Quantlib Slow valuation of ois_swap on multiple eval days

Question

I have bootstrapped a curve using several depo and swap rates and am trying to use that curve to get the NPV of a swap over a period of time. The generation of prices iteratively through time is incredibly slow. Given that i'm only pricing over a 4 month period I wouldn't expect it to take 30 minutes. Am I doing something silly here? I saw a previous post commenting on a bug in the SWIG wrapper from python to c++, but according to one of the project maintainers it was patched years ago. See the below:

test_curve.referenceDate() == Date(4,1,2023)

Engine creation

ts = ql.RelinkableYieldTermStructureHandle()
yts.linkTo(test_curve)
engine = ql.DiscountingSwapEngine(yts)

Swap Definition and Creation

swapTenor = ql.Period('1Y')
overnightIndex = ql.Sofr(yts)
fixedRate = 0.01
ois_swap = ql.MakeOIS(swapTenor, overnightIndex, fixedRate, pricingEngine=engine, discountingTermStructure=yts)

NPV Generation

    new_prices = []

instance = ql.Settings.instance()

start_date = ql.Date(1,1,2024)
success_counter = 0

while date < start_date:
    # Update eval date in sim
    instance.evaluationDate = date
    price = ois_swap.NPV()
    new_prices.append(price)

    # Increment date forward
    date += ql.Period('1D')
    new_curve = test_model.get_curve_by_date(date.to_date().strftime('%Y-%m-%d'))

    count = 0

    # Check for new_curve to exist
    while new_curve is None:
        date += ql.Period('1D')
        new_curve = test_model.get_curve_by_date(date.to_date().strftime('%Y-%m-%d'))

        count += 1
        if count == 100:
            break
    yts.linkTo(new_curve)
    engine = ql.DiscountingSwapEngine(yts)
    overnightIndex = ql.Sofr(yts)
    ois_swap = ql.MakeOIS(swapTenor, overnightIndex, fixedRate, pricingEngine=engine, discountingTermStructure=yts, effectiveDate=ql.Date(2,1,2024))

The maturity date on the swap is set to May 2024. Thanks!

Answer 1

After reading the documentation more closely and some scenario testing, I was able to determine that ql.Settings.instance().evaluationDate = date was the culprit. It seems that updating the evaluationdate causes a refresh of ALL instantiated objects within QuantLib that are related to that evaluationDate. I had instantiated a dataframe within my test_model class and pre-built all of the bootstrapped curves I was intending to use, which resulted in the creation of many swap and depo helper objects, all of which would be updated on the evaluationDate change.

For added color: Python destroys objects when their reference counter reaches 0. So, I simply made all of these objects transient within event loop so that I am incrementing, at most, 1 curve and 1 swap object at each step forward. The solution is not lightning fast, since I am bootstrapping a curve at each step, but it's working.

while date < effectiveDate:
    instance.evaluationDate = date

    curve = bootstrap_model.get_curve_by_date(date.to_date().strftime('%Y-%m-%d'), depo=True, swaps=True)

    if curve is None:
        date += ql.Period('1D')
    else:
        yts = ql.RelinkableYieldTermStructureHandle()
        yts.linkTo(curve)
        engine = ql.DiscountingSwapEngine(yts)

        overnightIndex = ql.Sofr(yts)

        ois_swap = ql.MakeOIS(swapTenor, overnightIndex, fixedRate, pricingEngine=engine, discountingTermStructure=yts, effectiveDate=effectiveDate)
        swap_price = ois_swap.NPV()
        new_prices.append(swap_price)