Volume 3, Issue 6 e1204
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Pricing passport option using higher order compact scheme

Ankur Kanaujiya

Ankur Kanaujiya

Department of Mathematics, Indian Institute of Technology Guwahati, Guwahati, India

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Siddhartha P. Chakrabarty

Corresponding Author

Siddhartha P. Chakrabarty

Department of Mathematics, Indian Institute of Technology Guwahati, Guwahati, India

Correspondence Siddhartha P. Chakrabarty, Department of Mathematics, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India.

Email: [email protected]

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First published: 10 October 2021
Funding information: There are no funders to report for this submission.

Abstract

Higher order compact scheme (HOC) is used for pricing both European and American type passport option. We consider the problem for two different cases, namely, the symmetric case (which has a closed form solution) and the non-symmetric case. For the symmetric case HOC schemes result in slightly improved results as compared to the classical Crank–Nicolson implicit method, while still giving approximately second order convergence rate. In order to improve the convergence rate, grid stretching near zero accumulated wealth is introduced in the HOC schemes. The consequent higher order compact scheme with grid stretching gives better results with the rate of convergence being close to third order. For non-symmetric case we also observe similar results for both European and American type passport option. In absence of any analytic formula for the non-symmetric case, convergence rate was calculated using double-mesh differences.

1 INTRODUCTION

Passport options having a trading account as the underlying was designed at the Bankers Trust in 19971 with the purpose of hedging against losses incurred by the trading account. The passport option is effectively a call option on the balance of a trading account,2 wherein the holder retains the gains from the trading account during the life of the option. In particular, Hyer et al.1 consider trading on an asset, with the price and number of units held at time t, being denoted by S ( t ) and u ( t ) , respectively, with u ( t ) [ 1 , 1 ] . Consequently, at expiration T, the holder will receive an amount of max w ( T ) , 0 from the writer, with w ( t ) denoting accumulated wealth at time t. Accordingly, in a complete market, the price of the passport option is given by
𝒱 ( S , w , t ) = sup | u ( t ) | < 1 𝔼 e r ( T t ) max w ( T ) , 0 | S ( t ) = S , w ( t ) = w ,
where r is the riskfree rate and 𝔼 is the expectation under the risk-neutral measure . Using the pricing partial differential equation (PDE) approach, the valuation PDE for passport option (after using the transformation x = w / S ) is given by References 2, 3,
v t + ( u x ) ( r γ ) v x + 1 2 ( u x ) 2 σ 2 2 v x 2 = γ v , x , t [ 0 , T ] . ()
where v ( x , t ) is the transformed option price and
u = sign ( r γ ) v x x σ 2 2 v x 2 . ()
Here σ is the volatility of the geometric Brownian motion (GBM) driven asset pricing model for S ( t ) and γ is the cost of carry, with u representing the optimal trading strategy chosen by the holder of the option. Taking into account the non-existence of a closed form pricing formula in the nonsymmetric case, where the riskfree rate is not identical to the cost of carry (a closed form solution exists for the symmetric case when both are identical), several numerical approaches to this pricing problem have been adopted. The numerical approaches were designed essentially for obtaining the numerical solution to the PDE. Various theoretical and numerical aspects of passport options, as well as options on trading account can be found in References 2-18. Obtaining precise and accurate solutions to PDEs on a compact stencil can be accomplished through higher order compact (HOC) schemes. Several HOC schemes for problems with both Dirichlet and Neumann boundary conditions have appeared in References 19-23 and have found applications in pricing of options as well.24, 25 Given the specific nature of the pricing PDE for passport options, we are interested in those HOC schemes which do not require the coefficients to be smooth.22, 23, 26, 27 In this article, we construct a set of fourth-order HOC schemes for the pricing of European passport option (on a trading account whose value is contingent on the price of a traded risky security), for which the boundary conditions are both Dirichlet and Neumann in nature. The set of schemes presented are fourth order accurate in space at all the grid points including both the interior and boundary points. The boundary conditions at the boundaries, x min = exp ( 4 σ T ) and x max = exp ( 4 σ T ) along with the final condition are as follows:
v ( x min , t ) = 0 , ()
v x ( x max , t ) = e r ( T t ) , ()
v ( x , T ) = max x , 0 . ()
Equation (1) can be written as
v t + 𝒜 ( x , u ) v x + ( x , u ) 2 v x 2 = γ v , ()
where 𝒜 ( x , u ) = ( u x ) ( r γ ) and ( x , u ) = 1 2 ( u x ) 2 σ 2 .

