Research Journal of Mathematics and Statistics 5(4): 32-42, 2013 ISSN: 2042-2024, e-ISSN: 2040-7505 © Maxwell Scientific Organization, 2013 Submitted: August 31, 2013 Accepted: September 10, 2013 Published: November 30, 2013 A Modified Block Adam Moulton (MOBAM) Method for the Solution of Stiff Initial Value Problems of Ordinary Differential Equations G.M. Kumleng, J.P. Chollom and S. Longwap Department of Mathematics, University of Jos, P.M.B. 2084, Plateau State, Nigeria Abstract: Stiff ordinary differential equations pose computational difficulties as they present severe step size restrictions on the numerical methods to be used. Construction of numerical methods that possess suitable stability properties for the solution of such systems has been the target of many researchers. Development of methods suitable for these systems of equations has been either through the use of derivative of the solution or by introducing off-step points, additional stages or super future points. These processes have been exploited in Runge-Kutta methods or linear multistep methods. In this study, an improved class of linear multistep block method has been constructed based on Adams Moulton block methods. The improved methods are shown to be A-stable, a property desirable to handle stiff ODEs. Methods of uniform orders 10 and 11 have been constructed. The efficiency of the new methods tested on stiff systems of ODEs and the results reveal that the MOBAM methods compare favourably with results obtained using the state of the art Matlab Ode23 solver. Keywords: Block method, initial value problems, non-linear, stability INTRODUCTION In this study, we pursue the path of Adams Moulton methods by constructing A-stable block linear multistep methods of uniform order 10 and 11. These methods are obtained by modifying the Adams Moulton method of step number 9 by reducing its interpolation step number from 8 to 3. This approach is similar to that of Brugnano and Trigiante (1998) where they developed the Generalized Adams methods. The modified methods are constructed using the concept of multistep collocation of Lie and Norsett (1989) which Onumanyi et al. (1994, 1999) referred to as block linear multistep methods. The block methods are arrived at by evaluating the continuous formulation of the new method at grid and off grid points to yield the discrete schemes used as block integrators. The methods are applied simultaneously producing selfstarting methods thus eliminating the issue of overlap of pieces of solutions. Stiff initial value problems of ordinary differential equations were realized in 1952 arising from the study of chemical kinetics. Since then, many researches have been involved in the study and development of suitable numerical methods to handle them. Curtiss and Hirschfelder (1952), Mitchell and Craggs (1953) and Gear (1971) developed the Backward Differential Formulae which were used to solve stiff problems arising from chemical kinetics. Intensive work done in this regard yielding several efficient numerical algorithms has appeared in the literature. Because of the severe restriction on step size placed on Adams Moulton methods for the solution of stiff ODEs, Garfinket et al. (1978) introduced the concept of Astability for linear multistep methods. This property became the minimum requirement for any linear multistep method to be used for the solution of stiff ODEs. Achieving A-stability was difficult, other stability requirements such as A(α)-stability and stiffly stability were considered. Chakrararti and Kamel (1983) developed stiffly stable second derivative methods with high order and improved stability regions to handle stiff problems. Several other researchers such as Samir (2013), Evelyn and Renante (2006), Song (2010), Vlachos et al. (2009) and Ali and Gholamreza (2012) developed improved and