specl: CONDITIONAL/IF-THEN (parser and code)

[rburghol]

@timcera

Overview

• This enables nested IF-THEN-ELSE statements in hsp2.
• Execution should follow an "as appears" in UCI or in hdf5 table (or CSV if applicable)
• Tasks:
  • Parse complicated IF-THEN statement and store in h5/pandas friendly array
  • Add pointer to related IF-THEN in special ACTIONS parser (see specl: ACTIONS (parser and code) #105)
  • Enable UVNAME to facilitate evaluation of IF... (see specl: UVNAME (parser and code) #106 )
  • Develop data model for tokenized runtime object SpecialCondition in om_special_condition.py
  • Add runtime token for parent_ix and sibling_ix in SpecialAction and step_special_action() (see specl: ACTIONS (parser and code) #105)
  • Develop runtime execution step_special_condition() in om_special_condition.py

Data Model

Path and Column Definitions for hdf5

• Path: /SPECACTIONS/conditions
• cond_id: unique integer ID for this condition from parsing
• parent_id: unique integer ID for containing condition if applicable
• sibling_id: unique integer ID for most immediate prior conditions that share the same parent_id i.e. related ELSE statements (will be empty if not nested if/else) -- will only be the related statement that appears before the statement in the UCI
• expression: string representation of conditional (normally as outlined in the UCI, but could be defined in hdf5 or CSV)

Example Table Entry

• Shows a condition that has no parent, no siblings, just a stand-alone IF-THEN block of actions

cond_id	parent_ix	sibling_ix	expression
0	-1	-1	'IF (precx1 > 6.000) THEN'

Code

UCI excerpt (see

Example 1: Adjust infiltration exp under high precip daily total.

***User-Defined Variable Quantity Line
  UVQUAN precx1 PERLND   1 PREC             3                 DY 14 SUM

*** ACTIONS
***optyp range dc ds yr  mo da hr mn d t   vari  s1 s2 s3 ac  value    tc ts num
  <****><-><--><><-><--><-><-><-><-><><>  <----><-><-><-><-><--------> <> <-><->

***Action Lines for INFEXP
IF (precx1 >  6.000) THEN
  PERLND  1                            3  INFEXP          =  8.0000000
ELSE
  PERLND  1                            3  INFEXP          =  2.0000000
END IF

Example 2:

***Action Lines for INFEXP
IF (precx1 >  6.000) THEN
  PERLND  1                            3  INFEXP          =  8.0000000
ELSE
  PERLND  1                            3  INFEXP          =  2.0000000
END IF

Operational model Design:

• Each IF statement will be given it's own state_ix, and it's value will be 1/0 depending on the conditional evaluation at each time step (the step_model() method).
  • ix: Their state_ix value is their definitive active/inactive status
  • parent_ix: They will have an attribute that points to the state_ix of a parent conditional statement if it is nested inside another IF-THEN (this value will be -1 if they are not contained)
  • arg1_ix, arg2_ix, op: They will have attributes that define their input state_ix pointers, and their operator (an integer)
  • $V = AND(C_{self}, C_{p})$; where $C_{self}$ = conditional statement result and $C_{p}$ = parent conditional (if present)
• Sub-conditionals ELSE/ELSE IF:
  • ix: Their state_ix value is their definitive active/inactive status
  • parent_ix: They will have an attribute that points to the state_ix of a parent conditional statement if it is nested inside another IF-THEN (this value will be -1 if they are not contained)
  • sibling_ix: The state_ix index of their prior sibling conditional. (assumes the activity state of the sibling aggregates any/all prior siblings state)
  • Their state_ix ACTIVE status will be the NOR of all previous sibling elements of their conditional tree and their own conditional evaluation.
  • $V = AND(C_{self}, C_{p}, NOR(C_{sibs})$; where $C_{self}$ = conditional statement result and $C_{p}$ = parent conditional (if present) and $C_{sibs}$ = siblings 1 to n value
  • Example:
    • IF an ELSE IF statement is preceded by another ELSE IF and an IF statement,
    • $V = AND(C_{self}, C_{p}, NOT(C_{sib) )$
    • $1 = AND(1, 1, NOT(0) )$
    • $0 = AND(1, 0, NOT(0) )$
    • $0 = AND(1, 1, NOT(1) )$
• All conditional components will be evaluated during the beginning of the step() evaluation (so that changes of state are evaluated in the moment)
• @njit code will check enabled state value and return if enabled == 0 (this should be quite fast, despite evaluating many times)

[rburghol]

IF-THEN multiline parsing:

• From Tim:

words = line.split()
...
words[0] == "IF" or f"{words[0]} {words[1]}" == "ELSE IF":
                    continuation_lines = [" ".join(line.strip().split())]
                    while True:
                        loop_words = continuation_lines[-1].split()
                        if loop_words[-1] == "THEN":
                            continuation_line = " ".join(continuation_lines)
                            break
                        continuation_lines.append(" ".join(line.next().strip().split()))

Testing: Proof of concept.

• Can we send an iter() list to a sub-function that then goes ahead and pops a couple of lines off in order to track a multi-line IF statement?
• Answer: yes. The iterable object is incremented by the called function, and that is reflected by essentially skipping that line when it returns to the original loop.
• Todo: use words method from above
  • words = line.split()
  • Allows us to ask words[0] == "IF" or f"{words[0]} {words[1]}" == "ELSE IF": as opener for a new conditional.

def get_ifs(lines, line, line_end='THEN'):
    end_ln = len(line_end)
    while line[-end_ln:] != line_end:
        nline = next(lines).strip()
        line = line + " " + nline
    return(line)

llines = ["IF h = 1 THEN", "IF k = 4", "AND z = 5", "AND i < 25 THEN", "v = 1", "ELSE IF b = 6 THEN", "ELSE IF v = 2 THEN"]
lines = iter(llines)
n = 0
for line in lines:
    n = n + 1
    line = line.strip()
    if line[0:2] == 'IF':
        l = get_ifs(lines, line )
    else:
        l = line
    print(n, ":", l)

Output:

1 : IF h = 1 THEN
2 : IF k = 4 AND z = 5 AND i < 25 THEN
3 : v = 1
4 : ELSE IF b = 6 THEN
5 : ELSE IF v = 2 THEN