North Carolina sample dataset
test from
http://lists.osgeo.org/pipermail/grass-dev/2009-July/045152.html
modified to get a larger region
g.region rast=elev_state_500m@PERMANENT res=100
# gives about 28 million cells
v.to.rast nc_state@PERMANENT use=val val=500.0 out=cost --o
v.to.rast urbanarea@PERMANENT use=val val=1 out=urbanarea --o
r.cost in=cost start_rast=urbanarea out=dist_urban percent_memory=20 --o
grass7 r.cost
real 0m55.349s
user 0m53.360s
sys 0m1.797s
grass65 r.cost
real 26m35.166s
user 2m55.612s
sys 23m37.921s
Results are identical. Reducing the memory percentage gives a hefty speed penalty in grass6, not so in grass7. Memory consumption is also a bit lower in grass7. IMO, 28 million cells is not a lot for today's standards, and I dare say r.cost is ready for massive datasets.
Enjoy,
Markus M