TELEMAC-MASCARET Forum: Floating Point Errors

Welcome, Guest

TOPIC: Floating Point Errors - calcot

Floating Point Errors - calcot 4 years 8 months ago #37071

olslewfoot

Hi all
I'm running a telemac3D model in v8p1r0 and have a stop error in Calcot from some very small Floating Point value differences.

================================================================================
ITERATION 0 TIME 0 D 0 H 0 MN 0.0000 S ( 0.0000 S)
================================================================================

MASS BALANCE
INITIAL MASS OF WATER IN THE DOMAIN : 617939192858875.75
TELEMAC3D COUPLED WITH: NOTHING
CALCOT: PLANES 5 AND 6
INTERCROSS AT POINT 2
LOWER POINT : -3767.8034667968750
HIGHER POINT: -3767.8034667968755
DIFFERENCE : -4.5474735088646412E-013Note: The following floating-point exceptions are signalling: IEEE_OVERFLOW_FLAG IEEE_UNDERFLOW_FLAG IEEE_DENORMAL

DEPTH : -9.0949470177292824E-013
STOP 1
PLANTE: PROGRAM STOPPED AFTER AN ERROR

How can these be overcome? They're not real errors I think.

Best Regards
John

The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37073

pham OFFLINE Administrator Posts: 1622 Thank you received: 621	Hello John, This may happen if you have tidal flats. Have you set TIDAL FLATS = YES or let the default value (= YES)? Do you have big velocities at that location? Maybe you can share you steering file + FORTRAN files if you have some. Best regards, Chi-Tuan
	The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37074

olslewfoot

Hi Chi-Tuan

I'm not using Tidal Flats as the domain is microtidal and the shelf steep so I selected TIDAL FLATs= No. Velocities are quite low - but the model has not yet started, still at initiation.

I've attached the steering file and the modified fortran files.

Any suggestions gratefully received.

Attachments:

The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37075

pham OFFLINE Administrator Posts: 1622 Thank you received: 621	John, Even if you do not have tidal flats, I would first try to set TIDAL FLATS = YES. Chi-Tuan
	The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37077

olslewfoot	Chi-Tuan This worked. Using TIDAL FLATS overcomes the error. Thanks for the help. John
	The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37078

pham OFFLINE Administrator Posts: 1622 Thank you received: 621	Good news John, thanks for the feed back: Chi-Tuan
	The administrator has disabled public write access. The following user(s) said Thank You: olslewfoot

Floating Point Errors - calcot 4 years 8 months ago #37081

olslewfoot	Chi-Tuan I have one more question? Telemac used to call PLANTE if limits were exceeded (v6p1 and before?). There are times at present when I am running a model and it continues although there are NaN values posted in the Listing? Should this not trigger PLANTE, I suppose it depends on each function. John
	The administrator has disabled public write access.

Floating Point Errors - calcot 4 years 8 months ago #37083

pham OFFLINE Administrator Posts: 1622 Thank you received: 621	John, You have a clean stop with PLANTE in a subroutine only if an error or a stop was planned by the developer. If not and you get NaN, you should try a debug configuration to try to track the bug. See which debug options are used in e.g. systel.edf.cfg Hope this helps, Chi-Tuan
	The administrator has disabled public write access. The following user(s) said Thank You: olslewfoot