NAG CL Interface
s30sac (opt_​asian_​geom_​price)

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1 Purpose

s30sac computes the Asian geometric continuous average-rate option price.

2 Specification

#include <nag.h>
void  s30sac (Nag_OrderType order, Nag_CallPut option, Integer m, Integer n, const double x[], double s, const double t[], double sigma, double r, double b, double p[], NagError *fail)
The function may be called by the names: s30sac, nag_specfun_opt_asian_geom_price or nag_asian_geom_price.

3 Description

s30sac computes the price of an Asian geometric continuous average-rate option for constant volatility, σ, risk-free rate, r, and cost of carry, b (see Kemna and Vorst (1990)). For a given strike price, X, the price of a call option with underlying price, S, and time to expiry, T, is
Pcall = S e (b¯-r) T Φ ( d¯ 1 ) - X e-rT Φ ( d¯ 2 ) ,  
and the corresponding put option price is
Pput = X e-rT Φ (-d¯2) - S e (b¯-r) T Φ (-d¯1) ,  
where
d¯1 = ln(S/X) + (b¯+σ¯2/2) T σ¯ T  
and
d¯2 = d¯1 - σ¯ T ,  
with
σ¯ = σ 3 ,  b¯ = 1 2 (r- σ2 6 ) .  
Φ is the cumulative Normal distribution function,
Φ(x) = 1 2π - x exp(-y2/2) dy .  
The option price Pij=P(X=Xi,T=Tj) is computed for each strike price in a set Xi, i=1,2,,m, and for each expiry time in a set Tj, j=1,2,,n.

4 References

Kemna A and Vorst A (1990) A pricing method for options based on average asset values Journal of Banking and Finance 14 113–129

5 Arguments

1: order Nag_OrderType Input
On entry: the order argument specifies the two-dimensional storage scheme being used, i.e., row-major ordering or column-major ordering. C language defined storage is specified by order=Nag_RowMajor. See Section 3.1.3 in the Introduction to the NAG Library CL Interface for a more detailed explanation of the use of this argument.
Constraint: order=Nag_RowMajor or Nag_ColMajor.
2: option Nag_CallPut Input
On entry: determines whether the option is a call or a put.
option=Nag_Call
A call; the holder has a right to buy.
option=Nag_Put
A put; the holder has a right to sell.
Constraint: option=Nag_Call or Nag_Put.
3: m Integer Input
On entry: the number of strike prices to be used.
Constraint: m1.
4: n Integer Input
On entry: the number of times to expiry to be used.
Constraint: n1.
5: x[m] const double Input
On entry: x[i-1] must contain Xi, the ith strike price, for i=1,2,,m.
Constraint: x[i-1]z ​ and ​ x[i-1] 1 / z , where z = nag_real_safe_small_number , the safe range parameter, for i=1,2,,m.
6: s double Input
On entry: S, the price of the underlying asset.
Constraint: sz ​ and ​s1.0/z, where z=nag_real_safe_small_number, the safe range parameter.
7: t[n] const double Input
On entry: t[i-1] must contain Ti, the ith time, in years, to expiry, for i=1,2,,n.
Constraint: t[i-1]z, where z = nag_real_safe_small_number , the safe range parameter, for i=1,2,,n.
8: sigma double Input
On entry: σ, the volatility of the underlying asset. Note that a rate of 15% should be entered as 0.15.
Constraint: sigma>0.0.
9: r double Input
On entry: r, the annual risk-free interest rate, continuously compounded. Note that a rate of 5% should be entered as 0.05.
Constraint: r0.0.
10: b double Input
On entry: b, the annual cost of carry rate. Note that a rate of 8% should be entered as 0.08.
11: p[m×n] double Output
Note: where P(i,j) appears in this document, it refers to the array element
  • p[(j-1)×m+i-1] when order=Nag_ColMajor;
  • p[(i-1)×n+j-1] when order=Nag_RowMajor.
On exit: P(i,j) contains Pij, the option price evaluated for the strike price xi at expiry tj for i=1,2,,m and j=1,2,,n.
12: fail NagError * Input/Output
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, m=value.
Constraint: m1.
On entry, n=value.
Constraint: n1.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
NE_NO_LICENCE
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.
NE_REAL
On entry, r=value.
Constraint: r0.0.
On entry, s=value.
Constraint: svalue and svalue.
On entry, sigma=value.
Constraint: sigma>0.0.
NE_REAL_ARRAY
On entry, t[value]=value.
Constraint: t[i]value.
On entry, x[value]=value.
Constraint: x[i]value and x[i]value.

7 Accuracy

The accuracy of the output is dependent on the accuracy of the cumulative Normal distribution function, Φ. This is evaluated using a rational Chebyshev expansion, chosen so that the maximum relative error in the expansion is of the order of the machine precision (see s15abc and s15adc). An accuracy close to machine precision can generally be expected.

8 Parallelism and Performance

s30sac is threaded by NAG for parallel execution in multithreaded implementations of the NAG Library.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this function. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

None.

10 Example

This example computes the price of an Asian geometric continuous average-rate put with a time to expiry of 3 months, a stock price of 80 and a strike price of 85. The risk-free interest rate is 5% per year, the cost of carry is 8% and the volatility is 20% per year.

10.1 Program Text

Program Text (s30sace.c)

10.2 Program Data

Program Data (s30sace.d)

10.3 Program Results

Program Results (s30sace.r)