Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 92 This work is licensed under a Creative Commons Attribution 4.0 International License. The Implementations Special Third-Order Ordinary Differential Equations (ODE) for 5th-order 3rd-stage Diagonally Implicit Type Runge- Kutta Method (DITRKM) Department of Mathematics, Facultyof Computer Sciences and Mathematics,Tikrit University, Iraq. Abstract The derivation of 5th order diagonal implicit type Runge Kutta methods (DITRKM5) for solving 3rd special order ordinary differential equations (ODEs) is introduced in the present study. The DITRKM5 techniques are the name of the approach. This approach has three equivalent non-zero diagonal elements. To investigate the current study, a variety of tests for five various initial value problems (IVPs) with different step sizes h were implemented. Then, a comparison was made with the methods indicated in the other literature of the implicit RK techniques. The numerical techniques are elucidated as the qualification regarding the efficiency and number of function evaluations compared with another literature of the implicit RK approaches from the result of the computations. In addition, the stability polynomial for DITRK method is derived and analyzed. Keywords: Numerical Methods, Ordinary Differential Equations, Diagonal Implicit Type Runge Kutta Methods, Initial Value Problems, Stability Polynomial Analysis. 1. Introduction Third-order ODEs are used in neural network engineering and applied sciences, the dynamics of fluid flow, the ship's motion, and electric circuits, among other fields [1-6]. Consider the numerical method for solving the special "initial value problems" (IVPs) for order three as the following form ๐‘ฆโ€ฒโ€ฒโ€ฒ(๐‘ฅ) = ๐‘“(๐‘ฅ, ๐‘ฆ(๐‘ฅ)) (2.1) ๐‘ฆ(๐‘ฅ0) = ๐›ผ, ๐‘ฆ โ€ฒ(๐‘ฅ0) = ๐›ฝ and ๐‘ฆ โ€ฒโ€ฒ(๐‘ฅ0) = ๐›พ Ibn Al Haitham Journal for Pure and Applied Science Journal homepage: http://jih.uobaghdad.edu.iq/index.php/j/index Doi: 10.30526/35.1.2803 Article history: Received 29 August, 2021, Accepted 26, September, 2021, Published in January 2022. Firas A. Fawzi firasadil01@gmail.com Mustafa H. Jumaa mustafa.hassan551991@gmail.com https://creativecommons.org/licenses/by/4.0/ mailto:firasadil01@gmail.com mailto:mustafa.hassan551991@gmail.com Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 93 The implicit methods are important because they can reach high orders of accuracy at the equivalent number of stages, which can be represented as an advantage that leads to the more accurate than the explicit approaches. This manufactures it easier to exist the solution to the difficulties of the problems. So, the implicit RK techniques play an important role for denomination the physical and mathematical problems, like a differential algebraic equation. In addition, diagonal