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<p class="MsoNormal">Hi Kshitij,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I started modifying my code based on your advice. I have a question before I start digging more into intense modifications!
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In the stripped code posted below, the method GenerateResidualTape has the index i, j and k as arguments. Internally, there are many advector that use the index as adouble. As you can see, the array W (the independent variables) changes
as a function of i, j and k (GetPrimitives). So far, so good. But how about all the other internal advectors that depend on the indices? How can the call to sparse_jac know about those changed indices (apart from W obviously)? For example, I have an advector
of face areas. In GenerateResidualTape, I retrieve the areas of a given I,j,k. On the next iteration, I want the jacobian with respect to the new areas from the advector.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Thank you for your time,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Antoine<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> int cnt=0;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> for (adouble k=2;k<mNmax[2]-2;k++)
<b><span style="color:#4F6228;mso-style-textfill-fill-color:#4F6228;mso-style-textfill-fill-alpha:100.0%">// i, j and k used to be int</span></b><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> for (adouble j=2;j<mNmax[1]-2;j++)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> for (adouble i=2;i<mNmax[0]-2;i++)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> int ret;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (cnt!=0)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> {
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> mpStencil->GetPrimitives(i,j,k,W);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> ret = sparse_jac(mTag, m, n, 0, W, &nnz, &rind, &cind, &values, options);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(rind); rind=NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(cind); cind=NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(values); values=NULL;
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if ( (cnt==0) || (ret!=3))<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> {
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> GenerateResidualTape(i,j,k);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> mpStencil->GetPrimitives(i,j,k,W);
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> ret = sparse_jac(mTag, m, n, 0, W, &nnz, &rind, &cind, &values, options);
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(rind); rind=NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(cind); cind=NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> free(values); values=NULL;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> cnt++;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">----------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Hello,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">advector can indeed deal with changing indices in an array at a<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">different evaluation point.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">The constructor advector(const std::vector<adouble>& v) will indeed copy<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">the elements. This is standard practice when dealing with STL classes.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">If it did not copy then there would be the chance of some other part of<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">the code changing the memory contents from under the STL-container, and<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">there would be no warning for this.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">The easiest way to do this efficiently is to construct the advector<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">using advector(size_t n) and then assigning the elements using the<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">operator [](size_t i) or using a dynamic_cast<vector<adouble>& >() to<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">access the std::vector inside the advector. This would avoid copying.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">You anyway need to assign the elements at some point.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">The index for accessing the elements, which may change at a different<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">evaluation point must however be an adouble or an expression with<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">adoubles and the indexing is done with operator [](const badouble& i)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Hope this helps<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">Kshitij<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">As on 2013-03-22 22:24, Antoine De Blois did write:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> Hi everyone,<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i>
<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> I was trying to find a way to avoid retaping when the index of an array changes for a different taping point. I found today the advector, which sounds very promising for my
application.<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i>
<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> I want to have the advector 's as members of a class and I want to efficiently construct the advector. I don't think that the<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> advector(const std::vector<adouble>& v) will be efficient due to the involved copies. Is it done this way to avoid the lvalue issue?<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i>
<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> Is there any C++ code example someone is willing to share? I tried to search quickly on the web but I could not find any. This article confirms that ADOL-C can do what I want:<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> "Computing derivatives in a meshless simulation using permuation in ADOL-C." Kulshreshtha<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i>
<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> Thank you for your time,<o:p></o:p></i></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">><i> A</i><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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