The Newton method [
12,
13] refines an initial guess for solving a nonlinear problem by using a sequence of linear approximations. This technique, known for its rapid convergence—often quadratic—has been widely used since its development in the late 14th century to solve nonlinear equations. The fractional Newton method is an extension of the traditional Newton method, designed for nonlinear equations involving fractional derivatives. It incorporates fractional calculus operators, such as fractional integrals and derivatives, into the iterative process. This approach has demonstrated strong convergence properties and has been effective in solving complex nonlinear equations where other methods may fail. Several studies, including those by Torres-Hernandez et al. [
14], Akgül et al. [
15], Gajori et al. [
16], Kumar et al. [
17], and Candelario et al. [
18] describe a fractional version of the Newton technique with various fractional derivatives.
Based on both stability and efficiency, the method presented in [
19] is preferable to other well-known root-finding methods for nonlinear equations, such as those in [
20,
21,
22,
23] and the references cited therein. Nonlinear equations, particularly those involving fractional approaches, have gained significant attention due to their wide applications in addressing complex engineering problems. The numerical algorithm discussed exhibits local convergence in approximating simple solutions to fractional-order nonlinear problems. In addition to the basic iterative strategies for solving (
1) with integer or fractional convergence orders, there are parallel schemes with global convergence that can find all solutions to a nonlinear equation simultaneously. These schemes are more stable, consistent, and are particularly useful in parallel computing (see, e.g., [
24,
25,
26] and the references cited therein). However, a comprehensive literature review reveals that little work has focused on fractional-order numerical techniques for solving fractional nonlinear problems.
The primary goal of the current research is to enhance the convergence rate, stability, and accuracy of these parallel schemes. Challenges remain, particularly in ensuring efficient computation in higher dimensions. A comprehensive review of these trends, along with their limitations—such as handling fractional-order nonlinearities—provides context for the new numerical scheme. The proposed fractional family of parallel numerical schemes addresses several limitations of traditional iterative methods in the following ways:
On the other hand, when applied to nonlinear fractional-order differential equations with movable conditions, the method may exhibit slower convergence rates and higher computational demands. These challenges can introduce complex dynamics that might affect the overall effectiveness of the approach. Therefore, while the method is generally reliable, a careful analysis of the problem’s specific nature and conditions is essential to optimize its performance. In most cases, the method performs well, but in certain instances, additional strategies may be necessary to improve convergence and reduce computational costs.
Building on the method described in [
19], we consider the following fractional iterative scheme:
where
This method has a convergence order of 4 (abbreviated as M
[γ]), which satisfies the following error equation:
where
,
, and
The fractional version of this method is given by:
where
. We abbreviate this method as MM
[γ].
2.1. Convergence Analysis
For the iterative scheme given by Equation (
14), we establish the following theorem to determine its order of convergence.
Theorem 2. Letbe a continuous function, with of order m for any and containing the exact root ξ of . Furthermore, given a sufficiently close starting value , the convergence order of the Caputo-type fractional iterative schemeis least , with the error equation given by:where the constants are defined as follows: , ,
, ,
,
Here, and
Proof. Let
be a root of
ℏ and assume
. Using a Taylor series expansion of
and
around
and considering that
we obtain:
where
,
Thus, by multiplying Equations (
18) and (
20), we obtain
where
and
We have:
where
and
Thus,
where
where
Therefore,
where
where
where
,
,
,
,
,
Thus, the theorem is proven. □
2.2. Dynamical Analysis of the Fractional Scheme MMγ
Ensuring the robustness and reliability of solving nonlinear equations requires a careful examination of the dynamical behavior of solution techniques [
19]. Dynamical analysis in this context refers to a method’s ability to converge on the true root from an initial guess, even when there are small perturbations or errors in the calculations. Single root-finding algorithms generally have local convergence around the root, making them effective when the initial guess is close enough. However, their stability depends on the characteristics of the function and the initial approximation. If the function is poorly behaved or the initial guess is far from the root, these methods may diverge or converge to an incorrect solution.
