Hi everybody, the tiny iOS app I work on currently begins by decoding 3D data in the form of a TIN: vertices, normals then triangles. There are about 200 000 of the two formers, and 400 000 of the latters (needless to say, at a later stage, I am going to improve speed by using some kind of tiling and mipmaping at the geometric level, though I am getting surprisingly good performance with this crude model, even on an iPhone 4, i.e. ca 15 fps). The syntax of the TIN file is very simple: coma separated components, and a specific header for each of the three sections.
At first, the TIN file didn’t include the exact number of vertices/normals/triangles, so I had to decode the whole file in order to know how large a buffer I should allocate to store each of the three data types. Meanwhile I did record the data in NSMutableArrays. But I ended up eating more than 200 MB of memory doing so, even with ARC enabled! > 200 MB for three mutable arrays, each with a corresponding number of arrays of three strings each (the original TIN file is about 17 MB). Needless to say, that was more than excessive. Thus, I backed off, decided to add the number of primitives in the file header, in order to be able to use malloc right after the beginning of the process, and substituted all Obj-C oriented calls by plain C functions (e.g. instead of [myMutableArray add:[[NSString stringFromCString:… encoding:…] componentsSeparatedBy:@", "]], I just wrote: sscanf (myLine, "%f, %f, %f", &t [0], &t [1], &t [2])) and this time, the memory usage didn’t top 21 MB, which seems reasonable. How come I get such a large discrepancy in memory usage between the two solutions? Is the overhead of Cocoa object so huge? Thanks! Vincent _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
