Review Algorithm Property Defaults

[PeterParker]

This issue was originally TRAC 9153

The "Properties" tables generated by WikiMaker expose the fact that for some algorithms we are using rather user-unfriendly conventions to denote various default values.

Examples:

• There are 78 algorithms that use -1. Presumably, there will be some fraction of these where -1 is an acceptable value that can be used by the algorithm, but in most cases they are associated with a "must-be-positive" validator. Andrei has suggested that using -DBL_MAX in such cases might be a viable alternative.
• -1.0 is used by an algorithm to denote an unspecified, default stop time.
• There are 5 algorithms that use -0 as a default.

This problem has become more visible since http://trac.mantidproject.org/mantid/ticket/2480, which populates algorithm dialogs with default values.

A solution to this problem would make documentation a lot clearer, and would hopefully make algorithms easier to understand and use.

[PeterParker]

@PeterParker (2014-03-10T12:14:17):
I offer up the following script to the eventual owner of this ticket, as a quick way to see which algorithms use which default values:

def get_all_prop_defaults():
    """Get prop default information in a form we can use."""
    prop_defaults = {}
    for alg_name in AlgorithmFactory.getRegisteredAlgorithms(True).keys():
        alg = AlgorithmManager.create(alg_name)
        for prop_name in alg.orderedProperties():
            prop = alg.getProperty(prop_name)
            if prop.getDefault in prop_defaults:
                prop_defaults[prop.getDefault][0] += 1
                prop_defaults[prop.getDefault][1].append(str(alg))
            else:
                prop_defaults[prop.getDefault] = [1, [str(alg)], prop_name]
    return prop_defaults

def print_default_usage_table():
    """Prints a table of all default values, how many times they are used, and an example algorithm
    that uses it."""
    table = [["#", "Default", "Example Algorithm"]]

    prop_defaults = get_all_prop_defaults()
    for prop_default in sorted(prop_defaults.keys()):
        table.append([
            prop_defaults[prop_default][0],
            prop_default,
            prop_defaults[prop_default][1]])

    row_format ="{:>5} | {:<35} | {:<50}"
    for row in table:
        print row_format.format(*row)

def print_all_algs_that_use_default_value(default_str):
    """For a given default value, print the names of all the algorithms that have
    properties that use it."""
    prop_defaults = get_all_prop_defaults()

    try:
        algs = prop_defaults[default_str][1]
    except:
        print "No properties exist with a default value of %s." % default_str
    else:
        print "The following algorithms contain a property with default value of %s:" % default_str
        for alg in algs:
            print alg
        print

# Uncomment to use:
# print_all_algs_that_use_default_value("#")
# print_default_usage_table()

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@NickDraper (2015-04-27T08:10:35):
Moved to R3.5 at the R3.4 code freeze