implicit RK (DIRK) techniques are also pointed to as semi-implicit approaches or semi explicit RK techniques since they obtained at minimum one value does not zero for the lower of the triangular diagonal matrices. Therefore, to solve Eq. (2.1), two general strategies can be employed. The elementary way is to transfer the Eq. (2.1) into a problem with first-order then apply any pattern of the RK approach to it. As a result, numerous implicit RK approaches, such as Ismail et al. [7] and others, have been developed. The second option is to use the RK Type method to directly solve Eq. (2.1). For second-order systems, several scholars provided an efficient implicit RK technique (see [8-13]). Ghawadri et al. [14], constructed a solution to the ill-posed issue for a beam with an elastically base using special fourth-order ODEs. Moreover, [15-17] developed a solution of the special 3rd order for the ODEs directly by RK technique. Finally, Senu [18] and Fawzi et al. [19] constructed the embedded the RK technique to solve 3rd order for the ODEs. A significant objective for current research is to show how particular third-order ODEs are solving via the DIRECT method. Additionally, while solving eq. (2.1) numerically, the algebraic order of the technique used must be taken into account, as this is the most important factor in achieving high accuracy. Section 2.2 demonstrates the basic idea of construction and derivation of the DITRK system for addressing Initial Value Problems (IVPs). The DITRK technique's order criteria are outlined in Section 2.3. Section 2.4 describes the 3rd stage 5th order (DITRKM5) methods. In Section 2.5, the analyses of the stability polynomial for the DITRK method are presented. In Section 2.6, mentions the DITRK approach with five IVPs. In Section 2.7, the validation of the current approach compared with those in the other literatures of the implicit RK techniques. 2. The Methodology of DITRK Techniques For solving IVPs in eq. (2.1), the prevalent formula of the implicit RK approach for the ๐‘š stage can be expressed as follows: ๐‘ฆ๐‘›+1 = ๐‘ฆ๐‘› + โ„Ž ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘‘๐‘– ๐‘š ๐‘–=1 ๐‘˜๐‘– (2.2) ๐‘ฆ๐‘›+1 โ€ฒ = ๐‘ฆ๐‘› โ€ฒ + โ„Ž ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž2 โˆ‘ ๐‘๐‘– ๐‘š ๐‘–=1 ๐‘˜๐‘– (2.3) ๐‘ฆ๐‘›+1 โ€ฒโ€ฒ = ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž โˆ‘ ๐‘”๐‘– ๐‘š ๐‘–=1 ๐‘˜๐‘– (2.4) and ๐‘˜1 = ๐‘“(๐‘ฅ๐‘›, ๐‘ฆ๐‘›) (2.5) ๐‘˜๐‘– = ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘ฆ๐‘› + โ„Ž ๐‘๐‘– ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘๐‘– 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘Ž๐‘–๐‘— ๐‘–โˆ’1 ๐‘—=1 ๐‘˜๐‘— ) (2.6) where ๐‘– = 2,3, โ€ฆ , ๐‘š . Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 94 The parameters of diagonal implicit RK type (DITRK) methods are presumed as ๐‘๐‘– , ๐‘Ž๐‘–๐‘— , ๐‘‘๐‘– , ๐‘๐‘– , ๐‘”๐‘– where ๐‘–, ๐‘— = 1, 2, 3 โ€ฆ , ๐‘  are real numbers and ๐‘š is referred to stage digit for the approach. This scheme is known as diagonal implicit when ๐‘Ž๐‘–๐‘— โ‰  0 for ๐‘— > ๐‘–. The last denomination includes the single DITRK techniques that ๐ด indicate that the lower the triangular diagonal matric of ๐ด have same values with ๐‘Ž๐‘–๐‘— โ‰  0 where ๐‘– = ๐‘— at the diagonal. The DITRK approach proposed from the work of Butcher, as illustrated in Table 2.1 [20]. Table 2.1: Butcher form DITRK method. 3. Order Conditions of the DITRK Technique According to Mechee et al. [17], the orders of algebraic criteria for RKD approached over order 6 are as follow: Order conditions of ๐‘ฆ: order 3 โˆ‘ ๐‘‘๐‘– = 1 6 (2.7) order 4 โˆ‘ ๐‘‘๐‘– ๐‘๐‘– = 1 24 (2.8) order 5 โˆ‘ ๐‘‘๐‘– ๐‘๐‘– 2 = 1 60 (2.9) order 6 โˆ‘ ๐‘‘๐‘– ๐‘๐‘– 3 = 1 120 and โˆ‘ ๐‘‘๐‘– ๐‘Ž๐‘–,๐‘— = 1/720. (2.10) Order conditions of ๐’šโ€ฒ: order 2 โˆ‘ ๐‘๐‘– = 1 2 (2.11) order 3 โˆ‘ ๐‘๐‘– ๐‘๐‘– = 1 6 (2.12) order 4 โˆ‘ ๐‘๐‘– ๐‘๐‘– 2 = 1 12 (2.13) order 5 โˆ‘ ๐‘๐‘– ๐‘๐‘– 3 = 1 20 and โˆ‘ ๐‘๐‘– ๐‘Ž๐‘–,๐‘— = 1 120 (2.14) order 6 โˆ‘ ๐‘๐‘– ๐‘๐‘– 4 = 1 30 , โˆ‘ ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— = 1 720 and โˆ‘ ๐‘๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— = 1 180 . (2.15) Order conditions of ๐’šโ€ฒโ€ฒ: order 1 โˆ‘ ๐‘”๐‘– = 1 (2.16) Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 95 order 2 โˆ‘ ๐‘”๐‘– ๐‘๐‘– = 1 2 (2.17) order 3 โˆ‘ ๐‘”๐‘– ๐‘๐‘– 2 = 1 3 (2.18) order 4 โˆ‘ ๐‘”๐‘– ๐‘๐‘– 3 = 1 4 and โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— = 1 24 (2.19) order 5 โˆ‘ ๐‘”๐‘– ๐‘๐‘– 4 = 1 5 , โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— = 1 120 and โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— = 1 30 (2.20) order 6 โˆ‘ ๐‘”๐‘– ๐‘๐‘– 2๐‘Ž๐‘–,๐‘— = 1 36 , โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 + โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— = 7 720 , โˆ‘ ๐‘”๐‘– ๐‘๐‘– 5 = 1 6 , โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 = 1 360 , โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— = 1 144 and 1 2 โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 + โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— = 1 120 (2.21) 4. Formation of the 3rd stage 5th order (DITRKM5) Method We implement a diagonal implicit type Rungeโ€“Kutta approach using order conditions derivations as demonstrated in section 2.3, which is developed according to Mechee work [17]. For the ๐‘ order DITRK approach, the local truncation error is defined as follows: for order five: ๐ฟ๐‘‡๐ธorder 5 = [(โˆ‘ ๐‘‘๐‘– ๐‘๐‘– 3 โˆ’ 1 120 )2 + (โˆ‘ ๐‘‘๐‘– ๐‘Ž๐‘–,๐‘— โˆ’ 1 720 )2 + (โˆ‘ ๐‘๐‘– ๐‘๐‘– 4 โˆ’ 1 30 )2 + (โˆ‘ ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— โˆ’ 1 720 )2 + (โˆ‘ ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘– โˆ’ 1 180 )2 + (โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘– 2 โˆ’ 1 36 )2 + (โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— โˆ’ 1 144 )2 + (โˆ‘ ๐‘”๐‘– ๐‘๐‘– 5 โˆ’ 1 6 )2 + (โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 โˆ’ 1 360 )2 + (โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 + โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— โˆ’ 1 720 )2 + ( 1 2 โˆ‘ ๐‘”๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— 2 + โˆ‘ ๐‘”๐‘– ๐‘๐‘– ๐‘Ž๐‘–,๐‘— ๐‘๐‘— โˆ’ 1 120 )2] 1 2 (2.22) the error of local truncation terms for ๐‘ฆ, ๐‘ฆโ€ฒand ๐‘ฆโ€ฒโ€ฒ. The fifth-order three-stage of the DITRKM method in the present study can be computed by employing algebraic order conditions over 5. The System of the result includes 16 nonlinear equations with 16 unknown variables, assuming ๐‘Ž1,1 = ๐‘Ž2,2 and ๐‘Ž2,2 = ๐‘Ž3,3 (2.23) Thus, the calculations of the system products the set of solutions in terms of the parameters ๐‘Ž1,1 , ๐‘Ž2,2 and ๐‘1 as follows: ๐‘Ž2,1 = 0, ๐‘Ž3,1 = 3 20 โˆ’ 3 10 RootOf(10z2 โˆ’ 10z + 1), ๐‘Ž3,2 = 0, ๐‘Ž3,3 = 1 120 RootOf(10z2 โˆ’ 10z + 1), ๐‘1 = โˆ’5 18 RootOf(10z2 โˆ’ 10z + 1) + 5 18 , ๐‘2 = 2 9 , ๐‘3 = 5 18 RootOf(10z2 โˆ’ 10z + 1), ๐‘1 = RootOf(10z2 โˆ’ 10z + 1) , ๐‘2 = 1 2 , ๐‘3 = โˆ’RootOf(10z 2 โˆ’ 10z + 1) + 1, d1 = 1 8 โˆ’ 5 36 RootOf(10z2 โˆ’ 10z + 1), d2 = 1 18 , d3 = 5 36 RootOf(10z2 โˆ’ 10z + 1) โˆ’ 1 72 , ๐‘”1 = 5 18 , ๐‘”2 = 4 9 , ๐‘”3 = 5 18 (2.24) Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 96 Finally, coefficients of the DITRKM method for 5-order 3 stages indicated by DITRKM5 can be read as shown in Table 2.2. Table 2.2: third-stage fifth-order DITRK Method (DITRKM5). 5. The Stability Polynomial of DITRK Method In order to study the stability polynomial of the DITRK method, the following equation is suggested : ๐‘ฆโ€ฒโ€ฒโ€ฒ = โˆ’๐›พ 3๐‘ฆ (2.25) By substituting the DITRK method from eqs. (2.2) - (2.4) to exam eq. (2.25) with stage ๐‘š = 3 are yield ๐‘ฆ๐‘›+1 = ๐‘ฆ๐‘› + โ„Ž ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘‘๐‘– 3 ๐‘–=2 ๐‘˜๐‘– (2.26) ๐‘ฆ๐‘›+1 โ€ฒ = ๐‘ฆ๐‘› โ€ฒ + โ„Ž ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž2 โˆ‘ ๐‘๐‘– 3 ๐‘–=2 ๐‘˜๐‘– (2.27) ๐‘ฆ๐‘›+1 โ€ฒโ€ฒ = ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž โˆ‘ ๐‘”๐‘– 3 ๐‘–=2 ๐‘˜๐‘– (2.28) and ๐‘˜1 = ๐‘“(๐‘ฅ๐‘›, ๐‘ฆ๐‘› ) ๐‘˜๐‘– = ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘ฆ๐‘› + โ„Ž ๐‘๐‘– ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘๐‘– 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘Ž๐‘–๐‘— ๐‘–โˆ’1 ๐‘—=1 ๐‘˜๐‘— ) (2.29) where ๐‘– = 2,3, โ€ฆ , ๐‘š and ๐‘Œ๐‘– = ๐‘ฆ๐‘› + โ„Ž ๐‘๐‘– ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘๐‘– 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘Ž๐‘–๐‘— ๐‘–โˆ’1 ๐‘—=1 (โˆ’๐›พ 