We study the nonlinear equations of the form \[x=\lambda D\left( x\right) +y,\] where \(\lambda \in \mathbb{R}\) and \(y\in E\) are fixed, and \(D:E\rightarrow E,\) with \(D\left( 0\right) =0\) a nonlinear mapping on the Banach space \(E\). We consider the iterative method \[\xi_{n+1}=\lambda D_{\varepsilon}\left( \xi_{n}\right) +y_{\varepsilon},\] where \(D_{\varepsilon}\) is an operator which approximates \(D\) and \(y_{\varepsilon}\) is an approximation for \(y\). We obtain an evaluation for \(\left \Vert \bar{x}-\xi_{n+1}\right \Vert \) in terms of \(\left \Vert D_{\varepsilon}\left( x\right) -D\left( x\right) \right \Vert \) and \(\left \Vert y-y_{\varepsilon}\right \Vert \).
Ion Păvăloiu
(Tiberiu Popoviciu Institute of Numerical Analysis)
Original title (in French)
Sur l’estimation des erreurs en convergence numérique de certaines méthodes d’iteration
English translation of the title
On the error estimation in the numerical convergence of certain iterative methods
nonlinear equation in Banach space; iterative method; error estimation
I. Păvăloiu, Sur l’estimation des erreurs en convergence numérique de certaines méthodes d’iteration, Seminar on functional analysis and numerical methods, Preprint no. 1 (1986), pp. 133-136 (in French).
[1] Babici, D.M., Ivanov, V.N., Otenca polnoi progresnosti prireshenia nelineinyh operatornyh uravnenii metodov prostei iteratii. Jurnal vycislitelnoi matematiki i matematiceskoi fisiki 7, 5 (1967), 988–1000.
[2] Pavaloiu, I., Introduction in the Theory of Approximating the Solutions of Equations, Ed. Dacia 1976 (in Romanian).
[3] Urabe, M., Error estimation in numerical solution of equations by iteration process, J. Sci. Hiroshima Univ. Ser. A-I, 26 (1962), 77–91
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Sur l’estimation des erreurs en convergence numérique de certaines méthodes d’itération (English translation) On the estimation of errors in numerical convergence of certain iteration methods
"Babeş-Bolyai" University
Faculty of Mathematics and Physics
Seminar on Functional Analysis and Numerical Methods
Preprint nr.1, 1986, pp.133-136
Sur l’estimation des erreurs en convergence numérique de certaines méthodes d’itération
(English translation)
On the estimation of errors in numerical convergence of certain iteration methods
Ion Păvăloiu
Let be a Banach space and
an operatorial equation, where and is the null element of the space
In order to solve equation (1) we consider the following iterative
process:
| (2) |
|
|
|
We denote by the ball of
radius and center .
Regarding the convergence of iterations (2) we shall consider the
following theorem
Theorem 1.
If the application and the element from equation
(1) verify the following conditions:
-
i.
for
all where is a functional;
-
ii.
-
iii.
then equation (1) admits a unique solution
This solution is obtained as the limit of the sequence generated by method (2), and the following
estimation holds:
| (3) |
|
|
|
Let be an application which verifies the conditions:
-
i
where and
-
ii
for every where
-
iii
whereand
-
iv
We consider an element for which
whereand
In order to solve equation (1) we consider, instead of iterative
method (2) the following iterative procedure:
| (4) |
|
|
|
Regarding the convergence of method (4) we obtain the following theorem:
Theorem 2.
If the conditions of Theorem 1 are
fulfilled, the operator and the element
verify conditions – and if
then there exists an so that for all we have
| (6) |
|
|
|
and
Proof.
Indeed, from the fact that and it follows that there exists a number so that for we have
|
|
|
and
|
|
|
|
|
|
|
|
for because for and
as .
If we take now
then the theorem is proved.
∎
Relations (6) and (7) assure the convergence of sequence
determined by method (4).
We show now that in the conditions of Theorem 2 we have the
following estimation:
| (8) |
|
|
|
Indeed, we have
|
|
|
|
|
|
|
|
so inequality (8) follows. From (8) it results
|
|
|
where
References
-
[1]
-
[2]
Babici, D.M., Ivanov, V.N., Oţenca polnoi
progresnosti prireshenia nelineinyh operatornyh uravnenii metodov prostei
iteraţii. Jurnal vycislitelnoi matematiki i matematiceskoi fisiki 7, 5 (1967),
988–1000.
-
[3]
Păvăloiu, I.,
††margin:
clickable
Introduction in the Theory of
Approximating the Solutions of Equations, Ed. Dacia 1976 (in Romanian).
-
[4]
Urabe, M., Error estimation in numerical solution of equations by
iteration process, J. Sci. Hiroshima Univ. Ser. A-I, 26 (1962), 77–91.