more friendly numerical methods with improved stability properties that could handle stiff ODEs with various degrees of stiffness. CONSTRUCTION OF THE NEW METHOD The k-step general linear multistep method for numerically solving the differential equation: y ' =f ( x, y ), y ( x0 ) =y0 , x ∈ [a, b], y ∈ R (1) is described by the linear difference equation: k ∑α j =0 k j ( x) yn+ j =h∑ β j ( x) f n+ j j =0 Corresponding Author: G.M. Kumleng, Department of Mathematics, University of Jos, P.M.B. 2084, Plateau State, Nigeria 32 (2) Res. J. Math. Stat., 5(4): 32-42, 2013 With h being the step size, α j (x) and β j (x) being the continuous coefficients of the method. The new improved nine step method based on the Adams Moulton method is defined as: m yn + v − α v −1 ( x) yn + v −1 = h∑ β j ( x) f n + j (3) j =0 where, v = k2−1 , α v −1 and β j ( x) are the continuous coefficients of the method, m is the number of distinct collocation points, h is the step size and k = m − 1 = 3,5,7,9,... Using the method in Onumanyi et al. (1994, 1999) and further studied by Kumleng et al. (2012) and Chollom et al. (2012) the method (3) for v = k2−1 and j =0, 1… 9 sequence in the matrix form: DC = I (4) where, D = C −1 , C −1 being the elements of the continuous coefficients of the method. Construction of MOBAM K = 9: This method has its general form as: k (5) y ( x) = α 3 ( x) yn+3 + h∑ β j ( x) f n+ j , j = 0,1,...,9 j =0 Using the procedure in Onumanyi et al. (1999), we obtain the D matrix for (5) as: 1 xn + 3 0 1 0 1 0 1 0 1 D = 0 1 0 1 0 1 0 1 0 1 0 1 xn2+ 3 2 xn 2 xn +1 2 xn + 2 2 xn + 3 2 xn + 4 2 xn + 5 2 xn + 6 xn3+ 3 3xn2 3xn2+1 3xn2+ 2 3xn2+ 3 3xn2+ 4 3xn2+ 5 3xn2+ 6 xn4+ 3 4 xn3 4 xn3+1 4 xn3+ 2 4 xn3+ 3 4 xn3+ 4 4 xn3+ 5 4 xn3+ 6 xn5+ 3 5 xn4 5 xn4+1 xn6+ 3 6 xn5 6 xn5+1 xn7+ 3 xn8+ 3 7 xn6 8 xn7 6 7 xn +1 8 xn7+1 5 xn4+ 2 5 xn4+ 3 5 xn4+ 4 5 xn4+ 5 5 xn4+ 6 6 xn5+ 2 6 xn5+ 3 6 xn5+ 4 6 xn5+ 5 6 xn5+ 6 7 xn6+ 2 7 xn6+ 3 7 xn6+ 4 7 xn6+ 5 7 xn6+ 6 xn9+ 3 x10 n+3 8 9 xn 10 xn9 9 xn8+1 10 xn9+1 9 xn8+ 2 10 xn9+ 2 9 xn8+ 3 10 xn9+ 3 9 xn8+ 4 10 xn9+ 4 9 xn8+ 5 10 xn9+ 5 9 xn8+ 6 10 xn9+ 6 9 xn8+ 7 10 xn9+ 7 8 9 9 xn +8 10 xn +8 9 xn8+ 9 10 xn9+ 9 8 xn7+ 2 8 xn7+ 3 8 xn7+ 4 8 xn7+ 5 8 xn7+ 6 2 xn + 7 3xn2+ 7 4 xn3+ 7 5 xn4+ 7 6 xn5+ 7 7 xn6+ 7 8 xn7+ 7 2 xn +8 3xn2+8 4 xn3+8 5 xn4+8 6 xn5+8 7 xn6+8 8 xn7+8 2 xn + 9 3xn2+ 9 4 xn3+ 9 5 xn4+ 9 6 xn5+ 9 7 xn6+ 9 8 xn7+ 9 (6) Using the Maple software, the inverse of the matrix (6) is obtained and represented as C, the elements of which yield the continuous coefficients α 3 (x) and β j (x), j = 0,1,…9 of the method (5) as: α 3 ( x) = 1 µ µ µ 6515µ 4523µ 19µ 3013µ 5µ 29µ 3591h β 0 ( x) = ( − 12800 + µ − 7129 5040h + 6048h − 9072h + 128h − 103680h + 1344h − 96768h + 72576h − 3628800h ) 2 β1 ( x ) = ( − 147429h 89600 9µ 2 2h + 4609µ 3 840h 2 − 3 4 5 2 3 4 14139µ 4 4480h 3 + 7667µ 5 7200h 4 − 6 7807µ 6 34560h 5 + 7 5 − 8 6 11µ 7 360h 6 + 9 7 59µ 8 23040h 7 − 10 8 11µ 9 90720h8 + 9 µ 10 403200h 9 ) µ µ µ µ µ 563µ 7µ 43µ 279h ) β 2 ( x) = ( 1600 − 9 µh + 5869 − 20837 + 24901 − 6787 + 5040 − 720 + 90720 − 100800 h h h h 420h 2240h 7200h 8640h 2 3 4 2 h β 3 ( x) = ( − 13273 5600 + β 4 ( x) = ( 19107h 8960 − 14µ 2 h 63µ 2 4h − 3 6289µ 3 270h 2 6499µ 3 240h 2 + 5 + − 6 4 72569µ 4 4320h 3 6519µ 4 320h 3 + − 7 5 4013µ 5 600h 4 122249µ 5 14400h 4 8 6 + 13873µ 6 8640h 5 − 36769µ 6 17280h 5 9 7 − 401µ 7 1680h 6 + 3313µ 7 10080h 6 + 8 31µ 8 1440h 7 − 10 − 353µ 8 11520h 7 9 7µ9 6480h8 + + 41µ 9 25920h8 µ 10 43200h 9 − ) (7) µ 10 28800h 9 ) µ µ 63µ 265µ 1091µ 5273µ 32773µ 305µ 67µ h β 5 ( x) = ( − 73809 44800 + 5 h − 12h + 64h − 720h + 17280h − 1008h + 2304h − 648h + 28800h ) 2 3 4 2 5 3 6 4 7 5 8 6 9 10 7 8 9 µ 7µ 6709µ 84307µ 10279µ 9823µ 313µ 53µ 13µ h β 6 ( x) = ( 5039 5600 − h + 540h − 8640h + 2400h − 8640h + 1680h − 2880h + 12960h − 43200h ) 2 3 4 2 3663h β 7 ( x) = ( − 11200 + 18µ 2 7h − 5 3 967µ 3 210h 2 + 6 4 4101µ 4 1120h 3 − 2939µ 5 1800h 4 + 7 8 5 6 3817µ 6 8640h 5 373µ 7 5040h 6 − 9 7 + 10 8 151µ 8 20160h 7 − 9 19µ 9 45360h8 + µ 10 100800h9 ) µ µ µ 3407µ 3487µ 347µ 41µ 37 µ 909h ) β 8 ( x) = ( 12800 − 916µh + 33360 − 1823 + 10579 − 34560 + 20160 − 23040 + 362880 − 403200 2240h 28800h h h h h h h 2 3 4 2 3 5 6 4 5 7 8 6 9 7 10 8 9 µ µ 761µ 29531µ 89µ 1069µ 13µ 25h ) β 9 ( x) = (− 3584 + 18µ h − 7560 + 362880 − 2400 + 103680 − 560µ h + 69120 − 90720 + 3628800 h h h h h h h 2 3 4 2 3 5 6 4 7 5 8 6 33 9 7 10 8 9 Res. J. Math. Stat., 5(4): 32-42, 2013 Substituting the continuous coefficients (7) into (5) yields the continuous form of the MOBAM method (8): 6515 µ 4523 µ 19 µ 3013 µ 5µ 29 µ µ µ µ 3591h y ( xn + µ ) = y n+3 + (− 12800 + µ − 7129 5040 h + 6048 h 2 − 9072 h 3 + 128 h 4 − 103680 h 5 + 1344 h 6 − 96768 h 7 + 72576 h8 − 3628800 h 9 ) f n + 2 3 4 5 6 7 8 9 10 9µ 4609 µ 14139 µ 7667 µ 7807 µ 11µ 59 µ 11µ µ h (− 147429 89600 + 2 h − 840 h 2 + 4480 h 3 − 7200 h 4 + 34560 h 5 − 360 h 6 + 23040 h 7 − 90720 h8 + 403200 h 9 ) f n +1 + 2 3 4 5 6 7 8 9 10 563 µ 7µ 43 µ µ µ µ µ µ 279 h − 9 µh + 5869 − 20837 + 24901 − 6787 + 5040 − 720 + 90720 − 100800 ( 1600 ) f n+2 + h6 h7 h8 h9 420 h 2 2240 h 3 7200 h 4 8640 h 5 2 3 4 5 6 7 8 9 10 14 µ 6289 µ 72569 µ 4013 µ 13873 µ 401µ 31µ 7µ µ h (− 13273 5600 + h − 270 h 2 + 4320 h 3 − 600 h 4 + 8640 h5 − 1680 h 6 + 1440 h 7 − 6480 h8 + 43200 h 9 ) f n +3 + 2 3 4 5 6 7 8 9 10 63 µ 6499 µ 6519 µ 122249 µ 36769 µ 3313 µ 353 µ 41µ µ h ( 19107 8960 − 4 h + 240 h 2 − 320 h3 + 14400 h 4 − 17280 h5 + 10080 h 6 − 11520 h 7 + 25920 h8 − 28800 h9 ) f n + 4 + 2 3 4 5 6 7 8 9 10 (8) 63 µ 265 µ 1091µ 5273 µ 32773 µ 305 µ 67 µ µ µ h (− 73809 44800 + 5 h − 12 h 2 + 64 h3 − 720 h 4 + 17280 h5 − 1008 h 6 + 2304 h 7 − 648 h8 + 28800 h9 ) f n + 5 + 2 3 4 5 6 7 8 9 10 7µ 6709 µ 84307 µ 10279 µ 9823 µ 313 µ 53 µ 13 µ µ h ( 5039 5600 − h + 540 h 2 − 8640 h3 + 2400 h 4 − 8640 h5 + 1680 h 6 − 2880 h 7 + 12960 h8 − 43200 h9 ) f n + 6 + 2 3 4 5 6 7 8 9 10 373 µ 151µ 19 µ µ µ µ µ µ 3663 h + 187µh − 967 + 4101 − 2939 + 3817 − 5040 + 20160 − 45360 + 100800 (− 11200 ) f n+7 + h6 h7 h8 h9 210 h 2 1120 h3 1800 h 4 8640 h5 2 3 4 5 6 7 8 9 10 3407 µ 3487 µ 347 µ 41µ 37 µ µ µ µ 909 h − 916µh + 33360 − 1823 + 10579 − 34560 + 20160 − 23040 + 362880 − 403200 ( 12800 ) f n +8 + h2 h5 h6 h7 h8 h9 2240 h3 28800 h 4 2 3 4 5 6 7 8 9 10 761µ 29531µ 89 µ 1069 µ 13 µ µ µ 25 h + 18µ h − 7560 + 362880 − 2400 + 103680 − 560µ h6 + 69120 − 90720 + 3628800 (− 3584 ) f n +9 h2 h3 h4 h5 h7 h8 h9 2 3 4 5 6 7 8 9 10 where, µ = x − x n and µ ∈ [0, 9h ] . Evaluating the continuous scheme (8) at the following points µ = 0, h, 2h, 4h, 5h, 6h, 7 h, 8h, 9h yields the MOBAM method (9) for k = 9 used in block for the solution of ODEs: y n +3 − y n = h 89600 (25137 f n + 147429 f n+1 − 15624 f n+ 2 + 212368 f n+3 − 191070 f n+ 4 + 147618 f n+5 − 80624 f n+6 + 29304 f n+7 − 6363 f n+8 + 625 f n+9 ) h yn+1 − yn+3 = 113400 (729 f n − 38938 f n+1 − 156340 f n+ 2 − 18742 f n+3 − 28234 f n+ 4 + 24266 f n+5 − 13492 f n+6 + 4910 f n+7 − 1063 f n+8 + 104 f n+9 ) y n + 2 − y n +3 = h 7257600 y n + 4 − y n +3 = h 7257600 (−10625 f n + 163531 f n+1 − 3133688 f n+ 2 − 5597072 f n+3 + 2166334 f n+ 4 − 1295810 f n+5 + 617584 f n+6 − 206072 f n+7 + 42187 f n+8 − 3969 f n+9 ) (−3969 f n + 50315 f n+1 − 342136 f n+ 2 + 3609968 f n+3 + 4763582 f n+ 4 − 1166146 f n+5 + 462320 f n+6 − 141304 f n+7 + 27467 f n+8 − 2497 f n+9 ) h yn+5 − yn+3 = 113400 (−23 f n + 334 f n+1 − 2804 f n+ 2 + 46378 f n+3 + 139030 f n+ 4 + 46378 f n+5 − 2804 f n+6 + 334 f n+7 − 23 f n+8 ) y n+ 6 − y n+3 = h 89600 (−49 f n + 603 f n+1 − 3960 f n+ 2 + 42352 f n+3 + 95454 f n+ 4 + 95454 f n+5 + 42352 f n+6 − 3960 f n+7 + 603 f n+8 − 49 f n+9 ) h yn+7 − yn+3 = 14175 (13 f n+1 − 224 f n+ 2 + 5494 f n+3 + 17632 f n+ 4 + 10870 f n+5 + 17632 