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Re: TermStructure->times()

Posted by net316 on Jan 30, 2015; 12:50pm
URL: http://quantlib.414.s1.nabble.com/TermStructure-times-tp16189p16208.html

Peter,
I am currently doing CVA for the whole of our portfolio . I am not using co-terminal swaptions . I use a more representative surface- like this example http://letianwang.net/Codes/HW_Calibration.htm
Is this incorrect ?
Also can you please point me some paper/ method that shows me how I can adjust HW parameters to convert them from the risk-neutral to real-world measure
Thank you very much.


> On Jan 23, 2015, at 4:50 PM, "Ghorpadkar, Suhas" <[hidden email]> wrote:
>
> Thanks. Since my immediate need is CVA, I will put the PFE question on the backburner :)
> So my plan is, calibrate HW for 2 sets of curves (OIS and forecasting) and 1 set of coterminal swaptions, giving me 2 sets of HW parameters.
> For each simulation, generate both the curves based on HW model provided discount factors and NPV the swap, calculate the expected exposure and use it to calculate the CVA.
> Thanks for all your help.
>
> -----Original Message-----
> From: Peter Caspers [mailto:[hidden email]]
> Sent: Friday, January 23, 2015 2:29 PM
> To: Ghorpadkar, Suhas
> Cc: [hidden email]
> Subject: Re: [Quantlib-users] TermStructure->times()
>
> with a high chance that others correct me, I'd say yes for the CVA of
> the underlying 5y swap. For PFE probably not, since dependent on the
> pricing measure, here you'd probably want a physical measure, either
> through historical data or by adjusting the drift in your swaption
> calibrated model (but how ... ?).
> Peter
>
> On 23 January 2015 at 18:21, Ghorpadkar, Suhas
> <[hidden email]> wrote:
>> Thanks.
>> If I am calibrating HW so that I can generate yield curves for a series of future dates to be used in simulation for CVA/PFE and not for pricing Bermudan swaption, do I still restrict my calibration to those 5 coterminal swaptions?
>> Thanks again,
>> Suhas.
>>
>>
>>
>> -----Original Message-----
>> From: Peter Caspers [mailto:[hidden email]]
>> Sent: Friday, January 23, 2015 10:54 AM
>> To: Ghorpadkar, Suhas
>> Cc: [hidden email]
>> Subject: Re: [Quantlib-users] TermStructure->times()
>>
>> As an user I wouldn't care and just trust that the swaption helper
>> returns the times needed in the grid when pricing on a tree -
>> nevertheless, looking in the code the mandatory times of a swaption
>> are the exercise times and the underlying's reset and payment times of
>> both legs. What you should care about more is the steps parameter (30
>> in the example) defining how fine the pricing grid is in the end.
>>
>> For the last question, it is common to calibrate a model for standard
>> bermudan swaptions to the respective european call rights only and use
>> the mean reversion to tune the interplay between these in the model.
>> The Hull White model (also the others in the example) are limited
>> w.r.t. the number of calibration instruments they can replicate, so
>> you have to restrict yourself to the most important ones. With time
>> constant volatility even the five coterminals from the example are too
>> much and will not repriced exactly.
>>
>> Peter
>>
>>
>>
>> On 23 January 2015 at 16:13, Ghorpadkar, Suhas
>> <[hidden email]> wrote:
>>> You are right, there is no call to TermStructure's times() method.
>>> I guess my problem is, I am not sure what SwaptionHelper::addTimesTo() method is returning, is it list of yearfractions for the
>>> Floating leg resets of the underlying swap ?
>>> Also, I am trying to figure out why only "1x5, 2x4, 3x3, 4x2, 5x1" swaptions are considered for calibration? If I have ATM vols for 3x5 swaption,
>>> am not supposed to create a swaptionhelper object for it and ultimately use it in calibration?
>>>
>>> Thanks so much,
>>> Suhas.
>>>
>>> -----Original Message-----
>>> From: Peter Caspers [mailto:[hidden email]]
>>> Sent: Friday, January 23, 2015 3:56 AM
>>> To: Ghorpadkar, Suhas
>>> Cc: [hidden email]
>>> Subject: Re: [Quantlib-users] TermStructure->times()
>>>
>>> as far as I can see in L186 SwaptionHelper::addTimesTo() is used to
>>> fill the times list, which later on the basis for a time grid (L190).
>>> Where do see a call to a term structure's times() method ?
>>> Peter
>>>
>>>
>>> On 22 January 2015 at 22:35, Ghorpadkar, Suhas
>>> <[hidden email]> wrote:
>>>> Hello,
>>>>
>>>>
>>>>
>>>> I am going through the Bermudan swaption example and noticed that when
>>>> calibrating HW, to build TimeGrid, termstructure’s times() method is called.
>>>>
>>>> I am not clear about exactly what this method returns.
>>>>
>>>> Since this is called inside a loop, why would the TermStructure return
>>>> different results for each swaptionhelper?
>>>>
>>>>
>>>>
>>>> Thanks in advance,
>>>>
>>>> Suhas.
>>>>
>>>> ............................................................................
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