restart nastran

•MSC.Software Technical Session

Restarts!

Save The Bytes!

“Green” Analysis with MSC Nastran

Getting the most out of your compute cycles &

your database filesPrafulla Kulkarni/ MSC Software Aug 2011

MSC.Software Technical Session

Today’s Agenda

•2

• Introduction to restarts

• Structure of the MSC.Nastran input file

• User Interface for a restart.

• Restart in Static analysis

• Restart in Dynamic analysis

• Restart in Non-linear analysis


Re-using what’s already been run

• What is a restart?

• Why would I use one?

• When would I use one?

• When wouldn’t I use one?

• How do I use one?

• So what‟s the catch?

•3


What is a restart?

• Restarts are fairly intelligent

– Make use of data stored in MASTER/DBALL files

– Evaluates what has changed in the input deck

– Removes any existing matrices/tables that would

be affected by those changes (if any)

– Retains any that are not

– Re-calculates only what is necessary

– No user directions required

•4

MASTER/

DBALL

• A restart is an MSC Nastran run that makes use

of already-stored-in-the-database info (instead of

re-calculating the exact same set of data. Again.

And again…)


Why would I use one?

• Key Benefits:

– Model configuration control (better)

– Increased analysis/data recovery throughput (faster)

– Reduced license usage (cheaper)

•5

Cheaper

Better Faster


When would I use one?

• Typical FEA process1. Read in bulk data deck

2. Formulate global mass/stiffness matrices (grids & elems) [KGG], [MGG]

3. Apply boundary conditions (SPC set) [KFF] [KAA]

4. Solve (“invert” – statics, eigenvalue – buckling & modes ….)

5. Apply loads {UL} = [KLL]-1 × {PL}

6. Calculate global displacements {UG} {UL}

7. Calculate stresses & strains based on displacements σ = [G]×{UG}

• Of these steps, #4 is the most costly (wall-clock time, CPU

resources, & license checkout duration)

– Anywhere ~after #4 makes sense (non-SE run)

– Almost anytime if only a few SE are changing

•6


When would I use one?

• Restarting makes sense when there is something to restart

from (#4 & beyond):

• Applicable Scenarios

– Need more results output

– New loads to run

– Modes done, modal transient / frequency response next

– Change NLPARM for last 15% of the load

– Changes to just a few SE

•7

SuperElements

Nonlinear

Modal Response

Just Loads

Data Recovery


When wouldn’t I use restarts?

• Changes that affect (any) element stiffness/mass

– Thickness, bar area, grid point location, …

• Boundary Condition change (different SPCs or MPCs)

– BCs are applied near the beginning before the “solve”

– Note: Any new “SPC=“ or “MPC=“ callout is a new BC

• Regardless whether any new DOFs are constrained or not

– Changes to the “METHOD=“ or EIGR/EIGRL entries

• Again, any changes will trigger a new eigenvalue solve

• Approach changes (non-SE)

– Statics Modes

– Modal Transient Direct Transient

•8

MASTER/

DBALL

http://www.nofenders.net/uploaded_images/Red-Flag-746633.jpg


How do I use one?

• Basic Instructions:

A. Do not delete the database after a run

B. Reference the database in the next run

C. Tell the program you are doing a restart

•9


MSC Nastran Database Organization

• The MSC Nastran “database system” has three (3) principal

database components:

1. The Brains (MASTER)

• Knows where everything is stored (index)

2. The Bulk (DBALL)

• Where all the 1s and 0s are stored

3. The Fleeting (SCRATCH)

• Data that typically would NOT be used for restarting

•10


How do I use one?

• Initial (coldstart) run:

– Save the database (MASTER/DBALL files)

• Use “scr=no” keyword

• Restart run:

– FMS:

• Reference existing database via ASSIGN statement

• Add RESTART command

•11

MASTER/

DBALL

Coldstart runASSIGN MASTER='Ex_01.MASTER', DELETE $ Remove old

ASSIGN DBALL='Ex_01.DBALL', DELETE $ databases

:

Restart RunASSIGN MASTER='Ex_01.MASTER', OLD $ Insure old

ASSIGN DBALL='Ex_01.DBALL', OLD $ (OPTIONAL)

RESTART $ Required!!!

:


How do I use one?

• Restart run - Exec & Case Control

– Program keys off difference between coldstart & restart decks!

• Evaluate consequences of adding or removing commands

• Do NOT overthink or try to out-guess automatic restart logic

•12

• Load has changed

from “100” to <none>

• SPC set has changed

from “200” to <none>

– New BC means new

[KLL] to form & solve!

SOL 101

CEND

LOAD = 100

SPC = 200

BEGIN BULK

:

Coldstart

SOL 101

CEND

$ LOAD = 100

$ SPC = 200

BEGIN BULK

:

Restart


How do I use one?

• Restart run (cont‟d):

– Bulk Data Section:

• User specifies additions &/or subtractions (only)

– If the bulk data is unchanged, then NO bulk data deck is required for the

restart run!

• Add any new items

– New FORCEs, dynamic loadings, FREQi entries, TABLEDi…

• Remove items via the slash entry “/,n1,n2” to remove sorted bulk

data entries n1 through n2

– Common technique is to remove all lines ( /,1,99999) and then re-

include entire bulk data deck

– Convenient, not necessarily efficient

•13


How do I use one? – Example 1 – STATIC

Data Recovery case

• Data Recovery Restart Example

– Nothing “new” to solve

– Only difference is output request

– No Bulk Data required (!)

•14



$

$

SOL 101

CEND

TITLE=Restart Example 01 - COLDSTART RUN

LOAD = 100

DISP = ALL

$

$

$

BEGIN BULK

CELAS2, 10, 1.E5, 2000

SLOAD, 100, 2000, 535.

ENDDATA

Restart RunASSIGN MASTER='Ex_01.MASTER', OLD $ Insure old

ASSIGN DBALL='Ex_01.DBALL', OLD $ (OPTIONAL)

RESTART $ Required!!!

$

SOL 101

CEND

TITLE=Restart Example 01 - Data Recovery Restart

LOAD = 100 $ Load did not change so keep it

$ DISP = ALL $ This IS a change

$

FORCE=ALL $ New request

$

BEGIN BULK

$ Nothing changed in Bulk Data, so nothing

$ needs to be in bulk data

ENDDATA

Ex01_CS_00.dat

Ex01_RS_01.dat


Restart f06 output

RESTART EXAMPLE 01 - DATA RECOVERY RESTART MAY 5, 2010 MD NASTRAN 5/ 9/08 PAGE 4

S O R T E D B U L K D A T A E C H O

ENTRY

COUNT . 1 .. 2 .. 3 .. 4 .. 5 .. 6 .. 7 .. 8 .. 9 .. 10 .

1- CELAS2 10 1.E5 2000

2- SLOAD 100 2000 535.

ENDDATA

TOTAL COUNT= 3

M O D E L S U M M A R Y

NUMBER OF CELAS2 ELEMENTS = 1

________________________________________________________________________________________________________________________


________________________________________________________________________________________________________________________


F O R C E S I N S C A L A R S P R I N G S ( C E L A S 2 )

ELEMENT FORCE ELEMENT FORCE ELEMENT FORCE ELEMENT FORCE

ID. ID. ID. ID.

10 5.350000E+02

________________________________________________________________________________________________________________________


. . .

. . .

________________________________________________________________________________________________________________________

* * * END OF JOB * * *

•15


How do I use one? “Read-Only” Restart

• “Read-Only” Restart

– 2nd run has “read-only” access to original

database files

– Protects original database from inadvertent

overwrites

– Ideally suited for configuration control methods

– Allows multiple simultaneous user access to

original database

•16


How do I use one? – Example 2 – Read Only

– STATIC - Data Recovery case

• Data Recovery Read Only Restart Example

– Nothing “new” to solve

– Only difference is output request

– No Bulk Data required (!)

