutex to be unlocked by its owner - the original thread.
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The algorithm is based on a history of development, correctness and performance testing, and programmer feedback that began with an unsuccessful search for a reliable non-recursive algorithm for matching wildcards. An initial algorithm, implemented in a single while loop, quickly prompted comments from software developers, leading to improvements. Ongoing comments and suggestions culminated in a revised algorithm still implemented in a single while loop but refined based on a collection of test cases and a performance profiler. The experience tuning the single while loop using the profiler prompted development of a two-loop strategy that achieved further performance gains, particularly in situations involving empty input strings or input containing no wildcard characters.
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Philosophers have interpreted the Church–Turing thesis as having implications for the philosophy of mind.For a good place to encounter original papers see B. Jack Copeland states that it is an open empirical question whether there are actual deterministic physical processes that, in the long run, elude simulation by a Turing machine; furthermore, he states that it is an open empirical question whether any such processes are involved in the working of the human brain. There are also some important open questions which cover the relationship between the Church–Turing thesis and physics, and the possibility of hypercomputation. When applied to physics, the thesis has several possible meanings: #The universe is equivalent to a Turing machine; thus, computing non-recursive functions is physically impossible.
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For non-recursive function calls, this is usually an optimization that saves only a little time and space, since there are not that many different functions available to call. When dealing with recursive or mutually recursive functions where recursion happens through tail calls, however, the stack space and the number of returns saved can grow to be very significant, since a function can call itself, directly or indirectly, creating a new call stack frame each time. Tail call elimination often reduces asymptotic stack space requirements from linear, or O(n), to constant, or O(1). Tail call elimination is thus required by the standard definitions of some programming languages, such as Scheme, and languages in the ML family among others.
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In general, insertion sort will write to the array O(n2) times, whereas selection sort will write only O() times. For this reason selection sort may be preferable in cases where writing to memory is significantly more expensive than reading, such as with EEPROM or flash memory. While some divide-and-conquer algorithms such as quicksort and mergesort outperform insertion sort for larger arrays, non-recursive sorting algorithms such as insertion sort or selection sort are generally faster for very small arrays (the exact size varies by environment and implementation, but is typically between 7 and 50 elements). Therefore, a useful optimization in the implementation of those algorithms is a hybrid approach, using the simpler algorithm when the array has been divided to a small size.
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Early algorithms for matching wildcards, such as Rich Salz' wildmat algorithm, typically relied on recursion, a technique criticized on grounds of performance. The Krauss matching wildcards algorithm was developed based on an attempt to formulate a non-recursive alternative using test cases followed by optimizations suggested via performance profiling, resulting in a new algorithmic strategy conceived in light of the profiling along with other considerations. Profilers that collect data at the level of basic blocks If, on the other hand, you need to step through your code with microscopic accuracy, fine-tuning individual machine instructions, then an active profiler with cycle-counting cannot be beat. or that rely on hardware assistance provide results that can be accurate enough to assist software developers in optimizing algorithms for a particular computer or situation.
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In computer science, a grammar is informally called a recursive grammar if it contains production rules that are recursive, meaning that expanding a non- terminal according to these rules can eventually lead to a string that includes the same non-terminal again. Otherwise it is called a non-recursive grammar.. For example, a grammar for a context-free language is left recursive if there exists a non-terminal symbol A that can be put through the production rules to produce a string with A (as the leftmost symbol). Notes on Formal Language Theory and Parsing, James Power, Department of Computer Science National University of Ireland, Maynooth Maynooth, Co. Kildare, Ireland.. All types of grammars in the Chomsky hierarchy can be recursive and it is recursion that allows the production of infinite sets of words.
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