2 THE HIGHER ORDER COMPACT SCHEMES

We present the compact difference schemes both for the interior as well as the boundary points, following the approach in Reference 22. Accordingly, let Δ t denote the uniform temporal mesh size with the m-th time point being t m = m Δ t , 0 m N , where N is the number of temporal intervals and Δ t = T N . For the spatial uniform mesh, we consider M spatial points x j = x min + ( j 1 ) Δ x , 1 j M , with the mesh size being Δ x = x max x min ( M 1 ) . The approximation of v ( x , t ) , v x ( x , t ) , v x x ( x , t ) , and u ( x , t ) at the point ( x j , t m ) are denoted by v j m , ( v x ) j m , ( v x x ) j m , and ( u ) j m , respectively. We note that the time discretization of Equation (6) using the Crank–Nicolson implicit method (CNIM) is given by,
v j m + 1 v j m Δ t + 𝒜 x j , ( u ) j m + 1 ( v x ) j m + 1 + ( v x ) j m 2 + x j , ( u ) j m + 1 ( v x x ) j m + 1 + ( v x x ) j m 2 = γ v j m + 1 + v j m 2 . ()

We now construct the fourth-order approximation for the term ( v x ) j m and ( v x x ) j m .

2.1 The interior points

We first consider all the interior points ( x j , t m ) , where 3 j M 2 and 0 m N 1 . The following compact schemes26, 27 are used to derive a fourth-order approximation to ( v x ) j m and ( v x x ) j m
a 1 ( v x ) j + 1 m + b 1 ( v x ) j m + c 1 ( v x ) j 1 m = v j + 1 m v j 1 m 2 Δ x , ()
a 2 ( v x x ) j + 1 m + b 2 ( v x x ) j m + c 2 ( v x x ) j 1 m = v j + 1 m 2 v j m + v j 1 m ( Δ x ) 2 . ()
where the coefficients are determined by matching the Taylor series expansion up to fourth order terms in Δ x and are,
a 1 = c 1 = 1 6 , b 1 = 2 3 and a 2 = c 2 = 1 12 , b 2 = 5 6 .
Substituting these values in (8) and (9) we obtain,
1 4 ( v x ) j + 1 m + ( v x ) j m + 1 4 ( v x ) j 1 m = 3 2 v j + 1 m v j 1 m 2 Δ x , 3 j M 2 , 0 m N 1 . ()
1 10 ( v x x ) j + 1 m + ( v x x ) j m + 1 10 ( v x x ) j 1 m = 6 5 v j + 1 m 2 v j m + v j 1 m ( Δ x ) 2 , 3 j M 2 , 0 m N 1 . ()

2.2 The boundary points

We next consider the fourth order approximation to ( v x ) 2 m , ( v x x ) 2 m , ( v x ) M 1 m , and ( v x x ) M 1 m near the actual boundary points x 1 and x M . At the left boundary ( x 1 , t m ) we have the Dirichlet boundary condition, v ( x 1 , t m ) = 0 . The following compact schemes are used to derive a fourth-order approximation to ( v x ) 2 m and ( v x x ) 2 m for 0 m N 1 ,
d 1 ( v x ) 2 m + e 1 ( v x ) 3 m = 1 Δ x f 1 v 1 m + g 1 v 2 m + h 1 v 3 m , ()
( v x x ) 2 m + k ( v x x ) 3 m = 1 ( Δ x ) 2 k 1 v 1 m + k 2 v 2 m + k 3 v 3 m + k 4 v 4 m + k 5 v 5 m + k 6 v 6 m , ()
where the coefficients are determined by matching the Taylor series expansion up to fourth order terms in Δ x and are,
d 1 = 4 , e 1 = 2 , f 1 = 1 , g 1 = 4 , h 1 = 5 and k = 1 2 , k 1 = 19 24 , k 2 = 7 12 , k 3 = 19 12 , k 4 = 11 6 , k 5 = 13 24 , k 6 = 1 12 .
Substituting these values in (12) and (13) we obtain,
4 ( v x ) 2 m + 2 ( v x ) 3 m = 1 Δ x v 1 m 4 v 2 m + 5 v 3 m . ()
( v x x ) 2 m + 1 2 ( v x x ) 3 m = 1 ( Δ x ) 2 19 24 v 1 m 7 12 v 2 m 19 12 v 3 m + 11 6 v 4 m 13 24 v 5 m + 1 12 v 6 m . ()
At the right boundary ( x M , t m ) we have the Neumann boundary condition, v x ( x M , t m ) = e r ( T t m ) . The following compact schemes are used to derive a fourth-order approximation to ( v x ) M 1 m and ( v x x ) M 1 m ,
d 2 ( v x ) M 2 m + e 2 ( v x ) M 1 m + f 2 ( v x ) M m = 1 ( Δ x ) g 2 v M 1 m + h 2 v M 2 m , ()
d 3 ( v x x ) M 2 m + e 3 ( v x x ) M 1 m + 1 Δ x f 3 ( v x ) M m = 1 ( Δ x ) 2 g 3 v M 1 m + h 3 v M 2 m , ()
where the coefficients are determined by matching the Taylor series expansion up to fourth order terms in Δ x and are,
d 2 = 5 , e 2 = 8 , f 2 = 1 , g 2 = 12 , h 2 = 12 and d 3 = 1 / 3 , e 3 = 11 / 6 , f 3 = 1 , g 3 = 1 , h 3 = 1 .
Substituting these values in (16) and (17) we obtain,
5 ( v x ) M 2 m + 8 ( v x ) M 1 m = ( v x ) M m + 1 Δ x 12 v M 1 m 12 v M 2 m . ()
( 4 ) ( v x x ) M 2 m + 22 ( v x x ) M 1 m = 12 Δ x ( v x ) M m + 1 ( Δ x ) 2 12 v M 1 m + 12 v M 2 m . ()

