possible bug in convert pricer: when notional is not 100

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possible bug in convert pricer: when notional is not 100

P Nelnik
It seems that in the convertible bond pricer,
the coupons paid ignore the 'redemption' input and assume that the redemption is 100
 
So if we have zero interest rate, a coupon of 10% paid with a redeption of 1000 units of currency in a 1 year convert,
with a very low convertion ratio,
then I would expect a value of 1100 units of currency.
But in fact I get (approximately) 1010 units of currency.
i.e. the 10% coupon has been paid on a notional of 100,
even though I specified it to be 1000 rather than 100.
 
Perhpas this isn't a bug it is a 'feature' ?
 
To see this in action, I've made a few small changes to the ConvertibleBond example:
 
 
 
 // the only header you need to use QuantLib
#include <ql/quantlib.hpp>
#ifdef BOOST_MSVC
/* Uncomment the following lines to unmask floating-point
   exceptions. Warning: unpredictable results can arise...
   See http://www.wilmott.com/messageview.cfm?catid=10&threadid=9481
   Is there anyone with a definitive word about this?
*/
// #include <float.h>
// namespace { unsigned int u = _controlfp(_EM_INEXACT, _MCW_EM); }
#endif
#include <boost/timer.hpp>
#include <iostream>
#include <iomanip>
#define LENGTH(a) (sizeof(a)/sizeof(a[0]))
using namespace QuantLib;
#if defined(QL_ENABLE_SESSIONS)
namespace QuantLib {
    Integer sessionId() { return 0; }
}
#endif

int main(int, char* []) {
    try {
        boost::timer timer;
        std::cout << std::endl;
        Option::Type type(Option::Put);
        Real underlying        = 100.0;
        Real spreadRate        = 0.000;
        Spread dividendYield   = 0.00;
        Rate riskFreeRate      = 0.00;
        Volatility volatility  = 0.01;
        Integer settlementDays = 1;
        Integer length         = 1;
        Real redemption        = 1000.0;
        Real conversionRatio   = 0.01 * redemption/underlying; // 2 * at the money
        // set up dates/schedules
        Calendar calendar = TARGET();
        Date today = calendar.adjust(Date::todaysDate());
        Settings::instance().evaluationDate() = today;
        Date settlementDate = calendar.advance(today, settlementDays, Days);
        Date exerciseDate = calendar.advance(settlementDate, length, Years);
        Date issueDate = calendar.advance(exerciseDate, -length, Years);
        BusinessDayConvention convention = ModifiedFollowing;
        Frequency frequency = Annual;
        Schedule schedule(issueDate, exerciseDate,
                          Period(frequency), calendar,
                          convention, convention,
                          DateGeneration::Backward, false);
        DividendSchedule dividends;
        CallabilitySchedule callability;
        std::vector<Real> coupons(1, 0.1); // a 10% coupon
        DayCounter bondDayCount = Thirty360();
/* no callability
  Integer callLength[] = { 1 };  // just one call date at maturity
        Integer putLength[] = {  }; // no put date
        Real callPrices[] = { 101.5, 100.85 };
        Real putPrices[]= { 105.0 };
        // Load call schedules
        for (Size i=0; i<LENGTH(callLength); i++) {
            callability.push_back(
                   boost::shared_ptr<Callability>(
                       new SoftCallability(Callability::Price(
                                                   callPrices[i],
                                                   Callability::Price::Clean),
                                           schedule.date(callLength[i]),
                                           1.20)));
        }
        for (Size j=0; j<LENGTH(putLength); j++) {
            callability.push_back(
                   boost::shared_ptr<Callability>(
                           new Callability(Callability::Price(
                                                   putPrices[j],
                                                   Callability::Price::Clean),
                                           Callability::Put,
                                           schedule.date(putLength[j]))));
        }
*/
        // Assume dividends are paid every 6 months, but here they are zero.
        for (Date d = today + 6*Months; d < exerciseDate; d += 6*Months) {
            dividends.push_back(
                      boost::shared_ptr<Dividend>(new FixedDividend(0, d)));
        }
        DayCounter dayCounter = Actual365Fixed();
        Time maturity = dayCounter.yearFraction(settlementDate,
                                                exerciseDate);
        std::cout << "option type = "  << type << std::endl;
        std::cout << "Time to maturity = "        << maturity
                  << std::endl;
        std::cout << "Underlying price = "        << underlying
                  << std::endl;
        std::cout << "Risk-free interest rate = " << io::rate(riskFreeRate)
                  << std::endl;
        std::cout << "Dividend yield = " << io::rate(dividendYield)
                  << std::endl;
        std::cout << "Volatility = " << io::volatility(volatility)
                  << std::endl;
        std::cout << std::endl;
        std::string method;
        std::cout << std::endl ;
        // write column headings
        Size widths[] = { 35, 14, 14 };
        Size totalWidth = widths[0] + widths[1] + widths[2];
        std::string rule(totalWidth, '-'), dblrule(totalWidth, '=');
        std::cout << dblrule << std::endl;
        std::cout << "Tsiveriotis-Fernandes method" << std::endl;
        std::cout << dblrule << std::endl;
        std::cout << std::setw(widths[0]) << std::left << "Tree type"
                  << std::setw(widths[1]) << std::left << "European"
                  << std::setw(widths[1]) << std::left << "American"
                  << std::endl;
        std::cout << rule << std::endl;
        boost::shared_ptr<Exercise> exercise(
                                          new EuropeanExercise(exerciseDate));
        boost::shared_ptr<Exercise> amExercise(
                                          new AmericanExercise(settlementDate,
                                                               exerciseDate));
        Handle<Quote> underlyingH(
            boost::shared_ptr<Quote>(new SimpleQuote(underlying)));
        Handle<YieldTermStructure> flatTermStructure(
            boost::shared_ptr<YieldTermStructure>(
                new FlatForward(settlementDate, riskFreeRate, dayCounter)));
        Handle<YieldTermStructure> flatDividendTS(
            boost::shared_ptr<YieldTermStructure>(
                new FlatForward(settlementDate, dividendYield, dayCounter)));
        Handle<BlackVolTermStructure> flatVolTS(
            boost::shared_ptr<BlackVolTermStructure>(
                new BlackConstantVol(settlementDate, calendar,
                                     volatility, dayCounter)));

