Hi here,

I am using ccx to solve biomechanic problems.

Currently we have generated INP files with different sized geometries and doing static FE analysis.

This results in element counts between ~100.000 to 400.000 (quadratic tet)

We use PASTIX as a standard solver and most models run smoothly. But larger break up strangely.

The models which break up have element counts **greater than 250.000 elements.** Smaller models run smoothly. All have the same boundary conditions and contact formulations.

So I suggest, that there has to be a problem with the number of elements?

Normally I start ccx from a python routine. Here it returns

*ccx_static.exe: returned non-zero exit status 3221225725*

( â†’ *Stack overflow / exhaustion.* Error can indicate a bug in the executed software that causes stack overflow, leading to abnormal termination of the software.)

If i start ccx directly in a PowerShell calculix and the solver start normally and then the solver just terminates, without any feedback or error (see code attached of one example)

**What I tested so far:**

Using SPOOLES, PASTIX, PARDISO and INTERATIVE CHOLESKY does not make a difference. All break up with no error at all.

Change the number of threads between 1 and 16 does not effect the breakup

Change between ccx 2.20. and ccx 2.21 did not affect anything

Starting ccx with â€ś-iâ€ť did not change anything

My test machine has 16 Cores, 128 GB RAM and enough space on a SSD on Windows

**Any search did not help me out of this problem. Does someone have an idea what could cause this breakup?**

Thanks and best regards from south Germany, Lucas

â€¦

CalculiX Version 2.21, Copyright(C) 1998-2023 Guido Dhondt

CalculiX comes with ABSOLUTELY NO WARRANTY. This is free

software, and you are welcome to redistribute it under

certain conditions, see gpl.htm

You are using an executable made on Sat Jul 29 17:18:34 2023

The numbers below are estimated upper bounds

number of:

nodes: 605775

elements: 373698

one-dimensional elements: 0

two-dimensional elements: 0

integration points per element: 4

degrees of freedom per node: 3

layers per element: 1distributed facial loads: 0

distributed volumetric loads: 0

concentrated loads: 947

single point constraints: 4050

multiple point constraints: 1

terms in all multiple point constraints: 1

tie constraints: 53

dependent nodes tied by cyclic constraints: 0

dependent nodes in pre-tension constraints: 0sets: 134

terms in all sets: 1661060materials: 2

constants per material and temperature: 8

temperature points per material: 1

plastic data points per material: 0orientations: 0

amplitudes: 2

data points in all amplitudes: 2

print requests: 0

transformations: 0

property cards: 0

Decascading the MPCâ€™sDetermining the structure of the matrix:

Using up to 8 cpu(s) for setting up the structure of the matrix.

number of equations

1666587

number of nonzero lower triangular matrix elements

83208279increment 1 attempt 1

increment size= 1.000000e-02

sum of previous increments=0.000000e+00

actual step time=1.000000e-02

actual total time=1.000000e-02iteration 1

Number of contact spring elements=570693

Determining the structure of the matrix:

maximal possible contact elements =

570693Using up to 8 cpu(s) for setting up the structure of the matrix.

number of equations

1666587

number of nonzero lower triangular matrix elements

84612387Using up to 8 cpu(s) for the stress calculation.

Using up to 8 cpu(s) for the symmetric stiffness/mass contributions.

Not reusing csc.

Â±------------------------------------------------+

`PaStiX : Parallel Sparse matriX package +`

Â±------------------------------------------------+

Version: 6.0.1

Schedulers:

sequential: Enabled

thread static: Started

thread dynamic: Disabled

PaRSEC: Disabled

StarPU: Disabled

Number of MPI processes: 1

Number of threads per process: 8

Number of GPUs: 0

MPI communication support: Disabled

Distribution level: 2D( 128)

Blocking size (min/max): 1024 / 2048Matrix type: General

Arithmetic: Float

Format: CSC

N: 1666587

nnz: 170891361Â±------------------------------------------------+

Ordering step :

Ordering method is: Scotch

Time to compute ordering: 2.8737

Â±------------------------------------------------+

Symbolic factorization step:

Symbol factorization using: Fax Direct

Number of nonzeroes in L structure: -1298756719

Fill-in of L: -7.599897

Time to compute symbol matrix: 0.6063

Â±------------------------------------------------+

Reordering step:

Split level: 0

Stoping criteria: -1

Time for reordering: 3.7589

Â±------------------------------------------------+

Analyse step:

Number of non-zeroes in blocked L: 1697453858

Fill-in: 9.932941

Number of operations in full-rank LU : 39.42 TFlops

Prediction:

Model: AMD 6180 MKL

Time to factorize: 712.6018

Time for analyze: 0.0812

Â±------------------------------------------------+

Factorization step:

Factorization used: LU

Time to initialize internal csc: 2.7088