Thus the set of schemes, consisting of (7), (10), (11), (14), (15), (18), and (19) has the overall order of O Δ t 2 + Δ x 4 .

We now introduce a few notations prior to representing the numerical scheme (7) in the matrix form. At the time level t m , 0 m N 1 , we have
v m = v 2 m , , v M 1 m , v x m = ( v x ) 2 m , , ( v x ) M 1 m , v x x m = ( v x x ) 2 m , , ( v x x ) M 1 m
A = 1 1 2 1 10 1 1 10 1 4 22 , B = 7 / 24 19 / 24 11 / 12 13 / 48 1 / 24 6 12 6 6 12 6 6 6 , ()
D = 4 2 1 4 1 1 4 1 5 8 , E = 4 5 3 0 3 3 0 3 12 12 . ()
( C ) m = 19 24 ( Δ x ) 2 v 1 m , 0 , , 0 , 12 Δ x ( v x ) M m , ( F ) m = 1 Δ x v 1 m , 0 , , 0 , ( v x ) M m . ()
Using these notations, the schemes in (11), (15), and (19) can be written as
A ( v x x ) m = 2 ( Δ x ) 2 B ( v ) m + ( C ) m ()
Similarly, the schemes in (10), (14), and (18) can be written as
D ( v x ) m = 1 Δ x E ( v ) m + ( F ) m . ()
The invertibility of matrices A and D shows the solvability of (23) and (24) which can be proved using the Gerschgorin theorem.28 Simplifying (23) and (24) we obtain
( v x x ) m = 2 ( Δ x ) 2 A 1 B ( v ) m + A 1 ( C ) m . ()
( v x ) m = 1 Δ x D 1 E ( v ) m + D 1 ( F ) m . ()
Using (25) and (26) in the CNIM (7) we obtain,
( v ) m + 1 ( v ) m Δ t + 1 2 Δ x S m + 1 D 1 E ( v ) m + 1 + ( v ) m + 1 2 S m + 1 D 1 ( F ) m + 1 + ( F ) m + 1 ( Δ x ) 2 R m + 1 A 1 B ( v ) m + 1 + ( v ) m + 1 2 R m + 1 A 1 ( C ) m + 1 + ( C ) m ) = γ 2 ( v ) m + 1 + ( v ) m ) , ()
where R and S are diagonal matrices given by
S m + 1 = diag ( α 2 m + 1 , α 3 m + 1 , α M 1 m + 1 ) , α j m + 1 = 𝒜 x j , ( u ) j m + 1 , R m + 1 = diag ( β 2 m + 1 , β 3 m + 1 , β M 1 m + 1 ) , β j m + 1 = x j , ( u ) j m + 1 . ()
Upon further simplification, (27) becomes
1 + γ Δ t 2 I 1 2 q S m + 1 D 1 E p R m + 1 A 1 B ( v ) m = 1 γ Δ t 2 I + 1 2 q S m + 1 D 1 E + p R m + 1 A 1 B ( v ) m + 1 + Δ t 2 S m + 1 D 1 ( F ) m + 1 + ( F ) m + Δ t 2 R m + 1 A 1 ( C ) m + 1 + ( C ) m ) , ()
where I is the identity matrix of size ( M 2 ) × ( M 2 ) , p = Δ t ( Δ x ) 2 and q = Δ t Δ x .
The discretization of u in (2) using the HOC schemes is
( u ) j m = sign ( r γ ) 2 ( v x ) j m + 1 + ( v x ) j m 1 2 x j σ 2 ( v x x ) j m + 1 + ( v x x ) j m , ()
which upon further simplification using (25) and (26) results in
( u ) m = sign ( r γ ) 2 Δ x D 1 E ( v ) m + 1 + ( v ) m + ( r γ ) 2 D 1 ( F ) m + 1 + ( F ) m σ 2 1 ( Δ x ) 2 T A 1 B ( v ) m + 1 + ( v ) m σ 2 2 T A 1 ( C ) m + 1 + ( C ) m . ()
where
( u ) m = ( ( u ) 2 m , , ( u ) M 1 m )
and T is the diagonal matrix given by
T = diag ( x 2 , x 3 , , x M 1 ) . ()

