Scope storage class

[bearophile]

Sergey Gromov:
> Remove -inline from your compiler options, and #2 compiles and runs
> faster in both D1 and D2 than #1.
> lazy seems to do something funny when -inline is in effect.

You are right, I have tested it on D1.
I think the codepad doesn't use -inline, that's why #2 works there.
#2 also uses less RAM on D1, for example N=24 requires about 707 MB instead of 788 MB, and about 2.8 s instead of about 3 s.

Sergey Gromov:
> Remove -inline from your compiler options, and #2 compiles and runs
> faster in both D1 and D2 than #1.
> lazy seems to do something funny when -inline is in effect.

You are right, I have tested it on D1.
I think the codepad doesn't use -inline, that's why #2 works there.

#2 also uses less RAM on D1, for example N=24 requires about 710 MB instead of 788 MB, and about 2.8 s instead of about 3 s.

This is the Asm of the #2 compiled with D1 with -O -release, it's shorter still (but note there are some other parts that I don't show here):

_D11man_or_boy21aFiLiLiLiLiLiZi	comdat
	assume	CS:_D11man_or_boy21aFiLiLiLiLiLiZi
L0:		push	EAX
		push	EBX
		cmp	dword ptr 034h[ESP],0
		jg	L33
		mov	EAX,014h[ESP]
		mov	EDX,018h[ESP]
		mov	EBX,014h[ESP]
		call	EDX
		push	EAX
		sub	ESP,4
		mov	EAX,014h[ESP]
		mov	EDX,018h[ESP]
		mov	EBX,014h[ESP]
		call	EDX
		mov	ECX,EAX
		add	ESP,4
		pop	EAX
		add	EAX,ECX
		jmp short	L3C
L33:		lea	EAX,4[ESP]
		call	near ptr _D11man_or_boy21aFiLiLiLiLiLiZi1bMFZi
L3C:		pop	EBX
		pop	ECX
		ret	02Ch
_D11man_or_boy21aFiLiLiLiLiLiZi	ends

--------------------------

I have then tested #1 and #2 without -inline on D2, and the results are very different from each other: #1 is very slow and uses lot of memory, while #2 (that contains no scope) acts as D1, using "only" 707 MB with N=24 and working with n=25 too. The asm code is similar the one I have just shown here.
So compiling #2 witout -inline in D2 fulfulls my original desire of computing up to N=25 with D2 :-)

I presume the -inline uncovers a small bug of DMD, that will be fixed. But what interests me more now is to understand how to write such fast code in general in D2.

Bye,
bearophile