I'm having a bit of a problem modelling an optimization problem in matlab using a recursive algorithm (which is a requirement).

The problem is as such:

Decide the quantity of fish to catch each year considering a time window of 10 years knowing there are presently 10000 fishes in the lake, year 1, the growing rate of fish is the number of fishes present in the lake at the beginning of each year + 20%.

Let x be the quantity of fish to catch, $5 the price of each fish and the cost of catching fish:

0.4x + 100 if x is <= 5000; 0.3x + 5000 if 5000 <= x <= 10000; 0.2x + 10000 if x > 10000;

decide the number of fish to catch each year, for 10 years, in order to maximize the profit.

Future gains are depreciated by a factor of 0.2/year, which means that earning $1 in year 1 is the same as $0.8 in year 2 and so on.

I currently have defined the following objective function:

x -> quantity of fish to catch b-> quantity of fish availavable in the beginning of year i c(x,b) -> cost of catching x fish with b fishes available f_i(b) = max {(5x - c(x,b)) + 0.8 * f_i+1((b - x) * 1.2)}

This only computes fot the case where the year is 10 and b = 10 (value in thousands).
This is the same poblem describes as "Discounted Profits Problem" in book

EDIT: Can it be done in Java? Then it would be simpler to translate to matlab.

EDIT2: Code edited. Now i'm getting "Maximum recursion limit of 500 reached.". Heeelp

If you change the .pt in the link to .com, then it displays the book in English (at least for me).

Look at the top of page 59. There is your recursive function, right there. See how the function f(t,b) is based on f(t+1,floor(s(b-xt)))? So the function f calls itself. Recursion.

0

There are many ways to learn to code these days. From coding bootcamps like Flatiron School to online courses to totally free beginner resources. The best way to learn to code depends on many factors, but the most important one is you. See what course is best for you.

@TommySzalapski Can you show me a code example? I can't seem to grasp the concept. Evem more i don't know what the stop cndition would be. I keep getting errors with 0 indexing in matlab :(

@TommySzalapski Great. Can you take a look at my implementation?

I'm getting an "Attempted to access prop(2,0); index must be a positive integer or logical." error on line 66 of my Main file.

My implementation is:

Main file

clear; global M Kdep Cost RecursiveProfit ValorF prop Kdep=[10; 20; 30; 40; 50; 60; 70; 80; 90; 100]; %max nr of fish in the lake at the beginning of each year, 10 years, in thousands. Growth factor = 20% M=1000; %Cost and Profit of selling i fishes given that there are j at the beginning of the year for i = 1:50 for j = 1:11 Cost(i,j) = 0.2 * i + 10; RecursiveProfit(i,j) = 5 * i - Cost(i, j); end end for i = 1:10 for j = 1:10 Cost(i,j) = 0.3 * i + 5; RecursiveProfit(i,j) = 5 * i - Cost(i, j); end end for i = 1:5 for j = 1:5 Cost(i,j) = 0.4 * i + 0.1; RecursiveProfit(i,j) = 5 * i - Cost(i, j); end end %prop = 1 : 10; ValorF = -M * ones(10, 50); %Border conditions for a = 1:5 ValorF(10, a) = 5 * a - (0.4 * a + 1); %On Year 10, if there are <= a thousand fishes in the lake ... prop(10, a) = a; end for b = 6:10 ValorF(10, b) = 5 * b - (0.3 * b + 5); %On Year 10, if there are 6 <= a <= 10 thousand fishes in the lake ... prop(10, b) = b; end for c = 10:41 ValorF(10, c) = 5 * c - (0.2 * c + 10); prop(10, c) = c; end MaxProfit = RecursiveProfitRecursivo(1, 10) k1 = prop(1,10) kant=k1; y = 6 - Cost(kant,10); for q=2:10 if(kant == 0) kant = kant + 1; end kq=prop(q,y) kant=kq; y = y - Cost(kant,q); end %for i

function y=RecursiveProfit(j,x) global M Kdep Cost Prof ValorF prop y=ValorF(j,x); if y~= -M return end %if auxMax=-M; decision=0; for k=1:Kdep(j) if Prof(k,j) <= x-k aux=Prof(k,j)+RecursiveProfit(j+1, (x - k)); if auxMax < aux auxMax=aux; decision=k; end %if aux else break end %if Cost end %for k ValorF(j,x)=auxMax; prop(j,x)=decision; y=auxMax;

@TommySzalapski y is supposed to be the money available minus the cost associated with a "decision" for the problem. I based my code on some code for a similar problem (resource alocation). I forgot to edit that line.
In the original problem that expression is:

Money to invest (6) minus where to invest, and compute that 3 times (3 decisions to be made). In my version there are 10 decisions. k is supposed to be "decision", k1 "decision 1" and kant "previous decision".

Thank you very much for your help. I don't have words to express my gratitude. I'm really stuck and i'm on a very tight deadline :(

Yes, the English here is fine. I was only referring to the link you provided, as a reference no doubt, and the result. The change from google.pt to google.com seems to work.

It seems you've made good progress on this. I'm still trying to wrap my head around your code. If the objective function is this:

Then I would read it this way: "Maximum profit over 10 years given b fishes at the beginning of the ith year ....." I'm unclear on this.
It seems to me that you want:
Maximum profit over 10 years given a catch size of x_i for the ith year in each of the 10 years.
I'm assuming that the catch each year is different because you said:

decide the number of fish to catch each year

instead of "decide the equal number of fish to catch per year each and every year". But, perhaps I made a bad interpretation of the objective. Which is it?

Hey fmarshal. Sorry for not responding. The solution itself is 1 number, MaxProfit. But part os the solution is deciding how many fishes to catch each year, prop.

Yes. I understand the overall objective. What I still don't understand are the specifications. If x represents the number of fish caught in one year, is the specification to maximize total profit based on:

x_i+0, x_i+1, x_i+2, ....... x_i+9 based on the x_i being *all equal* or 10 separate values?

0

Featured Post

There are many ways to learn to code these days. From coding bootcamps like Flatiron School to online courses to totally free beginner resources. The best way to learn to code depends on many factors, but the most important one is you. See what course is best for you.

Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…

Aerodynamic noise is the cause of the majority of the noise produced by helicopters. The inordinate amount of noise helicopters produce is a major problem in the both a military and civilian setting. To remedy this problem the use of an aerogel coat…

The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…

The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.