We developed a HOC scheme in space and used Crank–Nicolson scheme for the time discretization only. For the purpose of subsequent discussion, HOC scheme would mean HOC scheme in space and Crank–Nicolson scheme in time, as detailed in this section.

3 GRID STRETCHING

While HOC schemes result in better convergence as compared to the CNIM, we observed that such improvement using HOC schemes is somewhat limited near the zero accumulated gain. The payoff (final condition) for the passport option is non-smooth at the zero accumulated wealth. Since the accuracy of a finite difference approximation depends on the existence of several derivatives in the Taylor's series approximation, but at zero accumulated wealth, the payoff is not differentiable, therefore in order to improve the accuracy, we need the local mesh refinement near the zero accumulated wealth. Therefore, in order to improve the convergence rate as well as reduce the maximum error due to non-smooth nature of the final condition, we use a stretching transformation24, 25 to obtain HOC schemes with grid stretching (HOCGS). The transform using the transformed coordinate y [ 0 , 1 ] is given by
x = ϕ ( y ) = 1 ξ sinh ( c 2 y + c 1 ( 1 y ) ) + k , ()
where ξ is the stretching parameter, c 1 = sinh 1 ( ξ ( x min k ) ) , c 2 = sinh 1 ( ξ ( x max k ) ) and k is the stretched coordinate (which for our problem is k = 0 that is, near the zero accumulated wealth). Using the transformed variable V ( y , t ) = v ( x , t ) , the Equations (1)–(5) can be rewritten as,
V t + 𝔸 ( y , u ) V y + 𝔹 ( y , u ) 2 V y 2 = γ V , ()
u ( y , t ) = sign ( y ) V y ( y ) 2 V y 2 , ()
V ( 0 , t ) = 0 , ()
V y ( 1 , t ) = J ( 1 ) e r ( T t ) , ()
V ( y , T ) = max ϕ ( y ) , 0 . ()
with
J ( y ) = ϕ y = c 2 c 1 ξ cosh ( c 2 y + c 1 ( 1 y ) ) , ()
H ( y ) = 2 ϕ y 2 = ( c 2 c 1 ) 2 ξ sinh ( c 2 y + c 1 ( 1 y ) ) , ()
𝔸 ( y , u ) = ( u ϕ ( y ) ) ( r γ ) J ( y ) 1 2 ( u ϕ ( y ) ) 2 σ 2 H ( y ) ( J ( y ) ) 3 , ()
𝔹 ( y , u ) = 1 2 ( u ϕ ( y ) ) 2 σ 2 ( J ( y ) ) 2 , ()
( y ) = ( r γ ) J ( y ) + σ 2 ϕ ( y ) H ( y ) ( J ( y ) ) 3 , ()
( y ) = σ 2 ϕ ( y ) ( J ( y ) ) 2 . ()
In order to discretize (34) and (35) over the transformed domain [ 0 , 1 ] , we use Δ y = 1 M 1 , y j = ( j 1 ) Δ y , 1 j M with Δ t being the same as previously defined. The time discretization of (34) using the CNIM is as follows,
V j m + 1 V j m Δ t + 𝔸 y j , ( u ) j m + 1 ( V y ) j m + 1 + ( V y ) j m 2 + 𝔹 y j , ( u ) j m + 1 ( V y y ) j m + 1 + ( V y y ) j m 2 = γ V j m + 1 + V j m 2 . ()
The fourth order approximation to V y and V y y (similar to that of v x and v x x ) are as follows,
( V y y ) m = 2 ( Δ y ) 2 A 1 B ( V ) m + A 1 ( C g s ) m . ()