•17



$

$

SOL 101

CEND

TITLE=Restart Example 01 - COLDSTART RUN

LOAD = 100

DISP = ALL

$

$

$

BEGIN BULK

CELAS2, 10, 1.E5, 2000

SLOAD, 100, 2000, 535.

ENDDATA

Restart RunASSIGN STATIC ='Ex_01.MASTER', OLD $ Insure old

RESTART LOGICAL = STATIC $ Required!!!

$

SOL 101

CEND

TITLE=Restart Example 01 - Data Recovery Restart

LOAD = 100 $ Load did not change so keep it

$ DISP = ALL $ This IS a change

$

FORCE=ALL $ New request

$

BEGIN BULK

$ Nothing changed in Bulk Data, so nothing

$ needs to be in bulk data

ENDDATA


So what’s the catch?

• The “cost” of Better, Faster, Cheaper:– Upfront planning for MASTER/DBALLs

• “SCR=NO” is often the default setting

– Use of FMS commands• File Management Section

– Size dependency• If job only takes 3 minutes to run, why bother?

– Working with the Automatic Restart Logic• Intentionally analysis “conservative”

• Change to one datablock may trigger unintended re-compute

• Use DIAG 56 for very useful restart info in f04

•18

$$$


Automatic Restart Logic

• USE “DIAG 56” in Exec Section

– Provides detailed restart logic info to f04 file

– Changes noted at field-level (see BAR data recovery pts below)

– Tells you what has been deleted and why

•19

9:43:23 0:00 184.0 0.0 0.3 0.0 IFPL 362 RESTART BEGN

The following items have changed in data block EPT

Record :Entry :Item Record :Entry :Item Record :Entry :Item Record :Entry :Item

PBAR : :C1 PBAR : :C2 PBAR : :D1 PBAR : :D2

PBAR : :E1 PBAR : :E2 PBAR : :F1 PBAR : :F2

:

9:43:24 0:01 208.0 0.0 0.4 0.0 PHASE0 1409 RESTART BEGN

The following items have changed in data block GEOM3S

Record :Entry :Item Record :Entry :Item Record :Entry :Item Record :Entry :Item

FORCE : :SID FORCE : :G FORCE : :CID FORCE : :F

FORCE : :N

9:43:24 0:01 208.0 0.0 0.4 0.0 PHASE0 1409 RESTART END

9:43:24 0:01 208.0 0.0 0.4 0.0 PHASE0 1410 IF BEGN

9:43:24 0:01 208.0 0.0 0.4 0.0 PHASE0 1415 ENDIF BEGN

9:43:24 0:01 208.0 0.0 0.4 0.0 PHASE0 1416 RESTART BEGN

*56* The following items are deleted due to changes (Name : DB-Data Block or P-Parameter or VP-Virtual Parameter : Count):

PTELEM :DB: 1 PJGRV :DB: 1 PJ :DB: 1 PG :DB: 1 PGGRV :DB: 1 PSS :DB: 1

UOO :DB: 1 EPSSEO :DB: 1 UOX :DB: 1 PA :DB: 1 PAGRV :DB: 1 PCHNG :P : 1

PL :DB: 1 QR :DB: 1 UL :DB: 1 CRX :DB: 1 EPSSEX :DB: 1 LOADGENX:P : 1

LOADREDX:P : 1 SESUM :DB: 1 EST :DB: 1 VGFD :DB: 1 FREQDEPS:P : 1 SLT :DB: 1

9:43:24 0:01 209.0 1.0 0.4 0.0 PHASE0 1416 RESTART END


Restart in Dynamic Analysis

• In dynamic analysis, the calculation of normal modes is, in general, the

most expensive operation.

