# unstable PS point detected

Dear MG/aMC@NLO experts,

I was testing generation of

p p > mu+ mu- [QCD] @0 ; p p > mu+ mu- j [QCD] @1 ; p p > mu+ mu- j j [QCD] @2

for the UNLOPS matching/merging. Run goes fine but it end with a message

Number of loop ME evaluations (by MadLoop): 3134633

Stability unknown: 0

Stable PS point: 3133011

Unstable PS point (and rescued): 1618

Unstable PS point (and not rescued): 4

Only double precision used: 3133011

Quadruple precision used: 1622

Initialization phase-space points: 1176

Reduction methods used:

> CutTools (double precision) 3125616

> IREGI 7395

> CutTools (quadruple precision) 1618

> Not identified (CTModeRun != -1) 4

Total number of unstable PS point detected: 4 (0.00%)

Maximum fraction of UPS points in channel mu+mu-_

The fraction of unstable PS point is negligible, but still I though it might be worthwhile to report it. Is this expected or is this a bug?

cheers,

Wojciech

## Question information

- Language:
- English Edit question

- Status:
- Open

- Assignee:
- Valentin Hirschi Edit question

- Last query:
- 2015-01-03

- Last reply:
- 2015-01-03

Hi,

Yes this is completely expected, all those rescued means that the problem were solved by using a slower method of computation.

(can be 100 times slower to compute than the normal method).

Valentin might be interested by the fact that you still have 4 point that are not rescued and set to zero.

Cheers,

Olivier

Dear Olivier,

Thanks a lot for looking into this and sorry for not being very precise. What I was worried about are precisely those 4 points you mentioned. The ones that weren't "fixed" by rescue/fallback system.

cheers,

Wojciech

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