Computes a suite of diagnostic values for an MLMC estimation problem.
Arguments
- mlmc_l
a user supplied function which provides the estimate for level \(l\). It must take at least two arguments, the first is the level number to be simulated and the second the number of paths. Additional arguments can be taken if desired: all additional
...
arguments to this function are forwarded to the user definedmlmc_l
function.The user supplied function should return a named list containing one element named
sums
and second namedcost
, where:sums
is a vector of length six \(\left(\sum Y_i, \sum Y_i^2, \sum Y_i^3, \sum Y_i^4, \sum X_i, \sum X_i^2\right)\) where \(Y_i\) are iid simulations with expectation \(E[P_0]\) when \(l=0\) and expectation \(E[P_l-P_{l-1}]\) when \(l>0\), and \(X_i\) are iid simulations with expectation \(E[P_l]\). Note that this differs from the main
mlmc()
driver, which only requires the first two of these elements in order to calculate the estimate. The remaining elements are required bymlmc.test()
since they are used for convergence tests, kurtosis, and telescoping sum checks.cost
is a scalar with the total cost of the paths simulated. For example, in the financial options samplers included in this package, this is calculated as \(NM^l\), where \(N\) is the number of paths requested in the call to the user function
mlmc_l
, \(M\) is the refinement cost factor (\(M=2\) formcqmc06_l()
and \(M=4\) foropre_l()
), and \(l\) is the level being sampled.
See the function (and source code of)
opre_l()
andmcqmc06_l()
in this package for an example of user supplied level samplers.- N
number of samples to use in the tests
- L
number of levels to use in the tests
- N0
initial number of samples which are used for the first 3 levels and for any subsequent levels which are automatically added. Must be \(> 0\).
- eps.v
a vector of one or more target accuracies for the tests. Must all be \(> 0\).
- Lmin
the minimum level of refinement. Must be \(\ge 2\).
- Lmax
the maximum level of refinement. Must be \(\ge\)
Lmin
.- parallel
if an integer is supplied, R will fork
parallel
parallel processes. This is done for the convergence tests section by splitting theN
samples as evenly as possible across cores when sampling each level. This is also done for the MLMC complexity tests by passing theparallel
argument on to themlmc()
driver when targeting each accuracy level ineps
.- silent
set to TRUE to supress running output (identical output can still be printed by printing the return result)
- ...
additional arguments which are passed on when the user supplied
mlmc_l
function is called
Value
An mlmc.test
object which contains all the computed diagnostic values.
This object can be printed or plotted (see plot.mlmc.test
).
Details
See one of the example level sampler functions (e.g. opre_l()
) for example usage.
This function is based on GPL-2 'Matlab' code by Mike Giles.
Author
Louis Aslett <louis.aslett@durham.ac.uk>
Mike Giles <Mike.Giles@maths.ox.ac.uk>
Tigran Nagapetyan <nagapetyan@stats.ox.ac.uk>
Examples
# \donttest{
# Example calls with realistic arguments
# Financial options using an Euler-Maruyama discretisation
tst <- mlmc.test(opre_l, N = 2000000,
L = 5, N0 = 1000,
eps.v = c(0.005, 0.01, 0.02, 0.05, 0.1),
Lmin = 2, Lmax = 6,
option = 1)
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 2e+06 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 1.0196e+01 1.0196e+01 1.6099e+02 1.6099e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 2.1057e-01 1.0422e+01 4.4430e+00 2.0126e+02 1.9684e+01 2.6040e-01 4.0000e+00
#> 2 2.8460e-02 1.0435e+01 1.0631e+00 2.1220e+02 1.2163e+01 2.4768e-01 1.6000e+01
#> 3 5.9612e-03 1.0463e+01 2.7336e-01 2.1619e+02 7.5955e+00 3.4400e-01 6.4000e+01
#> 4 1.8455e-03 1.0452e+01 6.8677e-02 2.1701e+02 6.2612e+00 1.9414e-01 2.5600e+02
#> 5 4.9396e-04 1.0456e+01 1.7247e-02 2.1695e+02 5.9175e+00 5.9511e-02 1.0240e+03
