[Bug]: re-enable use of do_forecast = 0

[iantaylor-NOAA]

Describe the bug

The attached model is modified from the "simple_small" model included in the r4ss package:
simple_small_forecast_bug.zip

The only changes are turning off the benchmarks and forecast via these lines in the forecast file:

0 # Benchmarks: 0=skip; 1=calc F_spr,F_Btgt,F_msy; 2=calc F_spr,F0.1,F_msy; 3=add F_Blimit; 
...
0 # Forecast: -1=none; 0=simple_1yr; 1=F(SPR); 2=F(MSY) 3=F(Btgt) or F0.1; 4=Ave F (uses first-last relF yrs); 5=input annual F scalar

When run with 3.30.24.2 or the pre-release of 3.30.25, it produces an error after estimation. This error did not occur with 3.30.21 (requires removing a line from the starter file to run):

>ss3 -nohess -stopph 0
 reading from starter.ss
 reading from data file
Data read successful 999

 reading forecast file
 reading from control file
End of control file successful! 999
Begin setting up parameters ...  end of parameter section
Evaluating biology calculations once ... done

 - final statistics:
1 variables; iteration 0; function evaluation 0
Function value   7.7039e+02; maximum gradient component mag  -3.1391e-14
Exit code = 0;  converg criter   1.0000e+01
Var   Value    Gradient   |Var   Value    Gradient   |Var   Value    Gradient
  1 -0.00000  -3.1391e-14 |
Iterations: 2
array bound exceeded -- index too high in prevariable::operator()

To Reproduce

Steps noted above

Expected behavior

Run without array error

Screenshots

No response

Which OS are you seeing the problem on?

No response

Which version of SS3 are you seeing the problem on?

No response

Additional Context

I've looked through the SS_readdata_330.tpl to see if I can find the error but didn't come up with anything. I asked for help from github copilot and it suggested changing this line: 2b19df5 but after creating a branch and pushing that change, I realized that it didn't actually fix the problem. Copilot failed to come up with anything else to fix.

@Rick-Methot-NOAA, my next move would be to more systematically go through the code to isolate where the problem occurs, but do you have an idea for where to look first?

[Rick-Methot-NOAA]

runs fine with this change:
-1 # Forecast: -1=none; 0=simple_1yr; 1=F(SPR); 2=F(MSY) 3=F(Btgt) or F0.1; 4=Ave F (uses first-last relF yrs); 5=input annual F scalar

[iantaylor-NOAA]

Good catch. So it's the 1-year forecast that's added somehow interacting poorly with no benchmarks. We could just add a message saying that the "simple_1yr" forecast option isn't available without benchmarks.

[Rick-Methot-NOAA]

I misunderstood what you wanted. I will make a SS3 change such that simple 1yr forecast works with no benchmark.

[iantaylor-NOAA]

Sorry, I was sloppy in my use of "turning off forecast". The SSMSE code that was failing likely could be changed to use forecast = -1 instead of forecast =0, but it's still beneficial to either have a clear error message or enable the model to play through without error in case someone else runs across the same problem by accident.