        boost::shared_ptr<BlackScholesMertonProcess> stochasticProcess(
                              new BlackScholesMertonProcess(underlyingH,
                                                            flatDividendTS,
                                                            flatTermStructure,
                                                            flatVolTS));
        Size timeSteps = 801;
        Handle<Quote> creditSpread(
                       boost::shared_ptr<Quote>(new SimpleQuote(spreadRate)));
        boost::shared_ptr<Quote> rate(new SimpleQuote(riskFreeRate));
        Handle<YieldTermStructure> discountCurve(
                boost::shared_ptr<YieldTermStructure>(
                    new FlatForward(today, Handle<Quote>(rate), dayCounter)));
        boost::shared_ptr<PricingEngine> engine(
                  new BinomialConvertibleEngine<JarrowRudd>(stochasticProcess,
                                                            timeSteps));
        ConvertibleFixedCouponBond europeanBond(
                            exercise, conversionRatio, dividends, callability,
                            creditSpread, issueDate, settlementDays,
                            coupons, bondDayCount, schedule, redemption);
        europeanBond.setPricingEngine(engine);
        ConvertibleFixedCouponBond americanBond(
                          amExercise, conversionRatio, dividends, callability,
                          creditSpread, issueDate, settlementDays,
                          coupons, bondDayCount, schedule, redemption);
        americanBond.setPricingEngine(engine);
        method = "Jarrow-Rudd";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                  new BinomialConvertibleEngine<JarrowRudd>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                  new BinomialConvertibleEngine<JarrowRudd>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Cox-Ross-Rubinstein";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
           new BinomialConvertibleEngine<CoxRossRubinstein>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
           new BinomialConvertibleEngine<CoxRossRubinstein>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Additive equiprobabilities";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                   new BinomialConvertibleEngine<AdditiveEQPBinomialTree>(
                                                            stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                   new BinomialConvertibleEngine<AdditiveEQPBinomialTree>(
                                                            stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Trigeorgis";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                  new BinomialConvertibleEngine<Trigeorgis>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                  new BinomialConvertibleEngine<Trigeorgis>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Tian";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                        new BinomialConvertibleEngine<Tian>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                        new BinomialConvertibleEngine<Tian>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Leisen-Reimer";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                new BinomialConvertibleEngine<LeisenReimer>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                new BinomialConvertibleEngine<LeisenReimer>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        method = "Joshi";
        europeanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                      new BinomialConvertibleEngine<Joshi4>(stochasticProcess,
                                                            timeSteps)));
        americanBond.setPricingEngine(boost::shared_ptr<PricingEngine>(
                      new BinomialConvertibleEngine<Joshi4>(stochasticProcess,
                                                            timeSteps)));
        std::cout << std::setw(widths[0]) << std::left << method
                  << std::fixed
                  << std::setw(widths[1]) << std::left << europeanBond.NPV()
                  << std::setw(widths[2]) << std::left << americanBond.NPV()
                  << std::endl;
        std::cout << dblrule << std::endl;
        Real seconds = timer.elapsed();
        Integer hours = int(seconds/3600);
        seconds -= hours * 3600;
        Integer minutes = int(seconds/60);
        seconds -= minutes * 60;
        std::cout << " \nRun completed in ";
        if (hours > 0)
            std::cout << hours << " h ";
        if (hours > 0 || minutes > 0)
            std::cout << minutes << " m ";
        std::cout << std::fixed << std::setprecision(0)
                  << seconds << " s\n" << std::endl;
        return 0;
    } catch (std::exception& e) {
        std::cerr << e.what() << std::endl;
        return 1;
    } catch (...) {
        std::cerr << "unknown error" << std::endl;
        return 1;
    }
}

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Re: possible bug in convert pricer: when notional is not 100

P Nelnik
Thanks  David.


On Thu, Jul 15, 2010 at 12:17 PM, David Klein <[hidden email]> wrote:
As I mentioned before, I am not really familiar with Quantlib, but I am familiar with convertible bonds.

Where are two different (related) concepts. "Notional" (aka "face value") and "redemption". Convertible bonds are typically quoted on a percent of notional basis, so a bond with a notional of 1,000 and a price of 110 would be worth 1,100 units of currency. Convertible bonds also typically redeem at 100% of notional, so at maturity one receives the coupon plus the notional. What I am guessing is happening in Quantlib is that by changing the redemption to 1,000 you have setup a bond with the following structure:

Notional = 500 (or any other number, not really relevant since the returned price is in percent notional)
Redemption = 1000% (of notional. I.e. a cash amount of 5,000)
Coupon=10% (of notional, I.e. a cash amount of 50)
Present value approximately 1010% (of notional, I.e. a cash amount of 5050, assuming one year to redemption)

So 1010 is the correct value.

P.S. A redemption other than 100% is called a non-par redemption. They are very common for zero coupon CBs, rare otherwise.
P.P.S. Feel free to post reply to the mailing list.



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