f n+6 + 5494 f n+7 − 224 f n+8 + 13 f n+9 ) y n +8 − y n + 3 = h 290304 y n+9 − y n+3 = h 1400 (−425 f n + 4675 f n+1 − 25400 f n+ 2 + 171760 f n+3 + 247150 f n+ 4 + 381550 f n+5 + 185200 f n+6 + 387400 f n+7 + 101635 f n+8 − 2025 f n+9 ) (9) (9 f n − 90 f n+1 + 396 f n+ 2 − 598 f n+3 + 3798 f n+ 4 − 1494 f n+5 + 3980 f n+6 − 306 f n+7 + 2313 f n+8 + 392 f n+9 ) Construction of Hybrid MOBAM K = 9, µ = 172 : This is the hybrid form of the MOBAM family for k=9. An off step point is inserted in (5) to give its general form as: k y ( x) = α 3 ( x) yn+3 + h∑ β j ( x) f n+ j + hβ u ( x) f n+u , j = 0,1,...,9, µ = 172 j =0 Following a similar procedure as in above section gives the matrix: 34 (10) Res. J. Math. Stat., 5(4): 32-42, 2013 1 xn+3 0 1 0 1 0 1 0 1 0 1 D= 0 1 0 1 0 1 0 1 0 1 0 1 xn2+3 2 xn 2 xn+1 2 xn+ 2 2 x n +3 2 xn+ 4 2 xn +5 2 xn+6 2 xn + 7 2 x n +8 2 xn+ 17 2 xn3+3 3xn2 3xn2+1 3xn2+ 2 3xn2+3 3xn2+ 4 3xn2+5 3xn2+6 3xn2+7 3 xn2+8 3 xn2+ 17 2 xn4+3 4 xn3 4 xn3+1 4 xn3+ 2 4 xn3+3 4 xn3+ 4 4 xn3+5 4 xn3+6 4 xn3+7 4 xn3+8 4 xn3+ 17 2 xn5+3 5 xn4 5 xn4+1 5 xn4+ 2 5 xn4+3 5 xn4+ 4 5 xn4+5 5 xn4+6 5 xn4+7 5 xn4+8 5 xn4+ 17 2 xn6+3 6 xn5 6 xn5+1 6 xn5+ 2 6 xn5+3 6 xn5+ 4 6 xn5+5 6 xn5+6 6 xn5+7 6 xn5+8 6 xn5+ 17 2 xn7+3 7 xn6 7 xn6+1 7 xn6+ 2 7 xn6+3 7 xn6+ 4 7 xn6+5 7 xn6+6 7 xn6+7 7 xn6+8 7 xn6+ 17 2 xn8+3 8 xn7 8 xn7+1 8 xn7+ 2 8 xn7+3 8 xn7+ 4 8 xn7+5 8 xn7+6 8 xn7+7 8 xn7+8 8 xn7+ 17 2 xn9+3 9 xn8 9 xn8+1 9 xn8+ 2 9 xn8+3 9 xn8+ 4 9 xn8+5 9 xn8+6 9 xn8+7 9 xn8+8 9 xn8+ 17 2 x10 n +3 10 xn9 10 xn9+1 10 xn9+ 2 10 xn9+3 10 xn9+ 4 10 xn9+5 10 xn9+6 10 xn9+7 10 xn9+8 10 xn9+ 17 2 xn +9 3 xn2+9 4 xn3+9 5 xn4+9 6 xn5+9 7 xn6+9 8 xn7+9 9 xn8+9 10 xn9+9 2 x11 n +3 10 11xn 11x10 n +1 11x10 n+ 2 10 11xn+3 11x10 n+ 4 11x10 n +5 10 11xn+6 11x10 n+7 11x10 n +8 10 11xn+ 17 2 11x10 n +9 (11) The continuous coefficients of the method (10) are similarly obtain from the inverse of (11) as: α 3 ( x) = 1 β 0 ( x) = − 4581629h 126233µ 2 610807µ 3 366199µ 4 1205177µ 5 76871µ 6 +µ− + − + − + 16755200 85680h 514080h 2 616896h 3 6168960h 4 1762560h 5 3419µ 7 1123µ 8 167µ 9 107µ 10 µ 11 − + − + 514080h 6 1645056h 7 3701376h 8 61689600h 9 33929280h 10 β 1 ( x) = − 1693113h 51µ 2 83393µ 3 7921µ 4 9335µ 5 12937µ 6 + − + − + 985600 10h 12600h 2 1920h 3 6048h 4 34560h 5 − 677µ 7 149µ 8 µ9 µ 10 µ 11 + − + − 3326400 11200h 6 23040h 7 2268h 8 57600h 9 407367h 153µ 2 104813µ 3 401181h 4 3713351µ 5 165181µ 6 − + − + − + 13h 112320h 5 5460h 2 29120h 3 655200h 4 8008000 β 2 ( x) = 8179µ 7 1039µ 8 2299µ 9 103µ 10 µ 11 − + − + 32760h 6 37440h 7 1179360h 8 1310400h 9 720720h 10 β 3 ( x) = − 759127µ 5 332153µ 6 h 238µ 2 111953µ 3 1384609h 4 4461461 + − + − + 11h 1355200 2970h 2 47520h 3 59400h 4 95040h 5 − 8581µ 7 2257µ 8 367µ 9 101µ 10 µ 11 + − + − 13860h 6 31680h 7 71280h 8 475200h 9 261360h 10 376763h 119µ − 4h 98560 β 4 ( x) = 2 + 115523µ 3 123821h 4 2547601µ 5 96619µ 6 − + − + 2160h 2 2880h 3 129600h 4 17280h 5 3103µ 7 1403µ 8 703µ 9 11µ 10 µ 11 − + − + 3024h 6 11520h 7 77760h 8 28800h 9 142560h 10 β 5 ( x) = − 1882809h 153µ 2 23533µ 3 20667h 4 109279µ 5 109723µ 6 + − + − + − 492800 5h 420h 2 448h 3 5040h 4 17280h 5 (12) 1727µ 7 337µ 8 101µ 9 97µ 10 µ 11 + − + − 1440h 6 2304h 7 9072h 8 201600h 9 110880h 10 360737h 119µ 2 119093µ 3 318847µ 4 381983µ 5 45733µ 6 − + − + − + 5h 2700h 2 8640h 3 21600h 4 8640h 5 123200 β 6 ( x) = 12893µ 7 23µ 8 43µ 9 19µ 10 µ 11 − + − + 12600h 6 180h 7 4320h 8 43200h 9 118800h 10 β 7 ( x) = − 15627h 102µ 2 17159µ 3 77453µ 4 423559µ 5 29467µ 6 + − + − + − 8800 7h 630h 2 3360h 3 37800h 4 8640h 5 1693µ 7 863µ 8 103µ 9 31µ 10 µ 11 + − + − 2520h 6 10080h 7 15120h 8 100800h 9 166320h10 1140903h 153µ 2 60439µ 3 2457µ 4 1521413µ 5 80437µ 6 − + − + − + 16h 3360h 2 160h 3 201600h 4 3456oh 5 985600 β 8 ( x) = 4693µ 7 1391µ 8 1777µ 9 13µ 10 µ 11 −− + − + 6 7 8 9 10080h 23040h 362880h 57600h 221760h10 35 