<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>Hello Bhrett,</div><div><br></div><div>Could you send the entire CMPL model directly to me (mike.steglich at <a href="http://th-wildau.de">th-wildau.de</a>)? It would makes it easier to find the problem.</div><div><br></div><div>Thanks,</div><div><br></div><div>Mike</div><div><br>Am 15.11.2017 um 20:52 schrieb Ogden, Bhrett A. <<a href="mailto:ogdenba@cdmsmith.com">ogdenba@cdmsmith.com</a>>:<br><br></div><blockquote type="cite"><div>
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<p class="MsoNormal">Thank you for your prompt answer to my last question. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have another question regarding syntax of CMPL. I have a power function that represents a route cost that I would like to linearize. I am using linear approximation to consider the range of options and break the non-linear equation into
a four-part piece-wise equation, f(x) ~= f(n) + f’(n)(x-n), where n is the mean route tonnage in the interval. The power function is C = e^a * x^b where a and b are constants that depend on the route origin/destination and x is the route tonnage. One element
that I am trying to minimize is the sum of the transport costs. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have approximated the cost to f(x) = e^a * n^b * (1 + b * n^-1 * x – b), where n is the mean route tonnage in the interval and a and b are constants with respect to the route. Assuming that all tonnages lie within the first interval for
now (to avoid complicating this question with piece-wise syntax), how can I represent this in CMPL? I was having issues with using parenthesis so I have done all of the distributions. Now I am receiving syntax errors about ^. What is the proper way to represent
this?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">transport_cost$1$ {<o:p></o:p></p>
<p class="MsoNormal">e in export_ports,<o:p></o:p></p>
<p class="MsoNormal">i in import_ports,<o:p></o:p></p>
<p class="MsoNormal">s in seasons,<o:p></o:p></p>
<p class="MsoNormal">g in grains,<o:p></o:p></p>
<p class="MsoNormal">r in route_type: <o:p></o:p></p>
<p class="MsoNormal">transport_cost[e,i,r,s,g] = exp(a[e,i]) * mean_tonnage_for_interval[1,s,g] ^ b[e,i] + b[e,i] * exp(a[e,i]) * route_tonnage[e,i,r,s,g] * mean_tonnage_for_interval[1,s,g] ^ b[e,i] * mean_tonnage_for_interval[1,s,g] ^ -1 - exp(a[e,i])* b *
mean_tonnage_for_interval[1,s,g] ^ b[e,i];<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Would you also be able to explain why I get a syntax error if I divide in the following situation?:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">tonnage_intervals$1$ {<o:p></o:p></p>
<p class="MsoNormal">s in seasons,<o:p></o:p></p>
<p class="MsoNormal">g in grains,<o:p></o:p></p>
<p class="MsoNormal">i in approximation_intervals:<o:p></o:p></p>
<p class="MsoNormal">tonnage_intervals[i,s,g] = worldwide_demand[s,g] * i * 1/len(approximation_intervals); # Division won't work. I'm having to hardcode 0.25 for now.<o:p></o:p></p>
<p class="MsoNormal">}<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you for your assistance.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best,<o:p></o:p></p>
<p class="MsoNormal">Bhrett Ogden<o:p></o:p></p>
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