Using Non-Vectorized Propagation

Here we go over how to use a propagator with the vectorized setting turned off.

Setup

First lets create a RMEMeas object we can interact with and initialize a propagator.

from rmellipse.uobjects import RMEMeas
from rmellipse.propagators import RMEProp
import xarray as xr
import numpy as np

nom = xr.DataArray(
    np.zeros((4, 2)), dims=('d1', 'd2'), coords={'d1': [0, 1, 2, 3], 'd2': np.arange(2)}
)

meas = RMEMeas.from_nom(name='meas', nom=nom)

meas.add_umech(
    name='my_mechanism',
    value=meas.nom + np.ones(meas.nom.shape) * 0.01,
    dof=np.inf,
    category={'Type': 'B', 'Origin': 'Data Sheet'},
)

for i in range(100):
    meas.add_mc_sample(meas.nom + np.random.rand(*meas.nom.shape) * 0.01)

myprop = RMEProp(sensitivity=True, montecarlo_sims=100, verbose=True)

Non-Vectorized Propagation

Sometimes it isn’t possible to vectorize a function. In that case, similar to the non-vectorized version, the inputs and outputs of the function need to be a DataArray for the propagator to recognize the object as being a RMEMeas object. The first dimension of any inputs that were RMEMeas objects will be ‘umech_id’ and the coordinates of that dimension will be the names of the uncertainty mechanism. For non vectorized inputs, the propagator will loop over that first dimension, so the inputs will have a length 1 first dimension called ‘umech_id’. The output should also have that dimension and coordinate.

myprop.settings['montecarlo_sims'] = 0
myprop.settings['sensitivity'] = True
myprop.settings['vectorize'] = False
myprop.settings['verbose'] = False


@myprop.propagate
def add(x, y):
    """Add 2 numbers."""
    output = x + y
    print(x.umech_id.values, output.umech_id.values)
    return output


added = add(meas, 2)

['nominal'] ['nominal']
43a4fe16-67da-487c-8f83-6b02e74a1743 43a4fe16-67da-487c-8f83-6b02e74a1743

Vectorized vs. Unvectorized

By default a RME propagator vectorizes all its functions. This is because vectorized computation is much faster and will save a lot of time, especially with large data sets and large numbers of uncertainty mechanisms. For comparison, here is the same function run once with the vectorize functionality and once without. Note the orders of magnitude increase in run time for the Monte Carlo propagation.

@myprop.propagate
def add2(x):
    return x + 2


myprop.settings['vectorize'] = True
add2(meas)

myprop.settings['vectorize'] = False
add2(meas)

add2 with nominal:
<xarray.DataArray (d1: 4, d2: 2)> Size: 64B
array([[2., 2.],
       [2., 2.],
       [2., 2.],
       [2., 2.]])
Coordinates:
  * d1       (d1) int64 32B 0 1 2 3
  * d2       (d2) int64 16B 0 1