• Therefore, a common application of restart is the performance of a

transient or frequency response analysis by restarting from the normal

modes calculation.


Restart in Dynamic Analysis - Example 3

• Modes Modal Response as Read-Only Restart

•21

Coldstart runASSIGN MASTER='modes.MASTER', delete $

ASSIGN DBALL='modes.DBALL', delete $

$

$

$

SOL 103 $ Normal Modes

CEND

$

TITLE = Restart Ex 2 - Coldstart run/modes

$

DISPL(PLOT)=ALL

$

$

METHOD = 10301

$

$

$

$

$

$

BEGIN BULK

Restart RunINIT MASTER(S) $ SCRATCH run!

ASSIGN MODES='modes.MASTER', old $ Reference

$ $

RESTART LOGICAL=MODES $ Note

$

SOL 111 $ Modal Frequency Response

CEND

$

TITLE = Restart Ex 2 - Modal Freq Response

$

DISPL(PLOT)=ALL

ACCEL(PLOT)=ALL

$

METHOD = 10301 $ Do NOT change this!

$

SDAMP = 11101

DLOAD = 11102

FREQ = 11103

OUTPUT(XYPLOT) $

XYPUNCH ACCE /111(T3RM), 211(T3RM)

BEGIN BULK

Ex03_CS_00.dat

Ex03_RS_01.dat



• SOL111 Random Read-Only Restart

•22

Coldstart run$ ......................run1.dat.................

INIT MASTER(S)

SOL 111 $ Modal Frequency Response

CEND

spc = 77

acceleration(phase,plot) = all

METHOD = 219

SDAMP = 11102

FREQ = 604

SUBCASE 11101 $ Modal Frequency Response

DLOAD = 11103

BEGIN BULK

param,wtmass,.00259

conm2,999,99,,1.e8

suport,99,123

Coldstart runspc1,77,456,99

$ Harmonic Load, Output Frequencies, and Damping PARAMs

eigrl,219,-.1,200.

TABDMP1 11102 CRIT

0. .06 99999. 0.6 ENDT

RLOAD1 11103 11105 11106

DAREA,11105,99,3,1.e8

TABLED1 11106

0. 0. 10. 1. 2000. 1. 3000. 0.

99999. 0. ENDT

$

Freq4,604,10.,200.,.1,5

freq1,604,50.,50.,30

$ Followed by Grid and Element data…

ENDDATA

Ex04_run1.dat

Ex04_run2.dat



• SOL111 Random Read-Only Restart

•23

Restart runinit master(s)

restart logical=run2

Assign run2='run1.MASTER'

$ run2.dat

SOL 111 $ Modal Frequency Response + Random

Input

CEND

$

spc = 77

METHOD = 219

SDAMP = 11102

FREQ = 604

RANDOM = 11107

SUBCASE 11101 $ Modal Frequency Response

DLOAD = 11103

Restart run$

output(xyplot)

xyprint accel psdf / 104(t3)

xyprint accel psdf / 105(t3)

BEGIN BULK

$

$

RANDPS 11107 11101 11101 1. 0. 11108

$

TABRND1 11108

0.0 0.2 2000. 0.2 endt

$

ENDDATA

Ex04_run1.dat

Ex04_run2.dat



• SOL103 SOL112 Read-Only Restart

•24

Coldstart run----------modes.dat-------------------------

SOL 103

CEND

$

DISP(PLOT)=ALL

ESE(PLOT)=ALL

SPC = 777 $ for fixed base

METHOD = 100

$

BEGIN BULK

PARAM,POST,0

EIGRL, 100, ,400.0

SPC1, 777, 123456, 1, 2

Coldstart run$ Large masses that are used in the enforced motion

CONM2, 1017, 17, , 1.0E6

CONM2, 1071, 71, , 1.0E6

$

$ Followed by Grid and Element data…

ENDDATA

Ex05_run1.dat

Ex05_run2.dat



• SOL103 SOL112 Read-Only Restart

•25

Restart runASSIGN MODE='modes.MASTER'