Res. J. Math. Stat., 5(4): 32-42, 2013 β ( x ) = − 17 2 3046144h 65536µ 2 116801536µ 3 1334272µ 4 148209664µ 5 + − + − + 4679675 12155 11486475h 2 153153h 3 34459425h 4 9728µ 6 3085312µ 7 256µ 8 59392µ 9 512µ 10 1024µ 11 − + − + − 7293h 5 11486475h 6 7293h 7 20675655h 8 3828825h 9 379053675h10 22423h 17 µ 2 4499µ 3 556819µ 4 345019µ 5 24581µ 6 − + − + − + 18h 2520h 2 362880h 3 453600h 4 103680h 5 197120 β 9 ( x ) = 83µ 7 437 µ 8 71µ 9 89 µ 10 µ 11 − + − + 1728h 6 69120h 7 136080h 8 3628800h 9 1995840h10 f n +9 Substituting the continuous coefficients (12) into (10) produces the continuous form of the new MOBAM method for k = 9, µ = 172 as: 4581629h 126233µ 2 610807 µ 3 366199 µ 4 1205177 µ 5 76871µ 6 − +µ − + − + − + y(µ + x n ) = y n+3 + 85680h 514080h 2 616896h 3 6168960h 4 1762560h 5 16755200 7 8 9 10 11 µ 3419 µ 1123µ 167 µ 107 µ fn + − + − + 514080h 6 1645056h 7 3701376h 8 61689600h 9 33929280h 10 1693113h 51µ 2 83393µ 3 7921µ 4 9335µ 5 12937 µ 6 − 985600 + 10h − 12600h 2 + 1920h 3 − 6048h 4 + 34560h 5 − µ9 µ 10 µ 11 677 µ 7 149 µ 8 f n +1 + + − + − 3326400 11200h 6 23040h 7 2268h 8 57600h 9 407367 h 153µ 2 104813µ 3 401181h 4 3713351µ 5 165181µ 6 8008000 − 13h + 5460h 2 − 29120h 3 + 655200h 4 − 112320h 5 + µ 11 8179 µ 7 1039 µ 8 2299 µ 9 103µ 10 − + − + 32760h 6 37440h 7 1179360h 8 1310400h 9 720720h 10 f n+2 + 4461461h 238µ 2 111953µ 3 1384609h 4 759127 µ 5 332153µ 6 − 1355200 + 11h − 2970h 2 + 47520h 3 − 59400h 4 + 95040h 5 µ 11 8581µ 7 2257 µ 8 367 µ 9 101µ 10 f n+3 + − + − + − 13860h 6 31680h 7 71280h 8 475200h 9 261360h 10 119 µ 376763h − 4h 98560 2 + 115523µ 3 123821h 4 2547601µ 5 96619 µ 6 − + − + 2160h 2 2880h 3 129600h 4 17280h 5 µ 11 3103µ 7 1403µ 8 703µ 9 11µ 10 f n+4 + − + − + 3024h 6 11520h 7 77760h 8 28800h 9 142560h 10 153µ 2 23533µ 3 20667 h 4 109279 µ 5 109723µ 6 1882809h + − + − + − − 492800 5h 420h 2 448h 3 5040h 4 17280h 5 µ 11 1727 µ 7 337 µ 8 101µ 9 97 µ 10 f n +5 + + − + − 1440h 6 2304h 7 9072h 8 201600h 9 110880h 10 360737 h 119 µ 2 119093µ 3 318847 µ 4 381983µ 5 45733µ 6 + − + − + 123200 − 5h 2700h 2 8640h 3 21600h 4 8640h 5 µ 11 12893µ 7 23µ 8 43µ 9 19 µ 10 f n+6 + − + − + 12600h 6 180h 7 4320h 8 43200h 9 118800h 10 15627 h 102 µ 2 17159µ 3 77453µ 4 423559µ 5 29467 µ 6 − − + − + − + 8800 7h 630h 2 3360h3 37800h 4 8640h5 µ 11 1693µ 7 863µ 8 103µ 9 31µ 10 fn+7 + + − + − 2520h 6 10080h 7 15120h8 100800h9 166320h10 1140903h 153µ 2 60439 µ 3 2457 µ 4 1521413µ 5 80437 µ 6 + − + − + − + 16h 3360h 2 160h3 201600h 4 3456oh5 985600 µ 11 4693µ 7 1391µ 8 1777 µ 9 13µ 10 f n +8 + −− + − + 10080h 6 23040h 7 362880h8 57600h9 221760h10 3046144h 65536 µ 2 116801536 µ 3 1334272 µ 4 148209664 µ 5 + − + + − + − 12155 11486475h 2 153153h3 34459425h 4 4679675 6 7 8 9 10 11 9728µ 3085312 µ 256 µ 59392 µ 512 µ 1024 µ f 17 + − + − + − 7293h5 11486475h 6 7293h 7 20675655h8 3828825h9 379053675h10 n + 2 36 (13) Res. J. Math. Stat., 5(4): 32-42, 2013 22423 h 17 µ 2 4499 µ 3 556819 µ 4 345019 µ 5 24581 µ 6 83 µ 7 − + − + − + − 2 3 4 5 18 h 2520 h 362880 h 453600 h 103680 h 1728 h 6 197120 437 µ 8 71 µ 9 89 µ 10 µ 11 f + − + 7 8 9 10 n + 9 69120 h 136080 h 3628800 h 1995840 h µ = x − x n and µ ∈ [0, 9h] . where, µ = 0, h, 2h, 4h, 5h, 6h, 7 h, 8h, Evaluating the continuous scheme (13) at the following points h, 9h yields the discrete members of the Modified Block Hybrid Adams Method (MOBHAM) used as block integrators as: 17 2 h y n -y n+3 = - 2395993600 ( 655172947 f n+4115957703 f n+1- 1218842064 f n+2+7887863048 f n+3-9159108530 f n+4+9154217358 f n+5 7015613176 f n+6+4254794544 f n+7 -2773535193 f n+8+1559625728 f n+17 -272551565 f n+9 ) 2 h y n+1-y n+3 = 9097288200 ( 50461697 f n -3041910300 f n+1- 12919661700 f n+2 -462284706 f n+3-4173983242 f n+4+4401077538 f n+5 3373129188 f n+6+2030152410 f n+7 -1312470159 f n+8+735182848 f n+17 -128011598 f n+9 ) 2 h y n+2 -y n+3= - 5822264448 00 ( 