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# a solution for N=1000 to
# https://projecteuler.net/problem=14
# we use a fast local array to
# memoize small collatz numbers
#
# todo, insert sign extensions

@start
	%mem  =l alloc4 4000

@loop
	%n    =w phi @start 1, @newm %n9, @oldm %n9
	%cmax =w phi @start 0, @newm %c,  @oldm %cmax

	%fin  =w cslt %n, 1000
	jnz %fin, @cloop, @end

@cloop
	%n0   =w phi @loop %n, @odd %n2, @even %n3
	%c0   =w phi @loop 0,  @odd %c1, @even %c1

	%is1  =w ceq %n0, 1
	jnz %is1, @endcl, @iter0

@iter0
	%ism  =w cslt %n0, %n
	jnz %ism, @getmemo, @iter1   # we have it in the table

@iter1
	%c1   =w add %c0, 1
	%p    =w and %n0, 1
	jnz %p, @odd, @even

@odd
	%nn   =w add %n0, %n0        # compute %n2 = 3 * %n0 + 1
	%n1   =w add %n0, %nn
	%n2   =w add %n1, 1
	jmp @cloop

@even
	%n3   =w div %n0, 2          # %n3 = %n0 / 2
	jmp @cloop

@getmemo
	%idx00 =l add %n0, %n0
	%idx0  =l add %idx00, %idx00
	%loc0  =l add %idx0, %mem
	%cn0   =w load %loc0
	%c2  =w add %c0, %cn0

@endcl
	%c     =w phi @getmemo %c2, @cloop %c0

	%idx10 =l add %n, %n
	%idx1  =l add %idx10, %idx10
	%loc1  =l add %idx1, %mem
	storew %c, %loc1             # memorize the result
	%n9    =w add 1, %n
	%big   =w csle %cmax, %c
	jnz %big, @newm, @oldm

@newm
	jmp @loop
@oldm
	jmp @loop

@end
	storew %cmax, $a
	ret