Thom Posted March 24, 2009 Share Posted March 24, 2009 After many calls to tech, reducing the number of loci to less than 750 loci, I still cannot predict if the process will work. At best it takes 45 min. A civil engineer friend allowed me to set the model up in Civil 3D and it took 3 min. to run the calc. We need some new, efficient code. Quote Link to comment
0 islandmon Posted March 24, 2009 Share Posted March 24, 2009 DTM > Cut&Fill approximates comparisons between polyline sections. If those polylines have tonnes of vertices then the calculations can take quite awhile, indeed. Prior to beginning any DTM process setting the 2d/3d conversions to low or medium will speed things up. Additionally, the grid spacing is critical... an overly aggressive small grid will stress the calculations unnecessarily. Setting the contour grid to the largest possible value is highly beneficial. It could just be that Civil 3D defaults to the lowest possible set of relationships in order to optimize the calculation overhead while producing a reliable approximation of the Cut & Fill volumes. Quote Link to comment
0 brudgers Posted March 25, 2009 Share Posted March 25, 2009 Given that even the slowest Core2 CPU's run at several GFLOPS per core, this appears to be an algorithm issue...even assuming only an effective one GFLOP per core 45minutes is more than one trillion FLOPS [100% efficiency @ 1 GFLOP = 2.7 x 10^12 flops/45 minutes]. In a scenario of 1000 poly lines with 1000 points each, and requiring 1000 flops per point, there are only 10^9 flops required. Quote Link to comment
0 Thom Posted March 25, 2009 Author Share Posted March 25, 2009 As I noted above, I have stripped the polylines and loci to the bare minimum that I deem reliable for this 5 acre site. I ran a rebuilt, "clean" dtm last night and it took 1.5 hours to complete the task. I did check with my civil to see what his setting were for civil 3D and they were set much tighter as he says he is fairly anal about calcs. Quote Link to comment
0 brudgers Posted March 25, 2009 Share Posted March 25, 2009 [1.0 x 10^9 flop/750 loci] x [60 secs] x [45] = 3.6*10^9 flops/loci Those are AIG numbers. Quote Link to comment
Question
Thom
After many calls to tech, reducing the number of loci to less than 750 loci, I still cannot predict if the process will work. At best it takes 45 min.
A civil engineer friend allowed me to set the model up in Civil 3D and it took 3 min. to run the calc.
We need some new, efficient code.
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