607643465 f n -10622743131 f n+1+ 239872909584 f n+2+480783779736 f n+3-232034579062 f n+4+178839894090 f n+5 119438161128 f n+6+66455799696 f n+7 -40827431931 f n+8+22431268864 f n+17 -3841935383 f n+9 ) 2 h y n+4 -y n+3= - 5822264448 00 ( 188536777 f n - 2711763483 f n+1+ 21333375888 f n+2 -272743194984 f n+3-413057496566 f n+4+133291433418 f n+5 74179086696 f n+6+37828966032 f n+7 -22073336571 f n+8+11903565824 f n+17 -2007444439 f n+9 ) 2 h y n+5 -y n+3= - 9097288200 ( 1469039 f n -22958364 f n+1+ 207240132 f n+2 -3671758974 f n+3-11242913110 f n+4 -3605498754 f n+5+ 117533988 f n+6+49927878 f n+7 -55696641 f n+8+34471936 f n+17 -6393530 f n+9 ) 2 h y n+6 -y n+3 = - 2395993600 ( 676819 f n -9663225 f n+1+ 76071600 f n+2 -1050296312 f n+3-2703306034 f n+4 -2358687474 f n+5 1313459576 f n+6+235126320 f n+7 -113048793 f n+8+58064896 f n+17 -9459021 f n+9 ) 2 h y n+7 -yn+3 = - 1137161025 ( 177320 f n - 2851563 f n+1+ 26317632 f n+2 - 463764522 f n+3-1372289776 f n+4 -926283930 f n+5 1363849344 f n+6 -476918442 f n+7+45099912 f n+8 -16252928 f n+17 +1971541 f n+9 ) 2 5h y n+8 -yn+3 =- 2328905779 2 ( 1480765 f n - 20558967 f n+1+ 156227280 f n+2 -2062826376 f n+3-5235912110 f n+4 -4488330990 f n+5 4496046984 f n+6 -5126687280 f n+7 -2447435991 f n+8+489291776 f n+17 -58258915 f n+9 ) 2 11h y n+17 -yn+3 = - 2463635865 600 (60848359 f n - 868413975 f n+1 + 2 6868940100 f n+2 - 97078557732 f n+3 - 256542831974 f n+4 - 207787036314 f n+5 227009590236 f n+6 - 232587334980 f n+7 - 189017501673 f n+8 - 27073183744 f n+17 - 783270631 f n+9 ) 2 h y n+9 -yn+3= - 37437400 ( 15301 f n -204204 f n+1+ (14) 1460844 f n+2 -17238442 f n+3-40641458 f n+4 -38375766 f n+5 33324148 f n+6 -44035134 f n+7 -22688523 f n+8 -23461888 f n+17 -6130982 f n+9 ) 2 STABILITY ANALYSIS OF THE NEW BLOCK METHODS The block method (9) is represented by a matrix finite difference equation in block form as: A (1) Yw+1 = A (0) Yw + hB (1) Fw (15) 37 Res. J. Math. Stat., 5(4): 32-42, 2013 where, Yw+1 = ( y n +1 , y n + 2 , y n + 3 , y n + 4 , y n + 5 , y n + 6 , y n + 7 , y n +8 , y n + 9 ) T Yw = ( y n −8 , y n − 7 , y n − 6 , y n −5 , y n − 4 , y n −3 , y n − 2 , y n −1 , y n ) T Fw = ( f n +1 , f n + 2 , f n + 3 , f n + 4 , f n + 5 , f n + 6 , f n + 7 , f n +8 , f n + 9 ) T for w = 0, … and n = 0, 9, …, N-9 and the matrices A (1) , A (0) , B (1) being 9 by 9 matrices whose entries are given by the coefficients of (9) and are as defined in equation (16) below: 1 0 0 0 0 0 0 0 0 0 − 1 0 0 0 0 0 0 0 1 − 1 0 0 0 0 0 0 0 − 1 1 0 0 0 0 0 0 (1) 0 − 1 0 1 0 0 0 0, A = 0 0 − 1 0 0 1 0 0 0 0 0 0 − 1 0 0 0 1 0 0 0 − 1 0 0 0 0 1 0 0 0 0 − 1 0 0 0 0 0 1 A( 0 ) 0 1 0 0 = 0 0 0 0 0 B (1) 147429 89600 − 19469 56700 163531 7257600 10063 1451520 167 = 56700 603 89600 13 14175 4675 290304 −9 140 0 − 279 1600 − 7817 5670 − 391711 907200 − 42767 907200 − 701 28350 − 99 2240 − 32 2025 − 3175 36288 99 350 13273 5600 − 9371 56700 − 349817 453600 225623 453600 23189 56700 2647 5600 5494 14175 10735 18144 − 299 700 − 19107 8960 − 14117 56700 1083167 3628800 2381791 3628800 13903 11340 47727 44800 17632 14175 123575 145152 1899 700 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 73809 44800 12133 56700 − 129581 725760 − 583073 3628800 23189 56700 47727 44800 2174 2835 190775 145152 − 747 700 − 5039 5600 − 3373 28350 38599 453600 5779 90720 − 701 28350 2647 5600 17632 14175 11575 18144 199 70 3663 11200 491 11340 − 25759 907200 − 17663 907200 167 56700 − 99 2240 5494 14175 48425 36288 − 153 700 − 909 12800 − 1063 113400 42187 7257600 27467 7257600 − 23 113400 603 89600 − 32 2025 101635 290304 2313 1400 25 3584 13 14175 −7 12800 − 2497 7257600 0 −7 12800 13 14175 − 25 3584 7 25 (16) where, w = 0,1,2,...9 and n is the grid index. Zero-stability: Zero-stability is concerned with the stability of the difference system (15) as h tends to zero. Thus, as h → 0 , the