yawnoc / sfta Goto Github PK

• Version: v0.2.5 (24d0017)
• Input ft.txt:

  Event: A    
  - probability: 0.1
  
  Event: B    
  - probability: 0.3
  
  Event: C    
  - probability: 0.5
  
  Event: D    
  - probability: 0.823
  
  Event: DDD   
  - probability: 0.823
  
  Event: CCC   
  - probability: 0.5
  
  Event: BBB   
  - probability: 0.3
  
  Event: AAA   
  - probability: 0.1
  
  Gate: Ascending
  - type: AND
  - inputs: A, B, C, D
  
  Gate: Descending
  - type: AND
  - inputs: AAA, BBB, CCC, DDD
  
  Gate: Top
  - type: OR
  - inputs: Ascending, Descending

• Output ft.txt.out/cut-sets/Top.tsv:

  quantity_type	quantity_value	quantity_unit	cut_set
  probability	0.01235	1	DDD.CCC.BBB.AAA
  probability	0.01234	1	A.B.C.D

• Expected behaviour: cut sets DDD.CCC.BBB.AAA and A.B.C.D have equal probability
• Observed behaviour: cut sets DDD.CCC.BBB.AAA and A.B.C.D have unequal probability (0.01234 ≠ 0.01235)

The observed unequal probability appears to be caused by the floating point multiplication being performed in the order that the underlying events are declared:

>>> # A.B.C.D
>>> 0.1 * 0.3 * 0.5 * 0.823
0.012344999999999998

>>> # DDD.CCC.BBB.AAA
>>> 0.823 * 0.5 * 0.3 * 0.1
0.012345