RESTART, logical=MODE

$

SOL 112

CEND

SET 33 = 5, 44, 69

DISP(PRINT)=33

$

METHOD = 100

SPC = 777 $ for fixed base

TSTEP = 200

DLOAD = 300

$

OUTPUT(XYPLOT)

Restart runXYPUNCH ACCEL/5(T3)

XYPUNCH ACCEL/95(T3)

BEGIN BULK

DAREA, 10, 17, 3, 1.0E6

DAREA, 20, 71, 3, 1.0E6

$

DLOAD, 300, 1.0, 1.0, 100, 1.0, 200

$ DAREA Type Freq Phase

TLOAD2, 100, 10, ,3 , ,1.0, 10.0

TLOAD2, 200, 20, ,3 , ,1.0, 30.0, 90.0

$

TSTEP, 200, 100, .001

$

ENDDATA

Ex05_run1.dat

Ex05_run2.dat


Restart in Nonlinear Static Analysis

• Performing a „read-only‟ restart for non-linear statics is used for

– Planned‟ segmentation of a large job

– Can be used for restarting failed jobs from the last saved loopid



• Run the first job with a percentage of the loading in SUBCASE 1 (say,

25%). Name the job accordingly. Be sure to save the databases. See

example file: plate-run1.dat.

Coldstart runSOL 106

CEND

$ data recovery requests

STRESS(PLOT,SORT1,REAL,VONMISES,BILIN)=ALL

NLSTRESS(PLOT)=ALL

$ This constraint will apply to all subcases... so put

above

SPC = 2

SUBCASE 10

SUBTITLE=25% of load

NLPARM = 10

LOAD = 100

$

BEGIN BULK

PARAM POST 0

Coldstart runPARAM LGDISP 1

PARAM,NOCOMPS,-1

$

NLPARM 10 10

$ Loads for Load Case : Default

LOAD 100 1. .25 1

$ Displacement Constraints of Load Set : spc-a

SPCADD 2 1

SPC1 1 123456 1 2 3

$ Nodal Forces of Load Set : force-a

FORCE 1 61 0 10000. 0. 0. -1.

FORCE 1 62 0 10000. 0. 0. -1.

FORCE 1 63 0 10000. 0. 0. -1.

$ Followed by Grid and Element data.



• Any converged and saved solution always gives the messages in your f06

file

*** USER INFORMATION MESSAGE 6186 (NCONVG)

*** SOLUTION HAS CONVERGED ***

SUBID 1 LOOPID 13 LOAD STEP 1.000 LOAD FACTOR 1.00000000

^^^ USER INFORMATION MESSAGE 9005 (NLSTATIC)

^^^ THE SOLUTION FOR LOOPID= 13 IS SAVED FOR RESTART

^^^

^^^ USER INFORMATION MESSAGE 9052 (NLSTATIC)

^^^ NONLINEAR STATIC ANALYSIS COMPLETED.

^^^

1 SAMPLE NONLINEAR READ-ONLY RSTART SERIES... RUN1, THE COLD START JULY 31, 2008 MSC.NASTRAN 4/ 3/07 PAGE 46

0

1 SAMPLE NONLINEAR READ-ONLY RSTART SERIES... RUN1, THE COLD START JULY 31, 2008 MSC.NASTRAN 4/ 3/07 PAGE 47



• Any restart in SOL 106 must have the FMS command RESTART and the

two parameters PARAM,SUBID,value and PARAM,LOOPID,value

• The SUBID is the sequential number of a subcase. It is recommended

that the SUBID value always be incremented by one and point to a new

subcase.

• The LOOPID is the identifier of the converged solution from which the

restart is to take place.