( V y ) m = 1 Δ y D 1 E ( V ) m + D 1 ( F g s ) m , ()
where the matrices A, B , D , E are same as given in (20), (21) and
( C g s ) m = 19 24 ( Δ y ) 2 V 1 m , 0 , , 0 , 12 Δ y ( V y ) M m T , ( F g s ) m = 1 Δ y V 1 m , 0 , , 0 , ( V y ) M m T .
Using (46) and (47), Equation (45) can be written as,
( V ) m + 1 ( V ) m Δ t + 1 2 Δ y 𝕊 m + 1 D 1 E ( V ) m + 1 + ( V ) m + 1 2 𝕊 m + 1 D 1 ( F g s ) m + 1 + ( F g s ) m + 1 ( Δ y ) 2 m + 1 A 1 B ( V ) m + 1 + ( V ) m + 1 2 m + 1 A 1 ( C g s ) m + 1 + ( C g s ) m ) = γ 2 ( V ) m + 1 + ( V ) m ) , ()
where and 𝕊 are diagonal matrices given by
𝕊 m + 1 = diag ( α 2 m + 1 , α 3 m + 1 , , α M 1 m + 1 ) , α j m + 1 = 𝔸 y j , ( u ) j m + 1 , m + 1 = diag ( β 2 m + 1 , β 3 m + 1 , , β M 1 m + 1 ) , β j m + 1 = 𝔹 y j , ( u ) j m + 1 . ()
Upon further simplification, (48) becomes
1 + γ Δ t 2 I 1 2 q 1 𝕊 m + 1 D 1 E p 1 m + 1 A 1 B ( V ) m = 1 γ Δ t 2 I + 1 2 q 1 𝕊 m + 1 D 1 E + p 1 m + 1 A 1 B ( V ) m + 1 + Δ t 2 𝕊 m + 1 D 1 ( F g s ) m + 1 + ( F g s ) m + Δ t 2 m + 1 A 1 ( C g s ) m + 1 + ( C g s ) m ) , ()
where I is the identity matrix of size ( M 2 ) × ( M 2 ) , p 1 = Δ t Δ y 2 and q 1 = Δ t Δ y .
The discretization of u ( y , t ) using HOC is as follows
( u ) j m = sign 1 2 ( y j ) ( V y ) j m + 1 + ( V y ) j m 1 2 ( y j ) ( V y y ) j m + 1 + ( V y y ) j m , ()
which upon further simplification, by using (47) and (46) results in
( u ) m = sign 𝒫 D 1 E 2 Δ y 𝒬 A 1 B ( Δ y ) 2 ( V ) m + 1 + ( V ) m + 1 2 𝒫 D 1 ( F g s ) m + 1 + ( F g s ) m 1 2 𝒬 A 1 ( C g s ) m + 1 + ( C g s ) m ) . ()
where
( u ) m = ( ( u ) 2 m , , ( u ) M 1 m ) ,
and 𝒫 and 𝒬 are diagonal matrices given by
𝒫 = diag ( ( y 2 ) , ( y 3 ) , , ( y M 1 ) ) . 𝒬 = diag ( ( y 2 ) , ( y 3 ) , , ( y M 1 ) ) .
The price of an American passport option, v ^ ( x , t ) satisfies (1) and (2) on the continuation region denoted by c , where c = ( x , t ) × [ 0 , T ) : v ^ ( x , t ) > max ( x , 0 ) , subject to the free boundary condition and terminal condition,
v ^ ( x , t ) max ( x , 0 ) , ( x , t ) ()
and
v ^ ( x , T ) = max ( x , 0 ) . ()
In order to determine the value of the American passport option numerically, the following early exercise condition3
v ^ i , j = max ( v i , j , max ( x , 0 ) ) , ()
where v i , j is the solution of (29) and (50) in case of and HOC and HOCGS schemes, respectively, is used.

4 NUMERICAL RESULTS

We now present the numerical results of the HOC and the HOCGS schemes obtained in Sections 2 and 3, respectively. A comparison of results using both the schemes along with the CNIM is presented, to illustrate the advantage of the application of HOC over CNIM with even more improved results that follow from the application of the HOCGS schemes.

