public override void calculate()
{
Utils.QL_REQUIRE(numericalFix_ == NumericalFix.None || numericalFix_ == NumericalFix.Taylor, () =>
"numerical fix must be None or Taylor");
Utils.QL_REQUIRE(accrualBias_ == AccrualBias.HalfDayBias || accrualBias_ == AccrualBias.NoBias, () =>
"accrual bias must be HalfDayBias or NoBias");
Utils.QL_REQUIRE(forwardsInCouponPeriod_ == ForwardsInCouponPeriod.Flat ||
forwardsInCouponPeriod_ == ForwardsInCouponPeriod.Piecewise, () =>
"forwards in coupon period must be Flat or Piecewise");
// it would be possible to handle the cases which are excluded below,
// but the ISDA engine is not explicitly specified to handle them,
// so we just forbid them too
Actual365Fixed dc = new Actual365Fixed();
Actual360 dc1 = new Actual360();
Actual360 dc2 = new Actual360(true);
Date evalDate = Settings.evaluationDate();
// check if given curves are ISDA compatible
// (the interpolation is checked below)
Utils.QL_REQUIRE(!discountCurve_.empty(), () => "no discount term structure set");
Utils.QL_REQUIRE(!probability_.empty(), () => "no probability term structure set");
Utils.QL_REQUIRE(discountCurve_.link.dayCounter() == dc, () =>
"yield term structure day counter (" + discountCurve_.link.dayCounter() + ") should be Act/365(Fixed)");
Utils.QL_REQUIRE(probability_.link.dayCounter() == dc, () =>
"probability term structure day counter (" + probability_.link.dayCounter() + ") should be "
+ "Act/365(Fixed)");
Utils.QL_REQUIRE(discountCurve_.link.referenceDate() == evalDate, () =>
"yield term structure reference date (" + discountCurve_.link.referenceDate()
+ " should be evaluation date (" + evalDate + ")");
Utils.QL_REQUIRE(probability_.link.referenceDate() == evalDate, () =>
"probability term structure reference date (" + probability_.link.referenceDate()
+ " should be evaluation date (" + evalDate + ")");
Utils.QL_REQUIRE(arguments_.settlesAccrual, () => "ISDA engine not compatible with non accrual paying CDS");
Utils.QL_REQUIRE(arguments_.paysAtDefaultTime, () => "ISDA engine not compatible with end period payment");
Utils.QL_REQUIRE((arguments_.claim as FaceValueClaim) != null, () =>
"ISDA engine not compatible with non face value claim");
Date maturity = arguments_.maturity;
Date effectiveProtectionStart = Date.Max(arguments_.protectionStart, evalDate + 1);
// collect nodes from both curves and sort them
List <Date> yDates = new List <Date>(), cDates = new List <Date>();
var castY1 = discountCurve_.link as PiecewiseYieldCurve <Discount, LogLinear>;
var castY2 = discountCurve_.link as InterpolatedForwardCurve <BackwardFlat>;
var castY3 = discountCurve_.link as InterpolatedForwardCurve <ForwardFlat>;
var castY4 = discountCurve_.link as FlatForward;
if (castY1 != null)
{
if (castY1.dates() != null)
{
yDates = castY1.dates();
}
}
else if (castY2 != null)
{
yDates = castY2.dates();
}
else if (castY3 != null)
{
yDates = castY3.dates();
}
else if (castY4 != null)
{
}
else
{
Utils.QL_FAIL("Yield curve must be flat forward interpolated");
}
var castC1 = probability_.link as InterpolatedSurvivalProbabilityCurve <LogLinear>;
var castC2 = probability_.link as InterpolatedHazardRateCurve <BackwardFlat>;
var castC3 = probability_.link as FlatHazardRate;
if (castC1 != null)
{
cDates = castC1.dates();
}
else if (castC2 != null)
{
cDates = castC2.dates();
}
else if (castC3 != null)
{
}
else
{
Utils.QL_FAIL("Credit curve must be flat forward interpolated");
}
// Todo check
List <Date> nodes = yDates.Union(cDates).ToList();
if (nodes.empty())
{
nodes.Add(maturity);
}
double nFix = (numericalFix_ == NumericalFix.None ? 1E-50 : 0.0);
