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It does indeed clear the array, but it does not free it the underlying buffer.

Setting $#a extends the visible size of the array, not just the internal one. The elements I proceeded to push onto the array were getting added after the 12 mil empty ones.

@a=(); empties the visible array, but doesn't deallocate the internal buffer like undef @a; does.

$ perl -MDevel::Peek -e' my @a = qw( a b c ); Dump(\@a,1); @a=(); Dump(\@a,1); undef(@a); Dump(\@a,1); ' SV = IV(0x816ce54) at 0x816ce58 REFCNT = 1 FLAGS = (TEMP,ROK) RV = 0x817bc50 SV = PVAV(0x816d038) at 0x817bc50 REFCNT = 2 FLAGS = (PADMY) ARRAY = 0x817b500 FILL = 2 <---- 3 elements MAX = 3 <---- 4 slots ARYLEN = 0x0 FLAGS = (REAL) SV = IV(0x816c154) at 0x816c158 REFCNT = 1 FLAGS = (TEMP,ROK) RV = 0x817bc50 SV = PVAV(0x816d038) at 0x817bc50 REFCNT = 2 FLAGS = (PADMY) ARRAY = 0x817b500 FILL = -1 <---- 0 elements MAX = 3 <---- 4 slots ARYLEN = 0x0 FLAGS = (REAL) SV = IV(0x816c154) at 0x816c158 REFCNT = 1 FLAGS = (TEMP,ROK) RV = 0x817bc50 SV = PVAV(0x816d038) at 0x817bc50 REFCNT = 2 FLAGS = (PADMY) ARRAY = 0x0 <---- No array allocated FILL = -1 <---- 0 elements MAX = -1 <---- 0 slots ARYLEN = 0x0 FLAGS = (REAL)

If you don't want to rely on that, you could do

my @lines; $#lines = 12_000_000; $lines[$.-1] = $_ while <>; $#lines = $.-1;

In reply to Re^5: mem usage by ikegami
in thread mem usage by halfcountplus

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