• To do restart job from previous job

– Establish it as a „read-only‟ restart by adding the following lines to the

FMS…

• ASSIGN RUN1=‟plate-run1.MASTER‟

• RESTART VERSION=LAST LOGICAL=RUN1

– Add PARAM,LOOPID,13 (where 13 is the last saved increment

identified in the .f06 file of run1)

– Add PARAM,SUBID,02 (where 02 is the #of subcases in run1 +1) to

the case control above the first subcase.

– Remove the entire bulk data section.

– Add the new subcase with callouts to loading, nlparm cards (only add

the necessary cards to the bulkdata section if they are different than

those used in run1).

• Repeat as many times as desired.



Restart Run$ assign the database to restart off...

assign run1='plate-run1.MASTER'

restart version=last logical=run1

$

SOL 106

TIME 600

CEND

TITLE = sample nonlinear read-only rstart series... run2, first

restart

ECHO = sorted

$ data recovery requests

STRESS(PLOT,SORT1,REAL,VONMISES,BILIN)=ALL

NLSTRESS(PLOT)=ALL

$ This constraint will apply to all subcases... so put above

SPC = 2

$ define which loopid from the .f06 file to restart from

$ and which subcase to restart into... in this case the second

PARAM,LOOPID,13

PARAM,SUBID,2

Restart Run$ first subcase with a percentage of the loading (controlled by

scale factor on load card)

SUBCASE 10


NLPARM = 10

LOAD = 100

$ add new subcase with a callout for a new load and nlparm

card

SUBCASE 20


NLPARM = 20

LOAD = 200

BEGIN BULK

$ only NEW information is in the bulkdata... everything else is

removed.

NLPARM 20 5

$ new load card with scale factor of .5 applied to the same

forces as in run1

LOAD 200 1. .50 1

ENDDATA


Restart in Nonlinear Transient Analysis

• Restarts are controlled by parameters LOOPID, STIME

• The normal restart for a transient run is to be continued from the last step

of a previous subcase with different loads and/or TSTEPNL data.

• For the normal restart provide the following parameters:

LOOPID = N : Start from the Nth subcase

STIME = t : Start from time t

• input value for STIME differs depending on the value of METHOD

specified on the TSTEPNL entry.


Restart in Nonlinear Transient Analysis

Coldstart Run------------a129.dat-------------------------

SOL 129 $ NonLinear Transient Response

CEND

DISPL=ALL

STRESS=ALL

SUBCASE 12901 $ Nonlinear Transient Response

LoadSet = 199

DLOAD = 12901

TSTEPNL = 12902

BEGIN BULK

TLOAD1 12901 12903 0 12904

TSTEPNL 12902 5 .01 1

lseq,199,12903,99

PARAM,LGDISP,+1

PARAM W3 1000.

PARAM G .08

$followed by load , element and node data

ENDDATA

Restart Runassign run3 ='a129.MASTER'

restart logical=run3

SOL 129 $ NonLinear Transient Response

CEND

DISPL=ALL

STRESS=ALL

param,loopid,1

param,stime,0.05


LoadSet = 199

DLOAD = 12901

TSTEPNL = 12902


TSTEPNL = 12903

BEGIN BULK

TSTEPNL 12903 5 .01 1

ENDDATA


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•34

Hot Line Support

http://support.mscsoftware.com/servicerequest/

Visit SimCompanion to find answers fast and leverage all technical support resources.

http://simcompanion.mscsoftware.com

Attend a training course to help improve productivity.

http://www.mscsoftware.com/training

Leverage engineering services to accelerate the benefits of virtual product development with

confidence.

http://www.mscsoftware.com/services

For Additional information on Restart – Refer

•Nastran Linear Static Guide

•Nastran Reference Manual

•Basic Dynamic user’s Guide

http://support.mscsoftware.com/servicerequest/

http://simcompanion.mscsoftware.com/

http://www.mscsoftware.com/training

http://www.mscsoftware.com/services


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•35

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