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<div>Hi Everyone,</div>
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<div>My previous post was about different results on Hardware than on my laptop. I found out by trial and error that it seems related to the
<b>nlp_scaling_method</b>. </div>
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<li style="font-family: Tahoma; font-size: 10pt; ">When using a "gradient-based" I get nice results on Simulink (laptop), but on xPC-target (real-time hardware), I get some "Invalid number" or "restoration failed" message.</li><li><font size="2">When using "user-scaling" and not specify any scaling anywhere (I cannot find it in the 'options' appendix C of the documentation), Simulink and xPC-target show </font>similar<font size="2"> results, but much slower. </font><span style="font-family: Tahoma; font-size: 10pt; ">If
I look at the logs, the slower response does not come from the number of iterations, but from the number of function evaluations during </span><span style="font-family: Tahoma; font-size: 10pt; "><u>one</u></span><span style="font-family: Tahoma; font-size: 10pt; "> iteration.</span></li></ul>
<div>I am using a simple forward-difference approximation for the gradient with a static stepsize of h=1e-7 (machine accuracy of laptop is 2.22e-16, not sure about the xPC-target Intel Xeon).</div>
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<div>Two questions:</div>
<div><u>1. The high number of function evaluations per iteration seems to point to a gradient issue. Am I correct in this?</u></div>
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<div><u>2. Ideally I would like to use gradient-based scaling, but does anyone have any experience in using this method i.c.w. finite difference approximation?</u></div>
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<div>I hope someone can help me, because I am really lost in this for a week now. :)</div>
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<div>Best,</div>
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<div>Martijn Disse</div>
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<div id="divRpF988378" style="direction: ltr; "><font face="Tahoma" size="2" color="#000000"><b>Van:</b> ipopt-bounces@list.coin-or.org [ipopt-bounces@list.coin-or.org] namens Martijn Disse [M.W.Disse@student.tudelft.nl]<br>
<b>Verzonden:</b> dinsdag 2 oktober 2012 11:35<br>
<b>To:</b> ipopt@list.coin-or.org<br>
<b>Onderwerp:</b> [Ipopt] Issue on hardware implementation IPOPT: scaling issue?<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">Hi everyone,
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<div>I've build an NMPC controller as a Matlab C-mex S-function and it works like a charm in Simulink. When I however compile to an xPC-target (turn a PC into a dedicated hardware) executable using MSVS 2010 express, I get different results.</div>
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<div>I used the "output_file" option on to see what is happening. There are several differences between the Simulink log and the target hardware log:</div>
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<div>1. <span class="Apple-tab-span" style="white-space:pre"></span>Xpc: <span class="Apple-tab-span" style="white-space:pre">
</span>Scaling parameter for objective function = 1.000000e-008</div>
<div><span class="Apple-tab-span" style="white-space:pre"></span>Simulink: <span class="Apple-tab-span" style="white-space:pre">
</span>Scaling parameter for objective function = 1.163760e-003</div>
<div>2. <span class="Apple-tab-span" style="white-space:pre"> </span>Xpc: <span class="Apple-tab-span" style="white-space:pre">
</span>compl_inf = 4.0000000500000000e+005</div>
<div><span class="Apple-tab-span" style="white-space:pre"></span>Simulink: <span class="Apple-tab-span" style="white-space:pre">
</span>compl_inf = 3.4371342722094269e+000</div>
<div>3. <span class="Apple-tab-span" style="white-space:pre"> </span>Xpc:<span class="Apple-tab-span" style="white-space:pre">
</span>overall_error = 4.0000000499999999e-003</div>
<div><span class="Apple-tab-span" style="white-space:pre"></span>Simulink:<span class="Apple-tab-span" style="white-space:pre">
</span>overall_error = 1.0000000000000000e+002</div>
<div>Iteration 0:</div>
<div>4.<span class="Apple-tab-span" style="white-space:pre"> </span>Xpc:<span class="Apple-tab-span" style="white-space:pre">
</span>inf_du lg(mu) = 8.59e-004</div>
<div><span class="Apple-tab-span" style="white-space:pre"></span>Simulink:<span class="Apple-tab-span" style="white-space:pre">
</span>inf_du lg(mu) = 1.00e+002</div>
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<div>It ends up with:</div>
<div>-EXIT: Invalid number in NLP function or derivative detected.</div>
<div>-Restoration phase is called at point that is almost feasible, with constraint violation 5.672143e-007. Abort.</div>
<div>-EXIT: Restoration Failed!</div>
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<div>My question: <b>What could case a difference in the hardware implementation (xPC-target, Mathworks) and the Simulink results? The difference is already visible in the completely different scaling values.</b></div>
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<div>I hope someone can help me :)</div>
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<div>Best regards,</div>
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<div>-Martijn Disse</div>
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