3๐‘Œ๐‘— ) (2.30) where ๐‘Œ1 = ๐‘ฆ๐‘› (2.31) ๐‘Œ๐‘– = ๐‘ฆ๐‘› + โ„Ž ๐‘๐‘– ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘๐‘– 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘Ž๐‘–๐‘— ๐‘–โˆ’1 ๐‘—=1 ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘Œ๐‘– ) (2.32) more simplification ๐‘ฆ๐‘›+1 = ๐‘ฆ๐‘› + โ„Ž ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘‘๐‘– ๐‘š ๐‘–=2 (โˆ’๐›พ 3)๐‘Œ๐‘— (2.33) ๐‘ฆ๐‘›+1 โ€ฒ = ๐‘ฆ๐‘› โ€ฒ + โ„Ž ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž2 โˆ‘ ๐‘๐‘– ๐‘š ๐‘–=2 (โˆ’๐›พ 3)๐‘Œ๐‘— (2.34) ๐‘ฆ๐‘›+1 โ€ฒโ€ฒ = ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž โˆ‘ ๐‘”๐‘– ๐‘š ๐‘–=2 (โˆ’๐›พ 3)๐‘Œ๐‘— (2.35) From eq. (2.25), the above equations can be written as follow ๐‘ฆ๐‘›+1 = ๐‘ฆ๐‘› + โ„Ž ๐‘ฆ๐‘› โ€ฒ + โ„Ž2 2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘‘๐‘– ๐‘š ๐‘–=2 ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘Œ๐‘– ) (2.36) Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 97 ๐‘ฆ๐‘›+1 โ€ฒ = ๐‘ฆ๐‘› โ€ฒ + โ„Ž ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž2 โˆ‘ ๐‘๐‘– ๐‘š ๐‘–=2 ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘Œ๐‘– ) (2.37) ๐‘ฆ๐‘›+1 โ€ฒโ€ฒ = ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž โˆ‘ ๐‘”๐‘– ๐‘š ๐‘–=2 ๐‘“(๐‘ฅ๐‘› + ๐‘๐‘– โ„Ž, ๐‘Œ๐‘– ) (2.38) From eq. (2.30), multiply eq. (2.34) by โ„Ž and eq. (2.35) by โ„Ž2,yield โ„Ž๐‘ฆ๐‘›+1 โ€ฒ = โ„Ž๐‘ฆ๐‘› โ€ฒ + โ„Ž2 ๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘๐‘– ๐‘š ๐‘–=2 (โˆ’๐›พ 3)๐‘Œ๐‘— (2.39) โ„Ž2๐‘ฆ๐‘›+1 โ€ฒโ€ฒ = โ„Ž2๐‘ฆ๐‘› โ€ฒโ€ฒ + โ„Ž3 โˆ‘ ๐‘”๐‘– ๐‘š ๐‘–=2 (โˆ’๐›พ 3)๐‘Œ๐‘— (2.40) Then [ ๐‘ฆ๐‘›+1 โ„Ž๐‘ฆ๐‘›+1 โ€ฒ โ„Ž2๐‘ฆ๐‘›+1 โ€ฒโ€ฒ ] = [ 1 1 1 2 0 1 1 0 0 1 ] [ ๐‘ฆ๐‘› โ„Ž๐‘ฆ๐‘› โ€ฒ โ„Ž2๐‘ฆ๐‘› โ€ฒโ€ฒ ] + (โˆ’๐›พ 3โ„Ž3) [ ๐‘‘1 ๐‘‘2 ๐‘‘3 ๐‘1 ๐‘2 ๐‘3 ๐‘”1 ๐‘”2 ๐‘”3 ] [ ๐‘ฆ๐‘› โ„Ž๐‘ฆ๐‘› โ€ฒ โ„Ž2๐‘ฆ๐‘› โ€ฒโ€ฒ ] (2.41) Also, the matrix format of eq. (2.30) can be defined as [ ๐‘Œ1 ๐‘Œ2 โ‹ฎ ๐‘Œ๐‘š ] = [ 1 1 โ‹ฎ 1 0 ๐‘2 โ‹ฎ ๐‘๐‘š 0 ๐‘2 2 โ‹ฎ ๐‘๐‘š 2 ] [ ๐‘ฆ๐‘› โ„Ž๐‘ฆ๐‘› โ€ฒ โ‹ฎ โ„Ž2๐‘ฆ๐‘› โ€ฒโ€ฒ ] + (โˆ’๐›พ3โ„Ž3) [ 0 0 โ‹ฏ 0 ๐‘Ž21 0 โ‹ฏ 0 โ‹ฎ ๐‘Ž๐‘š1 โ‹ฎ ๐‘Ž๐‘š2 โ‹ฑ โ‹ฎ โ€ฆ ๐‘Ž๐‘šโˆ’1 ] [ ๐‘Œ1 ๐‘Œ2 โ‹ฎ ๐‘Œ๐‘š ] (2.42) where ๐‘š = 3. Therefore, [ ๐‘ฆ๐‘›+1 โ„Ž๐‘ฆ๐‘›+1 โ€ฒ โ„Ž2๐‘ฆ๐‘›+1 โ€ฒโ€ฒ ] = ๐‘“(๐ป) [ ๐‘ฆ๐‘› โ„Ž๐‘ฆ๐‘› โ€ฒ โ„Ž2๐‘ฆ๐‘› โ€ฒโ€ฒ ] , ๐ป = (โˆ’๐›พ 3โ„Ž3) (2.43) and ๐‘“(๐ป) = [ 1 + ๐ป๐‘‘๐‘‡ ๐‘ƒโˆ’1๐ธ1 1 + ๐ป๐‘‘ ๐‘‡ ๐‘ƒโˆ’1๐ธ2 1 + ๐ป๐‘‘ ๐‘‡ ๐‘ƒโˆ’1๐ธ3 ๐ป๐‘๐‘‡ ๐‘ƒโˆ’1๐ธ1 1 + ๐ป๐‘ ๐‘‡ ๐‘ƒโˆ’1๐ธ2 1 + ๐ป๐‘ ๐‘‡ ๐‘ƒโˆ’1๐ธ3 ๐ป๐‘”๐‘‡ ๐‘ƒโˆ’1๐ธ1 ๐ป๐‘” ๐‘‡ ๐‘ƒโˆ’1๐ธ2 1 + ๐ป๐‘ ๐‘‡ ๐‘ƒโˆ’1๐ธ3 ] (2.44) where ๐ธ1 = [ 1 1 1 ] , ๐ธ2 = [ 0 ๐‘2 ๐‘3 ] , ๐ธ3 = [ 0 ๐‘2 2 ๐‘๐‘š 2 ] and ๐‘ƒโˆ’1 = (1 โˆ’ ๐ป๐ด)โˆ’1 (2.45) ๐ด = [ 0 0 โ‹ฏ 0 ๐‘Ž21 0 โ‹ฏ 0 โ‹ฎ ๐‘Ž๐‘š1 โ‹ฎ ๐‘Ž๐‘š2 โ‹ฑ โ‹ฎ โ€ฆ ๐‘Ž๐‘šโˆ’1 ] , ๐ต = [ ๐‘‘1 ๐‘‘2 ๐‘‘3 ๐‘1 ๐‘2 ๐‘3 ๐‘”1 ๐‘”2 ๐‘”3 ] (2.46) Thus, the stability polynomial of the DITRK method can be written as โˆ…(๐œ‘, ๐ป) = |๐œ‘๐ผ โˆ’ ๐‘“(๐ป)| (2.47) Where ๐‘“(๐ป) is given value, the characteristic equation is defined as follow, โˆ…(๐œ‘, ๐ป) = ๐‘ƒ0(๐ป)๐œ‘ 3 + ๐‘ƒ1(๐ป)๐œ‘ 2 + ๐‘ƒ2(๐ป)๐œ‘ + ๐‘ƒ3(๐ป) (2.48) 6. Test of Problems The approaches that demonstrated in section 2.3 tested with 5 various problems in this part. The numerical results of the suggested approaches compared with those of other RK techniques at equivalent order which are already available. The numerical experiments were conducted using the following methods: (1) DITRKM5: 3rd stage 5th order DITRK approach computed in the present work. (2) Radau I: 3rd stage 5th order RK technique presented in [20]. Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 98 (3) Radau IA: 3rd stage 5th order RK method studied in [21]. (4) Radau II: 3rd stage 5th order RK scheme tested in [20]. (5) Radau IIA: 3rd stage 5th order RK approach noted in [21]. Problem (1): Consider a nonhomogeneous linear ODE given in [23] ๐‘ฆโ€ฒโ€ฒโ€ฒ(๐‘ฅ) = ๐‘ฆ(๐‘ฅ) + cos(๐‘ฅ), with ๐‘ฆ(0) = 0, ๐‘ฆโ€ฒ(0) = 0, ๐‘ฆโ€ฒโ€ฒ(0) = 1 where ๐‘ฅ โˆˆ [0,1], and analytic solution ๐‘ฆ(๐‘ฅ) = (e๐‘ฅ โˆ’cos(๐‘ฅ)โˆ’sin (๐‘ฅ)) 2 . Problem (2): Consider the nonhomogeneous nonlinear ODE ๐‘ฆโ€ฒโ€ฒโ€ฒ(๐‘ฅ) = (๐‘ฆ(๐‘ฅ))2 + cos2(๐‘ฅ) โˆ’ cos(๐‘ฅ) โˆ’ 1, with ๐‘ฆ(0) = 0, ๐‘ฆโ€ฒ(0) = 1, ๐‘ฆโ€ฒโ€ฒ(0) = 1 where 0 โ‰ค ๐‘ฅ โ‰ค 2, the exact solution ๐‘ฆ(๐‘ฅ) = sin (๐‘ฅ). Problem (3): The nonhomogeneous nonlinear ODEs is considered as ๐‘ฆ1 โ€ฒโ€ฒโ€ฒ(๐‘ฅ) = ๐‘ฆ2(๐‘ฅ), with ๐‘ฆ1(0) = 1, ๐‘ฆ1 โ€ฒ (0) = 0, ๐‘ฆ1 โ€ฒโ€ฒ(0) = 1, ๐‘ฆ2 โ€ฒโ€ฒโ€ฒ(๐‘ฅ) = โˆ’๐‘ฆ1(๐‘ฅ) โˆ’ 2 ๐‘ฆ2(๐‘ฅ) + 2 ๐‘ฆ3(๐‘ฅ) with ๐‘ฆ2(0) = 0, ๐‘ฆ2 โ€ฒ (0) = 1, ๐‘ฆ2 โ€ฒโ€ฒ(0) = 0, ๐‘ฆ3 โ€ฒโ€ฒโ€ฒ(๐‘ฅ) = ๐‘ฆ1(๐‘ฅ) + ๐‘ฆ2(๐‘ฅ) with ๐‘ฆ3(0) = 1, ๐‘ฆ3 โ€ฒ (0) = 1, ๐‘ฆ3 โ€ฒโ€ฒ(0) = 1,With analytic solution ๐‘ฆ1(๐‘ฅ) = cosh (๐‘ฅ) , ๐‘ฆ2(๐‘ฅ) = sinh (๐‘ฅ) and ๐‘ฆ3(๐‘ฅ) = e ๐‘ฅ where 0 โ‰ค ๐‘ฅ โ‰ค 1. 7. Numerical Results Figure (2.1) shows the efficiency of the DITRKM methods created by charting of decimal logarithm for the highest "global error" versus logarithm of function estimate. problem 1 problem 2 problem 3 Figure 2.1: Accuracy curve for DITRKM5, Radau I, Radau IA, Radau II and Radau IIA with h = 0.1, 0.05 0.025, 0.00125, 0.00625 for the problem 1, problem 2 and problem 3. When compared the current study with another implicit RK approach for equivalent order, the DITRKM5 method requires fewer "function evaluations". The digit of equations increased three times with the problems turned to a system of 1st order ODEs. In the comparison, the existing implicit the RK approach with the equivalent order, the "global error" and digit of "function estimate" contain the smallest maximum for the DITRKM5 method at each iteration, as shown in Figure (2.1) that obtained from Table (2.1). As shown in Figure (2.1), the fifth- order three stage results