A simple utility for Phantasy Star Online 2 (PSO2) to calculate the overall success rate of upslotting a weapon/unit to N slots from N-1.

upslot.py

#!/usr/bin/env python3
"""
A simple utility for Phantasy Star Online 2 to calculate the overall success
rate of upslotting a weapon/unit to N slots from N-1.

Can also take number of (filled) S-Grade Augment slots (aka SSA slots) which,
when present, always improve the overall chance (because they are 100% even
on upslot).

Specifying additional boosts (e.g. boost week) and/or manually specifying the
augmentation aid to use is also possible.

For example, to calculate the chance of upslotting a 7s trailblazer (aka
lightstream) weapon with 3 filled SGA slots during 10% boost week while
using a 45% augmentation aid:

    # ./upslot.py -b .1 -a .45 8 3
    Base success rate per slot: 40.0%
    Using 45.00% aid
    Success rate per slot: 85.00%
    Success probabilities:
     8 : 44.371%
     7 : 39.150%
     6 : 13.818%
     5 : 2.4384%
     4 : 0.21516%
     3 : 0.0075938%

That is, a 44% chance to end up with an 8 slots (i.e. total success), a 39%
chance to end up with 7 slots (1 failure), etc. etc.
"""


from decimal import *
import math


TARGET_SUCCESS = [
    Decimal("1.0"),
    Decimal("0.9"),
    Decimal("0.85"),
    Decimal("0.7"),
    Decimal("0.6"),
    Decimal("0.55"),
    Decimal("0.4"),
    Decimal("0.3")
]


def clamp(rate):
    if rate > Decimal("1.0"):
        return Decimal("1.0")
    return rate


def choose_aid(success_rate):
    gap = Decimal("1.0") - success_rate
    if gap == Decimal("0.0"):
        return Decimal("0.0")
    elif gap <= Decimal("0.1"):
        return Decimal("0.1")
    elif gap <= Decimal("0.3"):
        return Decimal("0.3")
    else:
        return Decimal("0.4")

    
def main(target_slots, sga_slots=0, boost='0', aid=None):
    if target_slots < 0 or target_slots > 8:
        raise ValueError('target_slots must be in range [0,8]')
    if sga_slots < 0 or sga_slots >= target_slots:
        raise ValueError('sga_slots must be in range [0,target_slots)')

    boost_week = Decimal(boost)
    base_success = clamp(TARGET_SUCCESS[target_slots - 1] + boost_week)

    if aid is None:
        aid = choose_aid(base_success)
    else:
        aid = Decimal(aid)
    success_rate = clamp(base_success + aid)

    failure_rate = Decimal("1.0") - success_rate

    print(f'Base success rate per slot: {base_success * Decimal("100")}%')
    print(f'Using {aid * Decimal("100")}% aid')
    print(f'Success rate per slot: {success_rate * Decimal("100")}%')

    num_slots = target_slots - sga_slots

    print('Success probabilities:')
    for successes in range(num_slots, -1, -1):
        failures = num_slots - successes

        prob = success_rate ** successes
        if failures > 0:
            prob *= failure_rate ** failures
        prob *= math.comb(num_slots, successes)

        with localcontext() as ctxt:
            ctxt.prec = 5
            print(f' {successes + sga_slots} : {prob * Decimal("100")}%')


        if success_rate == Decimal("1"):
            break


if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser(description='calculate upslot probabilities')
    parser.add_argument('target-slots', type=int,
                        help='target slots')
    parser.add_argument('sga-slots', type=int, nargs='?',
                        default=0,
                        help='number of SGA slots')
    parser.add_argument('--boost', '-b', type=str,
                        default='0',
                        help='additional boosts (e.g. boost week)')
    parser.add_argument('--aid', '-a', type=str,
                        default=None,
                        help='manual augmentation aid specification')
    args = vars(parser.parse_args())

    main(args['target-slots'], sga_slots=args['sga-slots'], boost=args['boost'],
         aid=args['aid'])