The stability of a root-finding method can be analyzed using concepts from complex dynamical systems, which examine how sensitive the root is to variations in the input, as well as the convergence criterion, which evaluates how quickly the method approaches the root. The choice of parameters plays a crucial role in the method’s performance, particularly within the convergence zone (the red region) on the parametric plane. Stability and faster convergence are achieved when optimal parameters are selected from this region. However, choosing parameters near the boundary of this zone, or from the divergence zone, may lead to reduced stability or slower convergence rates. Selecting parameters from the divergence region can result in failure or divergence, as the method may become unstable. To mitigate the effects of computational errors and ensure reliable performance, stability is typically maintained by carefully balancing the method’s convergence properties with the appropriate selection of the initial guess, function parameters, and stopping criteria.
The following rational map
is obtained as:
where
For
, we have
where
,
,
,
and
a,
b belong to
Thus,
depends on
a,
b, and
x. Using the Möbius transformation
we see that
is conjugate with the operator, and for
we have [
19]
which is independent of
a and
b, as shown using Maple with 0 or
∞. Thus,
fits precisely with:
which exhibits interesting properties [
27].
Proposition 1. The fixed points of are as follows:
The stability function for
in the single root-finding method is given by:
For other values of the fractional parameter
, the stability regions are examined, as shown in
Figure 1a–c.
The stability region of the fractional iterative method MM
γ for finding the root of nonlinear equations illustrates the initial guesses or parameters for which the method converges to the correct root, as seen in
Figure 1a–c. The behavior in which the fractions contribute to assessing the method’s resilience and effectiveness in solving nonlinear equations under a range of
values is seen in
Figure 1a,c. The role of the fractional parameter
in determining the method’s stability and effectiveness is highlighted in these figures. The method is more stable when
, with stability decreasing as
approaches zero.
By using critical points as starting values, parametric planes are generated (see
Figure 2a–c), which depict the behavior of the method’s iterations, including patterns such as convergence, divergence, and chaotic behavior (
Figure 3a–h and
Figure 4a–c). These figures highlight stable and unstable behavior at various
values and
. In
Figure 2,
Figure 3 and
Figure 4, small circles represent fixed points, squares with stars indicate super-attracting fixed points, and squares denote critical points.
Parametric planes are essential for understanding the convergence behavior of iterative methods used to solve nonlinear equations. They provide insights into the stability and efficiency of iterations, helping to identify optimal parameters for fast and accurate convergence. These planes also reveal divergence zones, allowing for the avoidance of parameters that may cause instability or failure. By analyzing parametric planes, the optimal parameters for minimizing the number of iterations and improving solution reliability can be determined.
The figures also illustrate the method’s sensitivity to parameter changes, showing whether the approach is robust or requires careful tuning. Additionally, they display the nature of convergence—whether linear, super-linear, or quadratic—indicating how quickly the method reaches the solution. This information is crucial for selecting and optimizing parameters to ensure efficient and reliable problem-solving.
Understanding the dynamics of iterative methods is essential for solving nonlinear problems over time. Dynamic analysis helps evaluate how initial estimates affect outcomes, convergence rates, and overall stability. By analyzing these dynamics, one can ensure the reliability and efficiency of the approach, avoiding issues like slow convergence or divergence. In applied sciences and engineering, dynamic analysis plays a critical role in generating accurate solutions from iterative processes.
Dynamic planes offer insights into solution stability, convergence patterns, and behavior throughout the iterations. These planes reveal zones of attraction, where iterations converge, and regions of repulsion, where they diverge. They also highlight fixed points, cycles, and chaotic behavior, providing a deeper understanding of the methods’ sensitivity to initial conditions. This analysis is crucial for optimizing iterative methods and ensuring consistency in solving nonlinear equations. Similar to parametric planes, dynamic planes are generated to evaluate the stability of different schemes.
Figure 3a–h shows the stable behavior of the schemes for various values of
and
Choosing
values from the divergence zone of the parametric planes leads to unstable behavior, as illustrated in
Figure 4a,c for different
values.
Using the dynamical and parametric plane notation, we find the best parameter value that accelerates the rate of convergence of the simple root-finding method. Then, using the newly developed stable fractional-order scheme MM
γ as a correction factor, we propose a novel parallel fractional scheme for analyzing (
1) in the following section.