method (15) tends to the difference system: A (1) Yw+1 = A (0) Yw (17) whose first characteristic polynomial ρ (λ ) is given by: ρ (λ ) = λA (0) − A(1) (18) Substituting A( 0) , A(1) from (16) into the characteristics polynomial ρ (λ ) (18) gives: ρ (λ ) = λA (0) − A(1) = λ8 (λ − 1) (19) By Fatunla (1991), the block method (9) is zero-stable since in (19), ρ (λ ) = 0 satisfies λ j ≤ 1, j = 1,... and for those roots with λ j = 1 , the multiplicity does not exceed 1. The block method is therefore convergent according to 38 Res. J. Math. Stat., 5(4): 32-42, 2013 2.5 mobam mobham 2 1.5 1 Im(z) 0.5 0 -0.5 -1 -1.5 -2 -2.5 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Re(z) Fig. 1: Absolute stability regions of the MOBAM methods 4 y1 mobam y2 mobam y1 ode23 y2 ode23 3 Solution(y) 2 1 0 -1 -2 -3 1 0 2 3 4 5 Time(t) 6 7 8 9 10 Fig. 2: Solution of example 1 using (10) and ode23 24307 28249 36919 c12 = ( 5420800 , 54885600 ,− 188179200 , Henrici (1962). Since the MOBAM method is both consistent and zero-stable, it is convergent. Using the same procedure, the MOBHAM method in (14) is also zero-stable and consistent, hence convergent. 37987 4997 443 ,− 164656800 ,− 5420800 , − 439084800 31 5905 4908607 17 T ,− 52690176 ,− 5945425920 ,− 96800 ) − 1715175 0 Order of the MOBAM methods: The orders and error constants of the new block methods are obtained using Chollom et al. (2007). The block method (10) is of uniform order (10,10,10,10,10,10,10,10,10)T with error constants: Absolute stability region of the MOBAM methods: Following Chollom et al. (2007) and Butcher (1985), the block methods (9) and (14) are reformulated as General linear methods and the region of absolute stability of the method was plotted using the matlab program and is shown in Fig. 1. Figure 1 reveals that the MOBAM methods are Astable. NUMERICAL EXPERIMENTS 11899 5609 c11 = (− 1971200 ,− 7484400 , 171137 479001600 443 1971200 90817 263 , 479001600 , 7484400 , 18665 179 T 62 ,− 467775 , 19160064 ,− 30800 ) In this section, the MOBAM methods (9) and (14) are tested on linear and nonlinear stiff initial value problems of ODEs. The solution curves obtained for the MOBAM methods are compared with the well-known MATLAB ODE 23 solver. while the block method (15) is of uniform order with error (11,11,11,11,11,11,11,11,11,11)T constants: 39 Res. J. Math. Stat., 5(4): 32-42, 2013 4 y1 mobham y2 mobham y1 ode23 y2 ode23 3 Solution(y) 2 1 0 -1 -2 -3 0 1 2 3 4 5 Time(t) 7 6 8 9 10 Fig. 3: Solution of example 1 using (15) and ode23 1 y1 mobam y2 mobam y1 ode23 y2 ode23 0.9 0.8 0.7 Solution(y) 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 Time(t) 7 6 8 9 10 Fig. 4: Solution of example 2 using (10) and ode23 1 y1 mobham y2 mobham y1 ode23 y2 ode23 0.9 0.8 0.7 Solution(y) 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1 2 3 4 5 Time(t) Fig. 5: Solution of example 2 using (15) and ode23 40 6 7 8 9 10 Res. J. Math. Stat., 5(4): 32-42, 2013 3 y1 mobam y2 mobam y1 ode23 y2 ode23 2.5 2 Solution(y) 1.5 1 0.5 0 -0.5 -1 -1.5 0 1 2 3 4 5 Time(t) 6 7 8 9 10 Fig. 6: Solution of example 3 using (10) and ode23 3 y1 mobham y2 mobham y1 ode 23 y2 ode 23 2.5 2 Solution(y) 1.5 1 0.5 0 -0.5 -1 -1.5 0 1 2 3 4 5 Time(t) 6 7 8 9 10 Fig. 7: Solution of example 3 using (15) and ode23 y1' = −(ε −1 + 2) y1 + ε −1 y 22 , y1 (0) = 1 Example 1: We consider a well -known classical system experimented in Baker (1989), Stabrowski (1997), Vigo-Aguiar and Ramos (2007) and Akinfenwa et al. (2011), in the range 0 ≤ t ≤ 10 : y = 998 y1 + 1998 y 2 , ' 1 y = −999 y1 − 1999 y 2 , ' 2 y 2' = y1 − y 2 − y 22 , y1 (0) = 1 The smaller is the ε , the more serious the stiffness of the system. Its exact solution is given by (Fig. 4 and 5): y1 (0) = 1 y1 (0) = 1 y1 = y 22 , y 2 = e − t , h = 0.1, ε = 10 Its exact solution is given by the sum of two decaying exponential components: −t y1 = 4e − 3e −1000 t −t , y1 = −2e + 3e −8 Example 3: Consider the stiff problem; see Brugnano and Trigiante (1998): −1000 t y1' = −2 y1 + y 2 + 2 sin x, y1 (0) = 2 The stiffness ratio is 1:1000, h = 0.1 (Fig. 2 and 3) y 2' = 998 y1 − 999 y 2 + 999(cos x − sin x), y1 (0) = 3 Example 2: Consider the stiffly nonlinear problem which was proposed by Kaps et al. (1981) in the range 0 ≤ t ≤ 10. The stiffness ratio of the problem is 1000. h = 0.1, 0≤x≤10. Its exact solution is given by (Fig. 6 and 7): 41 Res. J. Math. Stat., 5(4): 32-42, 2013 y1 ( x) = 2e − x + sin x, y 2 ( x) = 2e − x + cos x Garfinket, D., C.D. Morbachi and N.Z. Shapiro, 1978. Stiff differential equations. Ann. Rev. Biophys. Bioeng., 6: 525-542. Gear, C.W., 1971. Numerical Initial Value Problems in Ordinary Differential Equations. Prentice-Hall, Englewood Cliffs, NJ. Henrici, P., 1962. Discrete Variable Methods in Ordinary Differential Equations. John Wiley, New York, pp: 407. Kaps, P., G. Dahlguist and R. Jeltsch, 1981. Rosenbrock-type Methods. In: Berich, G.D. and R. Jeltsch (Eds.), Vol. 9, Numerical Methods for Stiff Initial Value Problems. For Geometric and Practical Mathematic, the RWTH Aachen, Germany. Kumleng, G.M., U.W. Sirisena and J.P. Chollom, 2012. Construction of a class of block hybrid implicit multistep methods for the solution of stiff ordinary differential equations. Niger. J. Pure Appl. Sci., 5. Lie, I. and S.P. Norsett, 1989. Super convergence for multistep collocation. Math. Comput., 52(185): 65-79. Mitchell, A.R. and J.W. Craggs, 1953. Stability of difference relations in the solution of ordinary differential equations. Math. Comput., 7: 127-129. Onumanyi, P., D.O. Awoyemi, S.N. Jator and U.W. Sirisena, 1994. New linear multistep methods with continuous coefficients for first order initial value problems. J. Niger. Math. Soc., 13: 37-51. Onumanyi, P., U.W. Sirisena and S.N. Jator, 1999. Continuous finite difference approximations for solving differential equations. Int. J. Comput. Math., 72: 15-27. Samir, K., 2013. Improved accuracy of linear multistep methods. App. Math. Inf. Sci., 7(2): 491-496. Song, M.H., 2010. The improved linear multistep methods for DE with piecewise continuous arguments. Appl. Math. Comput., 217(8): 4002-4009. Stabrowski, M.M., 1997. An efficient algorithm for solving stiff ordinary differential equations. Simul. Pract. Th., 5(4): 333-344. Vigo-Aguiar, J. and H. Ramos, 2007. A family of astable runge-kutta collocation methods for higher order for initial value problems. IMA J. Numer. Anal., 27(4): 798. Vlachos, D.S., Z.A. Anastassi and T.E. Simos, 2009. A new family of multistep methods with improved phase-lag characteristics for the integration of orbital problems. Astronom. J., 138(86). CONCLUSION New MOBAM methods have been proposed and implemented as self-starting methods for the solution of stiff ordinary differential equations. The MOBAM methods are A-stable making them suitable for the numerical solution of stiff problems. The accuracy and efficiency of the new block methods have been demonstrated on both linear and non-linear stiff problems as can be seen in Fig. 2 to 7. The authors in the next work will address the theoretical aspect and implementation strategies of the MOBAM class. REFERENCES Akinfenwa, O., S. Jato and N. Yoa 2011. An eight order backward differentiation formula with continuous coefficients for stiff ordinary differential equations. Int. J. Math. Comput. Sci., 7: 4. Ali, K.E. and H. Gholamreza, 2012. Third derivative multistep methods for stiff systems. Int. J. Nonlin. Sci., 14(4): 443-450. 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Improved linear multistep methods for small noise ODE’s. PAMM. Proc. Appl. Math. Mech., 6: 661-662. Fatunla, S.O., 1991. Block method for second order differential equations. Int. J. Comput. Math., 41: 55-63. 42