Gawron default values inconsistency between duarouter/documentation and duaIterate.py

[jonasjostmann]

The documentation of the duarouter (main/docs/web/docs/duarouter.md) and the script itself (/src/duarouter/RODUAFrame.cpp) use these default values for the Gawron parameters:

Option	Description
--gawron.beta {{DT_FLOAT}}	Use FLOAT as Gawron's beta; default: 0.3
--gawron.a {{DT_FLOAT}}	Use FLOAT as Gawron's a; default: 0.05

The main/tools/assign/duaIterate.py, however, uses 0.5 for the alpha and 0.9 for the beta:

argParser.add_argument("-A", "--gA", type=float, default=.5, help="Sets Gawron's Alpha")
argParser.add_argument("-B", "--gBeta", type=float, default=.9, help="Sets Gawron's Beta")

[namdre]

the values in duaIterate.py were never changed since the initial commit:
22ee2f8#diff-ef9ec561b42078d287fcc807b5d2ce5f00e5239bce86c248ef7e3a456b82f744R91-R94

the values in the C++ code were originally the same and then changed 21 years by a seemingly unrelated commit: 54bf796#diff-eca2ce9e02e8603941ac99a924eac40d71d7aef95b582316c6d9a74329dade9b

I suspect most people use the functionality through duaIterate.py so 0.5 and 0.9 are the more relevant numbers.

[namdre]

Daniel Krajzewicz recalls the reason for the change: Dr. Nils Eissfeldt told him over the phone that those values were better 😄
Daniel is happily using the duaIterate.py defaults along with everyone else, however.

[yunpangfloetteroed]

The beta value, used in Gawron's dissertation, is 0.05 (p. 47), which prevents drivers from remembering forgetting the travel times of routes they have not used for a long time.

The parameter a affects the convergence performance, where a = 0.5, 1 and 2 were used in Gawron's dissertation (p.48). The larger the a, the faster the convergence. Formula (4.17) helps to check if a is desirable.

[namdre]

the somewhat surprising test changes led to the discovery of #14790 and #14791