We begin with the symmetric case of r = γ where we have the advantage of comparing the results with the analytic solution. The parameters used for the simulations (carried out in MatLabTM) were the same that were used in the CNIM implementation carried out in Reference 3, that is, S ( t ) = 100 , r = 0 , γ = 0 , σ = 30 % , and T t = 1 . The simulations were carried out for several values of M and N. However, the tabulated results presented here are only for M = 800 and N = 800 . The prices for the symmetric case are tabulated in Table 1. We observe that the HOC scheme gives slightly better results as compared to the CNIM scheme. The inclusion of grid stretching through the HOCGS scheme further improves the results by giving values that closely match the analytic values. To further observe these improvements, the loglog plot of the maximum error against the number of spatial steps (M) for all the schemes are given in Figure 1. Note that this comparison was not restricted to only M = 800 , but for several values of M, namely M = 21, 41, 81, 161, and 321. It is clear that there is a marginal reduction in maximum error for the HOC scheme, but significant reduction if HOCGS scheme is used. The maximum error, the rate of convergence, and the CPU time for all the three schemes are tabulated in Table 2. We observe that both CNIM and HOC achieve only second order convergence while the HOCGS achieves close to third order convergence. While the convergence achieved through numerical implementation using HOCGS is unable to achieve fourth order accuracy, one does achieve better accuracy as compared to the CNIM scheme.

Details are in the caption following the image
Loglog plot of maximum error against M for the European passport option with S ( t ) = 100 , r = 0 , γ = 0 , σ = 30 % , T t = 1 , and N = 800 with ξ = 13
TABLE 1. Price of the European passport option with S ( t ) = 100 , r = 0 , γ = 0 , σ = 30 % , T t = 1 , M = 800 , and N = 800 with ξ = 13
w Analytic CNIM HOC HOCGS
20 5.887568 5.886553 5.886658 5.887572
10 8.880836 8.879288 8.879603 8.880844
5 10.830686 10.828835 10.829259 10.830680
2 12.169565 12.168752 12.169237 12.169553
1 12.646019 12.644768 12.645272 12.646016
0 13.138099 13.135937 13.136459 13.138079
1 13.646019 13.644768 13.645272 13.646016
2 14.169565 14.168752 14.169237 14.169553
5 15.830686 15.828835 15.829259 15.830680
10 18.880836 18.879288 18.879603 18.880844
20 25.887568 25.886553 25.886658 25.887572
TABLE 2. Maximum error, rate of convergence and CPU time for the European passport option with S ( t ) = 100 , r = 0 , γ = 0 , σ = 30 % , T t = 1 , and N = 800 with ξ = 13
Spatial nodes 21 41 81 161 321
CNIM error 3.203367 0.873704 0.216691 0.054095 0.013519
CNIM order - 1.874372 2.011507 2.002059 2.000502
CPU time (s) 0.050000 0.050000 0.150000 0.360000 1.370000
HOC error 2.442399 0.651655 0.163756 0.040994 0.010252
HOC order - 1.906119 1.992564 1.998047 1.999559
CPU time (s) 0.080000 0.360000 0.860000 4.020000 171.6900
HOCGS error 0.568289 0.144473 0.028900 0.004692 0.000673
HOCGS order - 1.975826 2.321656 2.622644 2.800841
CPU time (s) 0.100000 0.510000 1.200000 6.770000 51.68000
Prior to implementation of the nonsymmetric case of r γ (for which there is no analytic solution) it is necessary to specify the method of calculation of maximum error and the rate of convergence in this case. Accordingly, the maximum error and rate of convergence is computed using the double-mesh principle.29 Let U M ( x i ) and U 2 M ( x i ) be the approximate numerical solutions (in the computational domain [ x min , x max ] ) obtained with M and 2 M mesh intervals, respectively. Also let
Ω M = x i : x i = x min + ( i 1 ) h , 1 i M .
where h = x max x min M 1 . The maximum error and the rate of convergence are determined by the double-mesh differences
E M = max x i Ω M | U M ( x i ) U 2 M ( x i ) | , ()
and
q = log 2 E M E 2 M . ()

The numerical values of the European and American passport option for the nonsymmetric case, using all the three schemes are tabulated (for various accumulated gains) in Tables 3 and 4, respectively, with the parameters being taken to be S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , and T t = 2 .3 The loglog plot of the maximum error against various spatial steps, as given by (56) are presented in Figure 2. Finally, the maximum error, the rate of convergence and the CPU time for the nonsymmetric case using the CNIM, HOC and HOCGS are given in Tables 5 and 6, respectively.

