id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,cpu,platform 438,v.distance -a uses too much memory,mlennert,grass-dev@…,"Not sure if this should be considered as a bug or a wish for enhancement...chosing bug for now as it makes the module useless with large files. When trying to calculate a distance matrix between 20 000 points with v.distance -a, I get: ERREUR:G_realloc: unable to allocate 1985321728 bytes at main.c:568 As the machine only has 1 GB of RAM, this is normal, but v.distance should be rewritten to not keep everything in memory, at least when dealing with the -a flag, and to only allocate memory for data really requested. Currently, it allocates memory for a large number of NEAR structures (3xint+10xdouble i.e., for example, 3x4+10x8=92Bytes for each point) which contain space for all the potential uplad options (lines 447-8 of vector/v.distance/main.c): {{{ anear = 2 * nfrom; Near = (NEAR *) G_calloc(anear, sizeof(NEAR)); }}} And then goes on to if necessary add memory space for the entire From x To matrix (lines 566-8 of vector/v.distance/main.c) in the loop of the to objects (count= total number of distances calculated after each loop): {{{ if (anear <= count) { anear += 10 + nfrom / 10; Near = (NEAR *) G_realloc(Near, anear * sizeof(NEAR)); }}} I'm not sure I completely understand this last part, as it seems to create huge jumps in allocation, i.e. when the count of distances goes beyond nfrom*2 (or later values of anear), it reallocates memory space for anear new NEARS. In my case, when count>40000, anear=40000+10+20000/10=42010, i.e. adding space for 2010 new NEAR structures, without knowing (AFAICT) how many will actually still come... But, as I said, I don't understand the code well enough to make a definite judgement. It would seem, however, that it might be better to calculate each distance and update the table immediately, or maybe write the necessary queries to a temp file to be able to launch the query at the end in one run, but without keeping everything in memory. ",defect,new,major,7.8.3,Vector,svn-trunk,,v.distance memory allocation,,Unspecified,Unspecified