aspather is a small tool that reads in a  BGP table output from the Brocade / Extreme command
show ip bgp routes and calculates to a given target CAM size by filtering out AS  numbers.

With a list of preferred countries, a weighted list of personal required AS numbers and a default set, it can optimize till the last route. 
An example run with my preferred list will drop several files in the output list. 

My limit is here around 760.000 prefixes, so we keep a spare for internal routes and new prefixes. 

./aspather -camsize 760000 -routes fullroutes -personal config_personal  -debug
2020/06/27 10:04:15 Starting optimizer, target cam size 760000
input: 817765 routes in 98885 bgp autonomous systems
758305 in 0 zero 30899 match 67972 nospace 14 nospaceRoutes 59324
Routes not installed:
	 AS not seen in BGP: 30899
	 AS not enough CAM: 14
	 Not installed by country:
	IL:1 CA:1 AU:1 ES:1 MX:1 CR:1 SA:1 VN:2 US:3 TR:1 ID:1
ip as-path access-list savethefib permit _11492$
ip as-path access-list savethefib permit _11830$
ip as-path access-list savethefib permit _12479$
ip as-path access-list savethefib permit _22773$
ip as-path access-list savethefib permit _39891$
ip as-path access-list savethefib permit _45899$
ip as-path access-list savethefib permit _6327$
ip as-path access-list savethefib permit _7155$
ip as-path access-list savethefib permit _7545$
ip as-path access-list savethefib permit _7552$
ip as-path access-list savethefib permit _7713$
ip as-path access-list savethefib permit _8151$
ip as-path access-list savethefib permit _8551$
ip as-path access-list savethefib permit _9121$
2020/06/27 10:04:15 	Alloc = 152 MiB
2020/06/27 10:04:15 	TotalAlloc = 558 MiB
2020/06/27 10:04:15 	Sys = 205 MiB
2020/06/27 10:04:15 	NumGC = 26