# Long calculation time for subprocesses with 0 xs

Dear experts,

I am trying to generate Z+DM events in Uli Haisch's 2HDM + pseudoscalar model [1].

Generally, I find that it takes very long times O(3 days) to run the subprocess surveys for a single parameter point (pertinent log file at [2], cards I used at [3]). Interestingly, all relevant non-zero contributions seem to be calculated after ~1h. MG5 then spends the remaining ~60h calculating that the remaining subprocesses give 0 contribution. While the exact duration varies, the effect is consistent between different MG5 versions and process definition choices.

Is there a way to speed this up? I imagine one could reduce the required precision for deciding that a subprocess does not contribute.

Any hints would be appreciated.

Thanks

Andreas

[1] Model files at https:/

[2] Log file at https:/

Interesting part is starting at line ~840. There is a madspin crash in

the very end of the log file, but that is unrelated to what I describe here.

[3] Cards at https:/

The "customizecards

respect to the model defaults.

## Question information

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- Answered

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- Last query:
- 2017-10-19

- Last reply:
- 2017-10-20

Hi,

I assume that you are discussing about at LO computation.

In this case, the parameter controlling the zero results are hardcoded

in Source/dsample.f around line 1447, you will see the following:

parameter (max_events=500000) !Maximum # events before get non_zero

reducing such number will return the zero result in a faster way (but less secure way as well).

I would also advise, to check those zero result to ensure that they are indeed returning zero at the first iteration and not at a later stage of the run --which would indicate an issue--.

Cheers,

Olivier

_______

From: <email address hidden> <email address hidden> on behalf of Andreas <email address hidden>

Sent: Thursday, October 19, 2017 4:10 PM

To: Olivier Mattelaer

Subject: [Question #659652]: Long calculation time for subprocesses with 0 xs

New question #659652 on MadGraph5_aMC@NLO:

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Dear experts,

I am trying to generate Z+DM events in Uli Haisch's 2HDM + pseudoscalar model [1].

Generally, I find that it takes very long times O(3 days) to run the subprocess surveys for a single parameter point (pertinent log file at [2], cards I used at [3]). Interestingly, all relevant non-zero contributions seem to be calculated after ~1h. MG5 then spends the remaining ~60h calculating that the remaining subprocesses give 0 contribution. While the exact duration varies, the effect is consistent between different MG5 versions and process definition choices.

Is there a way to speed this up? I imagine one could reduce the required precision for deciding that a subprocess does not contribute.

Any hints would be appreciated.

Thanks

Andreas

[1] Model files at https:/

[2] Log file at https:/

Interesting part is starting at line ~840. There is a madspin crash in

the very end of the log file, but that is unrelated to what I describe here.

[3] Cards at https:/

The "customizecards

respect to the model defaults.

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