Details are in the caption following the image
Loglog plot of maximum error against M for the European passport option with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , and N = 800 with ξ = 13
TABLE 3. Price of the European passport option with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , M = 800 , and N = 800 with ξ = 13
w CNIM HOC HOCGS
20 10.428911 10.430595 10.430803
10 13.509960 13.512246 13.512163
5 15.357743 15.360405 15.360103
2 16.577444 16.580551 16.579883
1 17.003622 17.006314 17.006092
0 17.439919 17.440792 17.442332
1 17.886523 17.889334 17.889046
2 18.343627 18.347030 18.346170
5 19.778782 19.781776 19.781271
10 22.372380 22.374982 22.374694
20 28.226310 28.228299 28.228294
TABLE 4. Price of the American passport option with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , M = 800 , and N = 800 with ξ = 13
w CNIM HOC HOCGS
20 10.612413 10.614219 10.613976
10 13.787373 13.789847 13.789170
5 15.700414 15.703318 15.702323
2 16.967035 16.970438 16.968990
1 17.410351 17.413314 17.412324
0 17.864595 17.865597 17.866500
1 18.330000 18.333108 18.332004
2 18.806809 18.810562 18.808815
5 20.306628 20.309958 20.308561
10 23.027069 23.030020 23.028786
20 28.551988 29.213696 29.212595
TABLE 5. Maximum error, rate of convergence and CPU time for the European passport option with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , and N = 800 with ξ = 13
Spatial nodes 21 41 81 161
CNIM error 3.692374 1.218312 0.279163 0.053758
CNIM order - 1.599666 2.125705 2.376550
CPU time (s) 0.090000 0.090000 0.310000 0.450000
HOC error 2.904958 0.871569 0.194817 0.033796
HOC order - 1.736830 2.161497 2.527194
CPU time (s) 0.290000 1.830000 4.480000 28.59000
HOCGS error 0.429031 0.153247 0.035894 0.004895
HOCGS order - 1.485222 2.094036 2.874414
CPU time (s) 0.320000 2.210000 5.850000 38.76000
TABLE 6. Maximum error, rate of convergence and CPU time for the American passport option with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , and N = 800 with ξ = 13
Spatial nodes 21 41 81 161
CNIM error 3.692747 1.238479 0.284755 0.054978
CNIM order - 1.576126 2.120778 2.372786
CPU time (s) 0.090000 0.090000 0.460000 0.540000
HOC error 2.864784 0.859610 0.186518 0.029594
HOC order - 1.736673 2.204366 2.655934
CPU time (s) 0.270000 1.760000 4.500000 27.99000
HOCGS error 0.003617 0.004003 0.000790 0.000110
HOCGS ORDER - −0.146441 2.341362 2.841505
CPU time (s) 0.330000 2.050000 5.820000 36.82000

In order to observe the maximum error and rate of convergence with respect to grid stretching parameter ξ , we present the numerical results for both the symmetric and nonsymmetric case, for several grid stretching parameters ξ , in Tables 7 and 8, respectively, for various number of spatial steps.

