Now over 1200 lines and I loaded initial values from the Dynamo example card deck. I ran my first time 'DT' cycle to step Dynamo model equations forward one time increment.

Dynamo is the simulator that ran the original Limits to Growth model.  A new page will be added to this website when the Limits to Growth model simulator is ready for prime time.  Users will be able to run the card deck and see the original graphs.  They will also be able to run their own versions.

The input card deck.

*    M478-248,DYN,TEST,1,1,0,0
RUN  2698JP
NOTE  MODEL OF RETAIL STORE
NOTE 
1L    IAR.K=IAR.J+(DT)(SRR.JK-SSR.JK)          INVENTORY ACTUAL
1L    UOR.K=UOR.J+(DT)(RRR.JK-SSR.JK)          UNFILLED ORDERS
20A  NIR.K=IAR.K/DT                          NEGATIVE INVENTORY
20A  STR.K=UOR.K/DFR                          SHIPMENTS TRIED
54R  SSR.KL=MIN(STR.K,NIR.K)                  SHIPMENTS SENT
40R  PSR.KL=RRR.JK+(1/DIR)(IDR.K-IAR.K)      PURCHASE ORDERS SENT
12A  IDR.K=(AIR)(RSR.K)                      INVENTORY DESIRED
3L    RSR.K=RSR.J+(DT)(1/DRR)(RRR              REQUISITIONS SMOOTHED
X1    .JK-RSR.J)
39R  SRR.KL=DELAY3(PSR.JK,DTR)                SHIPMENTS RECEIVED
NOTE 
NOTE  INITIAL CONDITIONS
NOTE 
12N  UOR=(DFR)(RRR)                         
6N    RSR=RRR                                 
6N    IAR=IDR                                 
NOTE 
NOTE  INPUT
NOTE 
7R    RRR.KL=RRI+RCR.K                        REQUISITIONS RECEIVED
45A  RCR.K=STEP(STH,5)                        REQUISITION CHANGE
NOTE 
NOTE  CONSTANTS
NOTE 
C    AIR = 8 WKS                              CONSTANT FOR INVENTORY
C    DFR = 1 WK                              DELAY IN FILLING ORDERS
C    DIR = 4 WKS                              DLY REFILLING INVENTORY
C    DRR = 8 WKS                              REQUISITION SMTHNG T C
C    DTR = 2 WKS                              DELAY IN TRANSIT
C    RRI = 1000 ITEMS/WK                      REQ. RECEIVED INITIALLY
C    STH = 100 ITEMS/WK                      STEP HEIGHT
NOTE 
PRINT 1)IAR,IDR/2)UOR/3)RRR,SSR/4)PSR,SRR
PLOT  IAR=I,UOR=U/RRR=R,SSR=S,PSR=P,SSR=Q
SPEC  DT=0.1/LENGTH=10/PRTPER=5/PLTPER=0

Results from reading and processing the input card deck.  The variables *001, *002, *003 are internally generated by expanding a delay card.  Getting this far took quite a bit of processing.  The hard work is done.  Now the devil will be in the details.

RSR	J	1000	K	1000
UOR	J	1000	K	1000
IAR	J	8000	K	8000
RCR	J	0	K	100
STR	J	1000	K	1000
IDR	J	8000	K	8000
NIR	J	80000	K	80000
RRR	JK	1000	KL	1100
SSR	JK	1000	KL	1000
PSR	JK	1000	KL	1000
SRR	JK	1000	KL	1000
*001	JK	1000	KL	1000
*002	JK	1000	KL	1000

   

DT	0.1
AIR	8
DFR	1
DIR	4
DRR	8
DTR	2
RRI	100
STH	100
*003	6.666666666666666

This output shows Dynamo sample model array variables.  The variables on the bottom are constants that do not change.  The variables above them have J and JK values.  J values are initial values.  The K and KL variables are the result of calculating to the next time increment.  The next step will be to  transfer K values to J values and KL values to JK values to step time again.

The Limits to Growth model has about ten time as many equation lines.  When it works and is ready for prime time, the equation simulator won't care about more lines.  First I have errors to fix.  The output is not correct^*.

This is what defines what I am doing.  The users manual.

Dynamo

Q: How will the JavaScript implementation compare in speed to the original IBM mainframe implementation?  A: The modern Javascript implementation will run rings around the original IBM implementation.

^* The errors were fixed.  But the output above is not corrected.  Output should have no values changing before a step input generates an order in the system at time five.