DITRK method (DITRKM5) produces more accurate findings than the other results in the literature (Radau I, Radau IA, Radau II, and Radau IIA). In this work, the logarithm of "maximum global error" is known as a logarithm function for "function 1.8 2 2.2 2.4 2.6 2.8 3 3.2 -7 -6 -5 -4 -3 -2 -1 Log (Number of function call) L o g ( M a x G lo b a l E rr o rs ) DITRKM5 Radau I Radau IA Radau II Radau IIA 2 2.5 3 3.5 -6 -5.5 -5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 Log (Number of function call) L o g ( M a x G lo b a l E rr o rs ) DITRKM5 Radau I Radau IA Radau II Radau IIA 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 -7 -6 -5 -4 -3 -2 -1 0 Log (Number of function call) L o g ( M a x G lo b a l E rr o rs ) DITRKM5 Radau I Radau IA Radau II Radau IIA Ibn Al-Haitham Jour. for Pure & Appl. Sci. 53 (1)2022 99 evaluation" with different step size โ„Ž = 0.1, 0.05, 0.025, 0.0125,0.00625 for five test problems. Table 2.1: Comparisons of number of function call and maximum global error for DITRKM5, Radau I, Radau IA, Radau II and Radau IIA Methods with โ„Ž = 0.1, 0.05 0.025, 0.00125, 0.00625 for the problem 1, problem 2 and problem 3. Problem 3 Problem 2 Problem 1 Method Step size (h) Maximum Global Error Maximum Global Error Maximum Global Error No. of Function Call Maximum Global Error No. of Function Call 9.74073E-05 88 0.000277124 160 9.16352E-05 88 DITRKM5 0.1 0.05488292 99 0.02489423 180 0.02986368 99 Radau I 0.06335586 99 0.02867864 180 0.03449261 99 Radau IA 0.05488292 99 0.02647426 180 0.02878467 99 Radau II 0.06335586 99 0.0298746 180 0.03336877 99 Radau IIA 1.8304E-05 160 6.8347E-05 320 1.74282E-05 160 DITRKM5 0.05 0.02293305 180 0.01292113 360 0.01273117 180 Radau I 0.02656216 180 0.01494992 360 0.01475188 180 Radau IA 0.02293305 180 0.01360768 360 0.01229666 180 Radau II 0.02656216 180 0.015539 360 0.0143079 180 Radau IIA 4.67234E-06 320 1.79521E-05 648 4.45635E-06 320 DITRKM5 0.025 0.0115538 360 0.006847777 729 0.006421128 360 Radau I 0.01340439 360 0.007940234 729 0.007451075 360 Radau IA 0.0115538 360 0.007152807 729 0.006195875 360 Radau II 0.01340439 360 0.008219884 729 0.007223443 360 Radau IIA 1.22981E-06 648 4.35276E-06 1288 1.1728E-06 648 DITRKM5 0.0125 0.005945227 729 0.003387183 1449 0.003298104 729 Radau I 0.006903284 729 0.003931975 1449 0.003829934 729 Radau IA 0.005945227 729 0.003535766 1449 0.003179202 729 Radau II 0.006903284 729 0.004074293 1449 0.003710422 729 Radau IIA 3.02667E-07 1288 2.88938E-06 2560 2.88938E-07 1288 DITRKM5 0.00625 0.002941504 1449 0.001667861 2880 0.00163419 1449 Radau I 0.003416977 1449 0.001937206 2880 0.001898433 1449 Radau IA 0.002941504 1449 0.001741931 2880 0.001575303 1449 Radau II 0.003416977 1449 0.001741931 2880 0.001839395 1449 Radau IIA 8. 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