TABLE 7. Maximum error and rate of convergence of the European passport option for various values of ξ and M, with S ( t ) = 100 , r = 0 % , γ = 0 % , σ = 30 % , T t = 1 , and N = 800
ξ M=21 M=41 M=81 M=161 M=321
1 0.858980 0.217465 0.054529 0.013642 0.003411
1.981842 1.995687 1.998968 1.999916
2 0.393637 0.099603 0.024972 0.006247 0.001562
1.982607 1.995885 1.999085 2.000152
3 0.262586 0.059071 0.014811 0.003705 0.000926
2.152258 1.995776 1.999125 2.000421
4 0.316357 0.072677 0.013157 0.002502 0.000625
2.121981 2.465625 2.394758 2.000752
5 0.360326 0.084606 0.015630 0.002408 0.000456
2.090476 2.436402 2.698680 2.400214
6 0.397625 0.094951 0.017826 0.002774 0.000391
2.066148 2.413170 2.684078 2.827118
7 0.430080 0.104107 0.019807 0.003108 0.000439
2.046534 2.394007 2.671740 2.822355
8 0.458848 0.112334 0.021614 0.003417 0.000485
2.030222 2.377773 2.661075 2.817996
9 0.484714 0.119814 0.023278 0.003704 0.000527
2.016338 2.363740 2.651695 2.814002
10 0.508230 0.126679 0.024823 0.003973 0.000566
2.004303 2.351414 2.643332 2.810328
11 0.529804 0.133029 0.026266 0.004226 0.000604
1.993717 2.340450 2.635792 2.806933
12 0.549744 0.138940 0.027622 0.004465 0.000639
1.984296 2.330594 2.628933 2.803781
13 0.568289 0.144473 0.028900 0.004692 0.000673
1.975826 2.321656 2.622644 2.800841
14 0.585628 0.149675 0.030111 0.004909 0.000706
1.968147 2.313491 2.616842 2.798089
15 0.601915 0.154587 0.031261 0.005115 0.000737
1.961136 2.305983 2.611457 2.795503
TABLE 8. Maximum error and rate of convergence of the European passport option for various values of ξ and M, with S ( t ) = 100 , r = 5 % , γ = 4 . 5 % , σ = 30 % , T t = 2 , and N = 800
ξ M=21 M=41 M=81 M=161
1 0.658137 0.143690 0.026107 0.006971
2.195429 2.460436 1.905090
2 0.252002 0.059186 0.014014 0.003056
2.090101 2.078355 2.197110
3 0.269837 0.077166 0.013052 0.002396
1.806046 2.563666 2.445724
4 0.303693 0.090864 0.016459 0.002862
1.740837 2.464800 2.523634
5 0.329496 0.101962 0.019449 0.003191
1.692228 2.390271 2.607718
6 0.349808 0.111354 0.022124 0.003498
1.651409 2.331468 2.661031
7 0.366531 0.119434 0.024553 0.003767
1.617722 2.282261 2.704571
8 0.380658 0.126579 0.026782 0.003973
1.588455 2.240695 2.753014
9 0.393092 0.132907 0.028847 0.004180
1.564453 2.203930 2.786737
10 0.403794 0.138755 0.030772 0.004379
1.541075 2.172835 2.812973
11 0.413034 0.143960 0.032579 0.004546
1.520596 2.143658 2.841175
12 0.421538 0.148877 0.034282 0.004724
1.501543 2.118600 2.859329
13 0.429031 0.153247 0.035894 0.004895
1.485222 2.094036 2.874414
14 0.436074 0.157517 0.037426 0.004989
1.469064 2.073388 2.907113
15 0.442243 0.161376 0.038886 0.005182
1.454413 2.053086 2.907717

5 CONCLUSION

We consider the problem of pricing the passport option for both the symmetric case as well as the nonsymmetric case through HOC schemes in order to obtain better results on a compact stencil. The HOC scheme applied on the nonlinear pricing PDE with non-smooth coefficients resulted in improved results as compared to the CNIM, for the symmetric case with known pricing formula. However, the advantage of the HOC schemes turned out to be much more significant with close to third order accuracy being achieved with the introduction of grid stretching near the zero accumulated wealth level. In fact, the results obtained through grid stretching show a very close match for the analytic solution for the symmetric case. Further, it was observed that the maximum error was also significantly reduced with the introduction of grid stretching. Similar results with regards to accuracy and maximum error was observed for the nonsymmetric case also, using the double-mesh differences for the error.

ACKNOWLEDGMENTS

The first author is grateful to Indian Institute of Technology Guwahati for the Assistantship provided to pursue his Ph.D. The authors express their gratitude to both the Referees for their comments and suggestions.

    CONFLICT OF INTEREST

    This work does not have any conflicts of interest.

    Biographies

    • Ankur Kanaujiya has been a faculty at the National Institute of Technology Rourkela, since 2020. He earned a doctorate degree in Mathematics from the Indian Institute of Technology Guwahati. His area of interest is Computational Finance. He has worked as assistant professor under Technical Education Quality Improvement Programme (TEQIP-III), a World Bank assisted project implemented by the National Project Implementation Unit (NPIU), at Birla Institute of Technology Mesra, Ranchi.

    • Siddhartha P. Chakrabarty is a professor in Mathematics and Data Science & Artificial Intelligence at the Indian Institute of Technology Guwahati. His research areas include Mathematical Finance and Mathematical Biology. He has supervised more than 40 students, including 4 Ph.D. students and is a recipient of several grants and awards, he is actively involved in service and outreach activities, including organizing professional events. His diverse teaching experience includes MOOC courses.

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