// protection leg pricing (npv is always negative at this stage)
double protectionNpv = 0.0;
Date d0 = effectiveProtectionStart - 1;
double P0 = discountCurve_.link.discount(d0);
double Q0 = probability_.link.survivalProbability(d0);
Date d1;
int result = nodes.FindIndex(item => item > effectiveProtectionStart);
for (int it = result; it < nodes.Count; ++it)
{
if (nodes[it] > maturity)
{
d1 = maturity;
it = nodes.Count - 1; //early exit
}
else
{
d1 = nodes[it];
}
double P1 = discountCurve_.link.discount(d1);
double Q1 = probability_.link.survivalProbability(d1);
double fhat = Math.Log(P0) - Math.Log(P1);
double hhat = Math.Log(Q0) - Math.Log(Q1);
double fhphh = fhat + hhat;
if (fhphh < 1E-4 && numericalFix_ == NumericalFix.Taylor)
{
double fhphhq = fhphh * fhphh;
protectionNpv +=
P0 * Q0 * hhat * (1.0 - 0.5 * fhphh + 1.0 / 6.0 * fhphhq -
1.0 / 24.0 * fhphhq * fhphh +
1.0 / 120 * fhphhq * fhphhq);
}
else
{
protectionNpv += hhat / (fhphh + nFix) * (P0 * Q0 - P1 * Q1);
}
d0 = d1;
P0 = P1;
Q0 = Q1;
}
protectionNpv *= arguments_.claim.amount(null, arguments_.notional.Value, recoveryRate_);
results_.defaultLegNPV = protectionNpv;
// premium leg pricing (npv is always positive at this stage)
double premiumNpv = 0.0, defaultAccrualNpv = 0.0;
for (int i = 0; i < arguments_.leg.Count; ++i)
{
FixedRateCoupon coupon = arguments_.leg[i] as FixedRateCoupon;
Utils.QL_REQUIRE(coupon.dayCounter() == dc ||
coupon.dayCounter() == dc1 ||
coupon.dayCounter() == dc2, () =>
"ISDA engine requires a coupon day counter Act/365Fixed "
+ "or Act/360 (" + coupon.dayCounter() + ")");
// premium coupons
if (!arguments_.leg[i].hasOccurred(evalDate, includeSettlementDateFlows_))
{
double x1 = coupon.amount();
double x2 = discountCurve_.link.discount(coupon.date());
double x3 = probability_.link.survivalProbability(coupon.date() - 1);
premiumNpv +=
coupon.amount() *
discountCurve_.link.discount(coupon.date()) *
probability_.link.survivalProbability(coupon.date() - 1);
}
// default accruals
if (!new simple_event(coupon.accrualEndDate())
.hasOccurred(effectiveProtectionStart, false))
{
Date start = Date.Max(coupon.accrualStartDate(), effectiveProtectionStart) - 1;
Date end = coupon.date() - 1;
double tstart = discountCurve_.link.timeFromReference(coupon.accrualStartDate() - 1) -
(accrualBias_ == AccrualBias.HalfDayBias ? 1.0 / 730.0 : 0.0);
List <Date> localNodes = new List <Date>();
localNodes.Add(start);
//add intermediary nodes, if any
if (forwardsInCouponPeriod_ == ForwardsInCouponPeriod.Piecewise)
{
foreach (Date node in nodes)
{
if (node > start && node < end)
{
localNodes.Add(node);
}
}
//std::vector<Date>::const_iterator it0 = std::upper_bound(nodes.begin(), nodes.end(), start);
//std::vector<Date>::const_iterator it1 = std::lower_bound(nodes.begin(), nodes.end(), end);
//localNodes.insert(localNodes.end(), it0, it1);
}
localNodes.Add(end);
double defaultAccrThisNode = 0.0;
Date firstnode = localNodes.First();
double t0 = discountCurve_.link.timeFromReference(firstnode);
P0 = discountCurve_.link.discount(firstnode);
Q0 = probability_.link.survivalProbability(firstnode);
foreach (Date node in localNodes.Skip(1)) //for (++node; node != localNodes.Last(); ++node)
{
double t1 = discountCurve_.link.timeFromReference(node);
double P1 = discountCurve_.link.discount(node);
double Q1 = probability_.link.survivalProbability(node);
double fhat = Math.Log(P0) - Math.Log(P1);
double hhat = Math.Log(Q0) - Math.Log(Q1);
double fhphh = fhat + hhat;
if (fhphh < 1E-4 && numericalFix_ == NumericalFix.Taylor)
{
// see above, terms up to (f+h)^3 seem more than enough,
// what exactly is implemented in the standard isda C
// code ?
