# interface to external program / command line and optimisation \[beginner\] **URL:** \ **Category:** Questions\ **Tags:** engineering, mathematica, external-interfaces, optimization\ **Created:** [August 9, 2015, 6:06pm UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390 "2015-08-09T18:06:49Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![geotrupes](https://avatars.discourse-cdn.com/v4/letter/g/439d5e/32.png) [@geotrupes](https://community.wolfram.com/u/geotrupes)\ **Post date:** [August 9, 2015, 6:06pm UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/1 "2015-08-09T18:06:49Z")
Trying to: -1- define a function which takes a number [step 1], write to a file [step 2], runs an external bash script [step 3], read a text file and return the result as a number [step 4] -2- trying to optimise this function with NMinimize Here is the code of the function: ``` f[x_] := CompoundExpression[SetDirectory["~/Desktop/test"]; Print[x]; (*this is for debugging*) Export["in.data", N[x], "Text"]; (*this saves the value x in a text file*) Run["~/Desktop/test/run.sh"]; (*this runs a shell script which \ takes the text file, read it and makes the square of the number in in, a place holder for more to come*) N[ToExpression[ Import["out.data"]]](*this reads the number from the script \ output and convert to number*) ] ``` If I use: f[10], all if fine. the result is 100. However if I use: ``` NMinimize[{f[y], 0 < y < 10}, {y}, Method -> "SimulatedAnnealing"] ``` The results is nonsense as the function writes “y” in the first text file as symbolic form. Any idea on how to make this work? Thanks G. ---
**Author:** ![bsimpson141421356](https://avatars.discourse-cdn.com/v4/letter/b/ac91a4/32.png) [@bsimpson141421356](https://community.wolfram.com/u/bsimpson141421356)\ **Post date:** [August 9, 2015, 6:22pm UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/2 "2015-08-09T18:22:28Z")
Perhaps [this](http://support.wolfram.com/kb/12502) ---
**Author:** ![geotrupes](https://avatars.discourse-cdn.com/v4/letter/g/439d5e/32.png) [@geotrupes](https://community.wolfram.com/u/geotrupes)\ **Post date:** [August 9, 2015, 6:39pm UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/3 "2015-08-09T18:39:01Z")
Thank you Bill, tried and it works ``` f[x_?NumericQ] := CompoundExpression[ SetDirectory["~/Desktop/test"]; Print[N[x]]; Export["in.data", N[x], "Text"]; Run["~/Desktop/test/run.sh"]; result = N[ToExpression[Import["out.data"]]] ; Run["rm *.data"]; Print[result] ``` There are few issues to resolve but this is great. THANK YOU! G. PS do you happen to know if this is running in a multicore fashion? ---
**Author:** ![geotrupes](https://avatars.discourse-cdn.com/v4/letter/g/439d5e/32.png) [@geotrupes](https://community.wolfram.com/u/geotrupes)\ **Post date:** [August 9, 2015, 8:49pm UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/4 "2015-08-09T20:49:31Z")
I seem to be stuck. When I evaluate the function on its own all is fine. Even when the optimisation starts, but gets stack after 2 cycles. It looks like there is a multicore batch happening, therefore the output is messed up. I tried switching off cores and nothing happens. I also tried to change the code so an index keeps each run separate, but at no avail. here is the modified text: ``` f[x_?NumericQ] := CompoundExpression[ SetDirectory["~/Desktop/test"]; index = ToExpression[Import["index.ini"]]; (* *)Print[index];(* Print[N[x]]; *) indexname = ToString[index]; Export["in." <> indexname <> ".data", N[x], "Text"]; Run["~/Desktop/test/run.sh " <> indexname]; result = N[ToExpression[Import["out." <> indexname <> ".data"]]]; Run["rm *.data"]; index = index + 1; Print[index]; Export["index.ini", indexname, "Text"]; Print[result]; ] ``` and here is the crash. ``` NMinimize[{f[y], 0 < y < 10}, {y}, Method -> "SimulatedAnnealing"] 0 1 0.20914 0 1 0.20914 NMinimize::nnum: The function value Null is not a number at {y} = {0.457318}. >> 0 1 0.20914 0 1 0.20914 NMinimize::nnum: The function value Null is not a number at {y} = {0.457318}. >> 0 1 0.20914 0 1 0.20914 NMinimize::nnum: The function value Null is not a number at {y} = {0.457318}. >> General::stop: Further output of NMinimize::nnum will be suppressed during this calculation. >> 0 1 0.20914 0 1 0.20914 NMinimize[{f[y], 0 < y < 10}, {y}, Method -> "SimulatedAnnealing"] ``` any idea? Thanks G. ---
**Author:** ![geotrupes](https://avatars.discourse-cdn.com/v4/letter/g/439d5e/32.png) [@geotrupes](https://community.wolfram.com/u/geotrupes)\ **Post date:** [August 10, 2015, 12:07am UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/5 "2015-08-10T00:07:56Z")
Ok, I tried a simpler function. Using echo to print a square, made in Mathematica. See this: ``` f[x_?NumericQ] := RunProcess[{"echo", ToString[InputForm[x^2, NumberMarks -> False]]}, "StandardOutput"]; ``` It works for a single value of x, but then NMinimize complains that: ``` NMinimize[{f[y], 1 < y < 10}, {y}, Method -> "RandomSearch"] NMinimize::nnum: The function value 1.9925755057065486` is not a number at {y} = {1.41159}. >> ``` What is the issue? I must confess to be rather lost at this stage ☹ Thanks G\> ---
**Author:** ![bsimpson141421356](https://avatars.discourse-cdn.com/v4/letter/b/ac91a4/32.png) [@bsimpson141421356](https://community.wolfram.com/u/bsimpson141421356)\ **Post date:** [August 10, 2015, 5:33am UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/6 "2015-08-10T05:33:32Z")
You think you are seeing this behaving as you expect ``` In[1]:= f[x_?NumericQ] := RunProcess[{"echo", ToString[InputForm[x^2, NumberMarks->False]]},"StandardOutput"]; f[3] ``` but if you then do this ``` Print[FullForm[%]] ``` I believe you will understand that your function is returning a string, not a numeric value, and trying to “minimize a string” isn’t going to work. If you are running Windows then ``` f[x_?NumericQ] := ToExpression[StringDrop[RunProcess[{"echo", ToString[InputForm[x^2, NumberMarks->False]]}, "StandardOutput"], -2]]; Print[FullForm[f[3]]] ``` might be closer to what you want. And if you aren’t running Windows then the StringDrop may need to be adjusted to match your local conventions. I think there should be a much better way of doing what you are trying to do. ---
**Author:** ![geotrupes](https://avatars.discourse-cdn.com/v4/letter/g/439d5e/32.png) [@geotrupes](https://community.wolfram.com/u/geotrupes)\ **Post date:** [August 10, 2015, 7:49am UTC](https://community.wolfram.com/t/interface-to-external-program-command-line-and-optimisation-beginner/6390/7 "2015-08-10T07:49:06Z")
The ToExpression solves the issue and all works!! I am very new to Mathematica an trying to run without knowing how to walk 🙂 If there is a better way and you have some idea please shoot! Thank you, G\>