Integer, Intent (In)	::	m, n, ldp
Integer, Intent (Inout)	::	ifail
Real (Kind=nag_wp), Intent (In)	::	x(m), s, k, t(n), sigma, r, q
Real (Kind=nag_wp), Intent (Inout)	::	p(ldp,n)
Character (1), Intent (In)	::	calput

C Header Interface

#include <nag.h>

void	s30caf_ (const char calput, const Integer m, const Integer n, const double x[], const double s, const double k, const double t[], const double sigma, const double r, const double q, double p[], const Integer ldp, Integer ifail, const Charlen length_calput)

The routine may be called by the names s30caf or nagf_specfun_opt_binary_con_price.

3 Description

s30caf computes the price of a binary or digital cash-or-nothing option which pays a fixed amount,

K

, at expiration if the option is in-the-money (see Section 2.4 in the S Chapter Introduction). For a strike price,

X

, underlying asset price,

S

, and time to expiry,

T

, the payoff is, therefore,

K

, if

S > X

for a call or

S < X

for a put. Nothing is paid out when this condition is not met.

The price of a call with volatility,

σ

, risk-free interest rate,

r

, and annualised dividend yield,

q

, is

P_{call} = K e^{- r T} Φ (d_{2})

and for a put,

P_{put} = K e^{- r T} Φ (- d_{2})

where

Φ

is the cumulative Normal distribution function,

Φ (x) = \frac{1}{\sqrt{2 π}} \int_{- \infty}^{x} (- y^{2} / 2) d y,

and

d_{2} = \frac{\ln (S / X) + (r - q - σ^{2} / 2) T}{σ \sqrt{T}} .

The option price

P_{i j} = P (X = X_{i}, T = T_{j})

is computed for each strike price in a set

X_{i}

i = 1, 2, \dots, m

, and for each expiry time in a set

T_{j}

j = 1, 2, \dots, n

4 References

Reiner E and Rubinstein M (1991) Unscrambling the binary code Risk 4

5 Arguments

1: $calput$ – Character(1) Input

On entry: determines whether the option is a call or a put.

$calput ='C'$: A call; the holder has a right to buy.
$calput ='P'$: A put; the holder has a right to sell.

Constraint:

calput ='C'

'P'

2: $m$ – Integer Input

On entry: the number of strike prices to be used.

Constraint:

m \geq 1

3: $n$ – Integer Input

On entry: the number of times to expiry to be used.

Constraint:

n \geq 1

4: $x (m)$ – Real (Kind=nag_wp) array Input

On entry:

x (i)

must contain

X_{i}

, the

i

th strike price, for

i = 1, 2, \dots, m

Constraint:

x (i) \geq z ​ and ​ x (i) \leq 1 / z

, where

z = x02amf ()

, the safe range parameter, for

i = 1, 2, \dots, m

5: $s$ – Real (Kind=nag_wp) Input

On entry:

S

, the price of the underlying asset.

Constraint:

s \geq z ​ and ​ s \leq 1.0 / z

, where

z = x02amf ()

, the safe range parameter.

6: $k$ – Real (Kind=nag_wp) Input

On entry: the amount,

K

, to be paid at expiration if the option is in-the-money, i.e., if

s > x (i)

when

calput ='C'

, or if

s < x (i)

when

calput ='P'

, for

i = 1, 2, \dots, m

Constraint:

k \geq 0.0

7: $t (n)$ – Real (Kind=nag_wp) array Input

On entry:

t (i)

must contain

T_{i}

, the

i

th time, in years, to expiry, for

i = 1, 2, \dots, n

Constraint:

t (i) \geq z

, where

z = x02amf ()

, the safe range parameter, for

i = 1, 2, \dots, n

8: $sigma$ – Real (Kind=nag_wp) 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: $r$ – Real (Kind=nag_wp) 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:

r \geq 0.0

10: $q$ – Real (Kind=nag_wp) Input

On entry:

q

, the annual continuous yield rate. Note that a rate of 8% should be entered as

0.08

Constraint:

q \geq 0.0

11: $p (ldp, n)$ – Real (Kind=nag_wp) array Output

On exit:

p (i, j)

contains

P_{i j}

, the option price evaluated for the strike price

x_{i}

at expiry

t_{j}

for

i = 1, 2, \dots, m

and

j = 1, 2, \dots, n

12: $ldp$ – Integer Input

On entry: the first dimension of the array p as declared in the (sub)program from which s30caf is called.

Constraint:

ldp \geq m

13: $ifail$ – Integer Input/Output

On entry: ifail must be set to

0

−1

1

to set behaviour on detection of an error; these values have no effect when no error is detected.

A value of

0

causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of

−1

means that an error message is printed while a value of

1

means that it is not.

If halting is not appropriate, the value

−1

1

is recommended. If message printing is undesirable, then the value

1

is recommended. Otherwise, the value

0

is recommended. When the value $- 1$ or $1$ is used it is essential to test the value of ifail on exit.

On exit:

ifail = 0

unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry

ifail = 0

−1

, explanatory error messages are output on the current error message unit (as defined by x04aaf).

Errors or warnings detected by the routine:

$ifail = 1$: On entry, $calput = ⟨ value ⟩$ was an illegal value.

$ifail = 2$: On entry, $m = ⟨ value ⟩$ .
Constraint: $m \geq 1$ .

$ifail = 3$: On entry, $n = ⟨ value ⟩$ .
Constraint: $n \geq 1$ .

$ifail = 4$: On entry, $x (⟨ value ⟩) = ⟨ value ⟩$ .
Constraint: $x (i) \geq ⟨ value ⟩$ and $x (i) \leq ⟨ value ⟩$ .

$ifail = 5$: On entry, $s = ⟨ value ⟩$ .
Constraint: $s \geq ⟨ value ⟩$ and $s \leq ⟨ value ⟩$ .

$ifail = 6$: On entry, $k = ⟨ value ⟩$ .
Constraint: $k \geq 0.0$ .

$ifail = 7$: On entry, $t (⟨ value ⟩) = ⟨ value ⟩$ .
Constraint: $t (i) \geq ⟨ value ⟩$ .

$ifail = 8$: On entry, $sigma = ⟨ value ⟩$ .
Constraint: $sigma > 0.0$ .

$ifail = 9$: On entry, $r = ⟨ value ⟩$ .
Constraint: $r \geq 0.0$ .

$ifail = 10$: On entry, $q = ⟨ value ⟩$ .
Constraint: $q \geq 0.0$ .

$ifail = 12$: On entry, $ldp = ⟨ value ⟩$ and $m = ⟨ value ⟩$ .
Constraint: $ldp \geq m$ .

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 999$: Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

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 s15abf and s15adf). An accuracy close to machine precision can generally be expected.

8 Parallelism and Performance

s30caf 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 routine. 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 a cash-or-nothing put with a time to expiry of

0.75

years, a stock price of

100

and a strike price of

80

. The risk-free interest rate is

6 %

per year and the volatility is

35 %

per year. If the option is in-the-money at expiration, i.e., if

S > X

, the payoff is

10

s30ca: FL CL CPP AD

NAG FL Interfaces30caf (opt_​binary_​con_​price)

▸▿ Contents

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results

NAG FL Interface
s30caf (opt_binary_con_price)