double fhphhq = fhphh * fhphh;
defaultAccrThisNode +=
hhat * P0 * Q0 *
((t0 - tstart) *
(1.0 - 0.5 * fhphh + 1.0 / 6.0 * fhphhq -
1.0 / 24.0 * fhphhq * fhphh) +
(t1 - t0) *
(0.5 - 1.0 / 3.0 * fhphh + 1.0 / 8.0 * fhphhq -
1.0 / 30.0 * fhphhq * fhphh));
}
else
{
defaultAccrThisNode +=
(hhat / (fhphh + nFix)) *
((t1 - t0) * ((P0 * Q0 - P1 * Q1) / (fhphh + nFix) -
P1 * Q1) +
(t0 - tstart) * (P0 * Q0 - P1 * Q1));
}
t0 = t1;
P0 = P1;
Q0 = Q1;
}
defaultAccrualNpv += defaultAccrThisNode * arguments_.notional.Value *
coupon.rate() * 365.0 / 360.0;
}
}
results_.couponLegNPV = premiumNpv + defaultAccrualNpv;
// upfront flow npv
double upfPVO1 = 0.0;
results_.upfrontNPV = 0.0;
if (!arguments_.upfrontPayment.hasOccurred(
evalDate, includeSettlementDateFlows_))
{
upfPVO1 =
discountCurve_.link.discount(arguments_.upfrontPayment.date());
if (arguments_.upfrontPayment.amount().IsNotEqual(0.0))
{
results_.upfrontNPV = upfPVO1 * arguments_.upfrontPayment.amount();
}
}
results_.accrualRebateNPV = 0.0;
if (arguments_.accrualRebate != null &&
arguments_.accrualRebate.amount().IsNotEqual(0.0) &&
!arguments_.accrualRebate.hasOccurred(evalDate, includeSettlementDateFlows_))
{
results_.accrualRebateNPV =
discountCurve_.link.discount(arguments_.accrualRebate.date()) *
arguments_.accrualRebate.amount();
}
double upfrontSign = 1;
if (arguments_.side == Protection.Side.Seller)
{
results_.defaultLegNPV *= -1.0;
results_.accrualRebateNPV *= -1.0;
}
else
{
results_.couponLegNPV *= -1.0;
results_.upfrontNPV *= -1.0;
}
results_.value = results_.defaultLegNPV + results_.couponLegNPV +
results_.upfrontNPV + results_.accrualRebateNPV;
results_.errorEstimate = null;
if (results_.couponLegNPV.IsNotEqual(0.0))
{
results_.fairSpread =
-results_.defaultLegNPV * arguments_.spread /
(results_.couponLegNPV + results_.accrualRebateNPV);
}
else
{
results_.fairSpread = null;
}
double upfrontSensitivity = upfPVO1 * arguments_.notional.Value;
if (upfrontSensitivity.IsNotEqual(0.0))
{
results_.fairUpfront =
-upfrontSign * (results_.defaultLegNPV + results_.couponLegNPV +
results_.accrualRebateNPV) /
upfrontSensitivity;
}
else
{
results_.fairUpfront = null;
}
if (arguments_.spread.IsNotEqual(0.0))
{
results_.couponLegBPS =
results_.couponLegNPV * Const.BASIS_POINT / arguments_.spread;
}
else
{
results_.couponLegBPS = null;
}
if (arguments_.upfront != null && arguments_.upfront.IsNotEqual(0.0))
{
results_.upfrontBPS =
results_.upfrontNPV * Const.BASIS_POINT / (arguments_.upfront);
}
else
{
results_.upfrontBPS = null;
}
}
