One thing I'd like to see us do is create a set of reference files for the community to use when benchmarking. I picked my three from Howard's samples pile more or less at random, but I'd like to make sure we have a set that includes one with RGB data, one with nicely ordered points, one with horribly ordered points, one with waveforms, etc. Thoughts?
(Note this is not the same as a creating compliance or correctness reference set, which would include one 1.2 file, one 1.3 file, one file with icky VLRs, etc. Although clearly that would be a Good Thing to do also.) Also, it's already been suggested that a subsequent version of las2las support a "-o null" convention to remove some of the I/O overhead. -mpg From: [email protected] [mailto:[email protected]] On Behalf Of Michael Rosen Sent: Wednesday, February 02, 2011 11:24 AM To: [email protected] Subject: [Liblas-devel] LAZ / LAS extraction performance ... why does scene size make a difference? I also ran some benchmarks on laz and yes, MG4. Id like to be able to collaborate with some of you on this effort. I think MPGs comments about the different target workflows are spot on. For now, I do have an interesting observation about LAS and LAZ: in both cases there seems to be a linear relationship between the cropped area the time it takes to do the extraction. That would be expected if either (a) there was some indexing support that told us where in the file the points were. But I dont believe there is any. (b) The process was dominated by output latency. But Im not creating output (specifying -o which is what thats for I assume) Absent either of those factors I would have expected the extraction time to be roughly constant a full scan through the file and pick out the points we care about. So, why is it doing this? In both graphs, Y is time in seconds. In the first graph, X is the fraction of the total file cropped out. In the second, X is the number of points actually extracted. To test, I installed OSGeo4W and ran las2las on increasingly large crop areas from the center of MtStHelens.laz and .las (I encoded my own, but sample are available from http://liblas.org/samples. Heres the script I used: TimeThis las2las -e 1210343.88937174,315410.054252848,1215428.96062826,323308.825747152 -i MtStHelens.las -o - TimeThis las2las -e 1209290.7366317,313774.165113335,1216482.1133683,324944.714886665 -i MtStHelens.las -o - TimeThis las2las -e 1208482.6241118,312518.903227245,1217290.2258882,326199.976772755 -i MtStHelens.las -o - TimeThis las2las -e 1207801.35374348,311460.668505697,1217971.49625652,327258.211494303 -i MtStHelens.las -o - TimeThis las2las -e 1207201.1425,310528.345,1218571.7075,328190.535 -i MtStHelens.las -o - TimeThis las2las -e 1206658.51005792,309685.460122058,1219114.33994208,329033.419877942 -i MtStHelens.las -o - TimeThis las2las -e 1206159.50802811,308910.347481574,1219613.34197189,329808.532518426 -i MtStHelens.las -o - TimeThis las2las -e 1205695.0482634,308188.89022667,1220077.8017366,330529.98977333 -i MtStHelens.las -o - TimeThis las2las -e 1205258.81811523,307511.282758545,1220514.03188477,331207.597241455 -i MtStHelens.las -o - TimeThis las2las -e 1204846.22138258,306870.385680395,1220926.62861742,331848.494319605 -i MtStHelens.las -o - TimeThis las2las -e 1204453.78830496,306260.80932432,1221319.06169504,332458.07067568 -i MtStHelens.las -o - TimeThis las2las -e 1204078.82322361,305678.36645449,1221694.02677639,333040.51354551 -i MtStHelens.las -o - TimeThis las2las -e 1203719.18242262,305119.727182058,1222053.66757738,333599.152817942 -i MtStHelens.las -o - TimeThis las2las -e 1203373.12778539,304582.19164595,1222399.72221461,334136.68835405 -i MtStHelens.las -o - TimeThis las2las -e 1203039.22685462,304063.534773533,1222733.62314538,334655.345226467 -i MtStHelens.las -o - TimeThis las2las -e 1202716.28248697,303561.897011393,1223056.56751303,335156.982988607 -i MtStHelens.las -o - TimeThis las2las -e 1202403.2820478,303075.705408185,1223369.5679522,335643.174591815 -i MtStHelens.las -o - TimeThis las2las -e 1202099.3598951,302603.615340005,1223673.4901049,336115.264659995 -i MtStHelens.las -o - TimeThis las2las -e 1201803.76913607,302144.466639106,1223969.08086393,336574.413360894 -i MtStHelens.las -o - TimeThis las2las -e 1201515.86,301697.25,1224256.99,337021.63 -i MtStHelens.las -o - _______________________________________________ Liblas-devel mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/liblas-devel