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 2.141832 (exponent for MLMC weak convergence)
#> beta = 1.997038 (exponent for MLMC variance)
#> gamma = 2.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0050 1.0455e+01 4.609e+07 2.963e+09 64.29 19907394 1654097 402588 101803 25802
#> 0.0100 1.0456e+01 8.493e+06 1.845e+08 21.72 4271774 355405 86235 22183
#> 0.0200 1.0449e+01 2.120e+06 4.612e+07 21.76 1066677 88207 21489 5568
#> 0.0500 1.0486e+01 2.395e+05 1.811e+06 7.56 143709 12008 2983
#> 0.1000 1.0371e+01 6.183e+04 4.527e+05 7.32 35312 2629 1000
#>
tst
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 2e+06 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 1.0196e+01 1.0196e+01 1.6099e+02 1.6099e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 2.1057e-01 1.0422e+01 4.4430e+00 2.0126e+02 1.9684e+01 2.6040e-01 4.0000e+00
#> 2 2.8460e-02 1.0435e+01 1.0631e+00 2.1220e+02 1.2163e+01 2.4768e-01 1.6000e+01
#> 3 5.9612e-03 1.0463e+01 2.7336e-01 2.1619e+02 7.5955e+00 3.4400e-01 6.4000e+01
#> 4 1.8455e-03 1.0452e+01 6.8677e-02 2.1701e+02 6.2612e+00 1.9414e-01 2.5600e+02
#> 5 4.9396e-04 1.0456e+01 1.7247e-02 2.1695e+02 5.9175e+00 5.9511e-02 1.0240e+03
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 2.141832 (exponent for MLMC weak convergence)
#> beta = 1.997038 (exponent for MLMC variance)
#> gamma = 2.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0050 1.0455e+01 4.609e+07 2.963e+09 64.29 19907394 1654097 402588 101803 25802
#> 0.0100 1.0456e+01 8.493e+06 1.845e+08 21.72 4271774 355405 86235 22183
#> 0.0200 1.0449e+01 2.120e+06 4.612e+07 21.76 1066677 88207 21489 5568
#> 0.0500 1.0486e+01 2.395e+05 1.811e+06 7.56 143709 12008 2983
#> 0.1000 1.0371e+01 6.183e+04 4.527e+05 7.32 35312 2629 1000
#>
plot(tst)
# Financial options using a Milstein discretisation
tst <- mlmc.test(mcqmc06_l, N = 20000,
L = 8, N0 = 200,
eps.v = c(0.005, 0.01, 0.02, 0.05, 0.1),
Lmin = 2, Lmax = 10,
option = 1)
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 20000 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 9.9752e+00 9.9752e+00 1.9507e+02 1.9507e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 1.8516e-01 1.0320e+01 1.5125e-01 2.0605e+02 4.5448e+01 2.6257e-01 2.0000e+00
#> 2 1.0286e-01 1.0354e+01 4.2899e-02 2.1216e+02 3.0678e+01 1.1259e-01 4.0000e+00
#> 3 5.3252e-02 1.0312e+01 1.1354e-02 2.1187e+02 1.6533e+01 1.5358e-01 8.0000e+00
#> 4 2.8970e-02 1.0798e+01 3.3326e-03 2.2566e+02 1.3345e+01 7.2728e-01 1.6000e+01
#> 5 1.4151e-02 1.0423e+01 8.3526e-04 2.1640e+02 1.3669e+01 6.1601e-01 3.2000e+01
#> 6 7.3986e-03 1.0704e+01 2.2395e-04 2.2544e+02 1.1963e+01 4.3338e-01 6.4000e+01
#> 7 3.4873e-03 1.0387e+01 5.1566e-05 2.1071e+02 9.6595e+00 5.1188e-01 1.2800e+02
#> 8 1.7975e-03 1.0456e+01 1.3383e-05 2.1602e+02 9.6563e+00 1.0901e-01 2.5600e+02
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 0.961837 (exponent for MLMC weak convergence)
#> beta = 1.925465 (exponent for MLMC variance)
#> gamma = 1.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0050 1.0455e+01 1.354e+07 2.949e+09 217.77 11895928 238691 87730 32761 11721 4273 1647 595 200
#> 0.0100 1.0451e+01 3.392e+06 3.596e+08 106.03 2965597 57209 29757 8110 3033 1091 404 144
#> 0.0200 1.0436e+01 8.268e+05 4.809e+07 58.17 733803 14002 5317 2084 757 274 97
#> 0.0500 1.0425e+01 1.300e+05 3.693e+06 28.41 115840 2548 892 317 108 39
#> 0.1000 1.0417e+01 3.399e+04 4.814e+05 14.16 29912 873 224 104 38
#>
tst
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 20000 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 9.9752e+00 9.9752e+00 1.9507e+02 1.9507e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 1.8516e-01 1.0320e+01 1.5125e-01 2.0605e+02 4.5448e+01 2.6257e-01 2.0000e+00
#> 2 1.0286e-01 1.0354e+01 4.2899e-02 2.1216e+02 3.0678e+01 1.1259e-01 4.0000e+00
#> 3 5.3252e-02 1.0312e+01 1.1354e-02 2.1187e+02 1.6533e+01 1.5358e-01 8.0000e+00
#> 4 2.8970e-02 1.0798e+01 3.3326e-03 2.2566e+02 1.3345e+01 7.2728e-01 1.6000e+01
