 Tag 
Description 
Reference 

 ! 
Tighten resto tolerance if only slightly infeasible 
Section 3.3 in [13] 

 A 
Current iteration is acceptable 
Alternate termination 

 a 
Perturbation for PD singularity impossible, assume singular 
Section 3.1 in [13] 

 C 
Second Order Correction taken 
Section 2.4 in [13] 

 Dh 
Hessian degenerate based on multiple iterations 
Section 3.1 in [13] 

 Dhj 
Hessian/Jacobian degenerate based on multiple iterations 
Section 3.1 in [13] 

 Dj 
Jacobian degenerate based on multiple iterations 
Section 3.1 in [13] 

 dx 
perturbation too large 
Section 3.1 in [13] 

 e 
Cutting back due to evaluation error 
in backtracking line search 

 F 
Filter should be reset, but maximal resets exceeded 
Section 2.3 in [13] 

 F+ 
Resetting filter due to last few rejections of filter 
Section 2.3 in [13] 

 L 
Degenerate Jacobian, already perturbed 
Section 3.1 in [13] 

 l 
Degenerate Jacobian, perturbed 
Section 3.1 in [13] 

 M 
Magic step taken for slack variables 
in backtracking line search 

 Nh 
Hessian not yet degenerate 
Section 3.1 in [13] 

 Nhj 
Hessian/Jacobian not yet degenerate 
Section 3.1 in [13] 

 Nj 
Jacobian not yet degenerate 
Section 3.1 in [13] 

 NW 
Warm start initialization failed 
in Warm Start Initialization 

 q 
PD system possibly singular, attempt improving sol. quality 
Section 3.1 in [13] 

 R 
Solution of restoration phase 
Section 3.3 in [13] 

 S 
PD system possibly singular, accept current solution 
Section 3.1 in [13] 

 s 
PD system singular 
Section 3.1 in [13] 

 s 
Square Problem. Set multipliers to zero 
Default initialization routine 

 Tmax 
Trial is larger than

filter parameter, see (21) in [13] 

 W 
Watchdog line search procedure successful 
Section 3.2 in [13] 

 w 
Watchdog line search procedure unsuccessful, stopped 
Section 3.2 in [13] 

 Wb 
Undoing most recent SR1 update 
Section 5.4.1 in [1] 

 We 
Skip LimitedMemory Update in restoration phase 
Section 5.4.1 in [1] 

 Wp 
Safeguard
for LimitedMemory Update 
Section 5.4.1 in [1] 

 Wr 
Resetting LimitedMemory Update 
Section 5.4.1 in [1] 

 Ws 
Skip LimitedMemory Update since is not positive 
Section 5.4.1 in [1] 

 WS 
Skip LimitedMemory Update since is too small 
Section 5.4.1 in [1] 

 y 
Dual infeasibility, use least square multiplier update 
during ipopt algorithm 

 z 
Apply correction to bound multiplier if too large 
during ipopt algorithm 
