ENH: halve the memory requirement of np.cov
ENH: halve the memory requirement of np.cov

Prevents allocation of an n²-sized array.

XXX For large arrays, multiplying by 1/fact is more than 10% faster
than dividing by fact, but that doesn't pass the tests.

SiccarPoint/numpy,bertrand-l/numpy,SiccarPoint/numpy,mattip/numpy,seberg/numpy,behzadnouri/numpy,bringingheavendown/numpy,bringingheavendown/numpy,ContinuumIO/numpy,pizzathief/numpy,rherault-insa/numpy,pizzathief/numpy,joferkington/numpy,endolith/numpy,WillieMaddox/numpy,ssanderson/numpy,ViralLeadership/numpy,gfyoung/numpy,pdebuyl/numpy,Eric89GXL/numpy,ViralLeadership/numpy,bertrand-l/numpy,argriffing/numpy,simongibbons/numpy,pyparallel/numpy,jonathanunderwood/numpy,grlee77/numpy,rgommers/numpy,bertrand-l/numpy,pbrod/numpy,njase/numpy,moreati/numpy,nbeaver/numpy,abalkin/numpy,joferkington/numpy,chatcannon/numpy,pdebuyl/numpy,b-carter/numpy,AustereCuriosity/numpy,cjermain/numpy,jonathanunderwood/numpy,MSeifert04/numpy,pdebuyl/numpy,madphysicist/numpy,stuarteberg/numpy,mwiebe/numpy,dwillmer/numpy,ahaldane/numpy,mwiebe/numpy,tynn/numpy,simongibbons/numpy,endolith/numpy,WarrenWeckesser/numpy,gfyoung/numpy,mhvk/numpy,madphysicist/numpy,seberg/numpy,groutr/numpy,MSeifert04/numpy,Dapid/numpy,ChristopherHogan/numpy,anntzer/numpy,Dapid/numpy,ddasilva/numpy,skwbc/numpy,simongibbons/numpy,mhvk/numpy,maniteja123/numpy,argriffing/numpy,shoyer/numpy,skwbc/numpy,jakirkham/numpy,maniteja123/numpy,MSeifert04/numpy,utke1/numpy,abalkin/numpy,simongibbons/numpy,pyparallel/numpy,solarjoe/numpy,AustereCuriosity/numpy,chiffa/numpy,njase/numpy,gmcastil/numpy,dwillmer/numpy,madphysicist/numpy,madphysicist/numpy,chatcannon/numpy,pbrod/numpy,mattip/numpy,argriffing/numpy,ahaldane/numpy,numpy/numpy,kiwifb/numpy,WillieMaddox/numpy,solarjoe/numpy,jorisvandenbossche/numpy,jonathanunderwood/numpy,tacaswell/numpy,gmcastil/numpy,charris/numpy,Dapid/numpy,kiwifb/numpy,seberg/numpy,groutr/numpy,gmcastil/numpy,njase/numpy,jorisvandenbossche/numpy,jakirkham/numpy,cjermain/numpy,ViralLeadership/numpy,rherault-insa/numpy,pdebuyl/numpy,ContinuumIO/numpy,rgommers/numpy,ssanderson/numpy,pizzathief/numpy,endolith/numpy,skwbc/numpy,joferkington/numpy,mattip/numpy,shoyer/numpy,charris/numpy,WarrenWeckesser/numpy,jakirkham/numpy,stuarteberg/numpy,dwillmer/numpy,numpy/numpy,pbrod/numpy,pbrod/numpy,nbeaver/numpy,groutr/numpy,shoyer/numpy,jorisvandenbossche/numpy,chiffa/numpy,mwiebe/numpy,jakirkham/numpy,numpy/numpy,tynn/numpy,WillieMaddox/numpy,MSeifert04/numpy,grlee77/numpy,ChristopherHogan/numpy,stuarteberg/numpy,madphysicist/numpy,drasmuss/numpy,mhvk/numpy,mhvk/numpy,ahaldane/numpy,grlee77/numpy,drasmuss/numpy,rherault-insa/numpy,abalkin/numpy,Eric89GXL/numpy,ChristopherHogan/numpy,WarrenWeckesser/numpy,ssanderson/numpy,moreati/numpy,ESSS/numpy,leifdenby/numpy,shoyer/numpy,ChristopherHogan/numpy,pizzathief/numpy,WarrenWeckesser/numpy,tynn/numpy,ESSS/numpy,pizzathief/numpy,stuarteberg/numpy,SiccarPoint/numpy,moreati/numpy,jorisvandenbossche/numpy,ddasilva/numpy,pyparallel/numpy,cjermain/numpy,anntzer/numpy,ddasilva/numpy,simongibbons/numpy,charris/numpy,behzadnouri/numpy,Eric89GXL/numpy,AustereCuriosity/numpy,pbrod/numpy,leifdenby/numpy,joferkington/numpy,kiwifb/numpy,jorisvandenbossche/numpy,solarjoe/numpy,tacaswell/numpy,behzadnouri/numpy,mattip/numpy,rgommers/numpy,bringingheavendown/numpy,tacaswell/numpy,SiccarPoint/numpy,jakirkham/numpy,anntzer/numpy,Eric89GXL/numpy,ahaldane/numpy,drasmuss/numpy,grlee77/numpy,shoyer/numpy,MSeifert04/numpy,cjermain/numpy,utke1/numpy,numpy/numpy,b-carter/numpy,leifdenby/numpy,grlee77/numpy,nbeaver/numpy,gfyoung/numpy,b-carter/numpy,charris/numpy,rgommers/numpy,maniteja123/numpy,ahaldane/numpy,endolith/numpy,mhvk/numpy,dwillmer/numpy,chiffa/numpy,ESSS/numpy,ContinuumIO/numpy,WarrenWeckesser/numpy,seberg/numpy,anntzer/numpy,chatcannon/numpy,utke1/numpy