#> 5 1.4151e-02 1.0423e+01 8.3526e-04 2.1640e+02 1.3669e+01 6.1601e-01 3.2000e+01
#> 6 7.3986e-03 1.0704e+01 2.2395e-04 2.2544e+02 1.1963e+01 4.3338e-01 6.4000e+01
#> 7 3.4873e-03 1.0387e+01 5.1566e-05 2.1071e+02 9.6595e+00 5.1188e-01 1.2800e+02
#> 8 1.7975e-03 1.0456e+01 1.3383e-05 2.1602e+02 9.6563e+00 1.0901e-01 2.5600e+02
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 0.961837 (exponent for MLMC weak convergence)
#> beta = 1.925465 (exponent for MLMC variance)
#> gamma = 1.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0050 1.0455e+01 1.354e+07 2.949e+09 217.77 11895928 238691 87730 32761 11721 4273 1647 595 200
#> 0.0100 1.0451e+01 3.392e+06 3.596e+08 106.03 2965597 57209 29757 8110 3033 1091 404 144
#> 0.0200 1.0436e+01 8.268e+05 4.809e+07 58.17 733803 14002 5317 2084 757 274 97
#> 0.0500 1.0425e+01 1.300e+05 3.693e+06 28.41 115840 2548 892 317 108 39
#> 0.1000 1.0417e+01 3.399e+04 4.814e+05 14.16 29912 873 224 104 38
#>
plot(tst)
# }
# Toy versions for CRAN tests
tst <- mlmc.test(opre_l, N = 10000,
L = 5, N0 = 1000,
eps.v = c(0.025, 0.1),
Lmin = 2, Lmax = 6,
option = 1)
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 10000 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 1.0232e+01 1.0232e+01 1.5823e+02 1.5823e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 1.9481e-01 1.0313e+01 4.5620e+00 2.0120e+02 2.1503e+01 1.3030e-01 4.0000e+00
#> 2 3.3953e-02 1.0629e+01 1.0900e+00 2.1325e+02 1.1524e+01 3.1512e-01 1.6000e+01
#> 3 6.7849e-03 1.0348e+01 2.6568e-01 2.0846e+02 8.2740e+00 3.2525e-01 6.4000e+01
#> 4 1.2933e-03 1.0592e+01 6.9911e-02 2.1665e+02 5.9317e+00 2.7516e-01 2.5600e+02
#> 5 1.6629e-03 1.0420e+01 1.7553e-02 2.1756e+02 6.3481e+00 1.9562e-01 1.0240e+03
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 1.845878 (exponent for MLMC weak convergence)
#> beta = 2.000624 (exponent for MLMC variance)
#> gamma = 2.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0250 1.0455e+01 1.348e+06 2.846e+07 21.11 681953 56853 13713 3428
#> 0.1000 1.0429e+01 6.355e+04 4.549e+05 7.16 35700 2963 1000
#>
tst <- mlmc.test(mcqmc06_l, N = 10000,
L = 8, N0 = 1000,
eps.v = c(0.025, 0.1),
Lmin = 2, Lmax = 10,
option = 1)
#>
#> **********************************************************
#> *** Convergence tests, kurtosis, telescoping sum check ***
#> *** using N = 10000 samples ***
#> **********************************************************
#>
#> l ave(Pf-Pc) ave(Pf) var(Pf-Pc) var(Pf) kurtosis check cost
#> ---------------------------------------------------------------------------------------
#> 0 9.9662e+00 9.9662e+00 1.9301e+02 1.9301e+02 0.0000e+00 0.0000e+00 1.0000e+00
#> 1 1.8497e-01 1.0252e+01 1.4717e-01 2.0805e+02 3.5050e+01 1.1762e-01 2.0000e+00
#> 2 1.0443e-01 1.0462e+01 4.2785e-02 2.1483e+02 2.4410e+01 1.2022e-01 4.0000e+00
#> 3 5.4997e-02 1.0541e+01 1.1994e-02 2.1655e+02 1.8253e+01 2.6352e-02 8.0000e+00
#> 4 2.9120e-02 1.0736e+01 3.3241e-03 2.2103e+02 1.4422e+01 1.8669e-01 1.6000e+01
#> 5 1.4115e-02 1.0361e+01 8.3478e-04 2.1369e+02 1.1162e+01 4.3886e-01 3.2000e+01
#> 6 6.9755e-03 1.0358e+01 2.0620e-04 2.1376e+02 1.1453e+01 1.1802e-02 6.4000e+01
#> 7 3.6329e-03 1.0607e+01 5.4272e-05 2.1635e+02 1.1230e+01 2.7890e-01 1.2800e+02
#> 8 1.7866e-03 1.0468e+01 1.3504e-05 2.1960e+02 1.0223e+01 1.5951e-01 2.5600e+02
#>
#> ******************************************************
#> *** Linear regression estimates of MLMC parameters ***
#> ******************************************************
#>
#> alpha = 0.965073 (exponent for MLMC weak convergence)
#> beta = 1.923518 (exponent for MLMC variance)
#> gamma = 1.000000 (exponent for MLMC cost)
#>
#> *****************************
#> *** MLMC complexity tests ***
#> *****************************
#>
#> eps value mlmc_cost std_cost savings N_l
#> -----------------------------------------------------------
#> 0.0250 1.0427e+01 5.301e+05 2.919e+07 55.06 469429 8857 3386 1412 509 172 70
#> 0.1000 1.0350e+01 3.621e+04 4.715e+05 13.02 28934 1000 1000 95 32
#>