On Wednesday, March 25, 2015 at 11:23:08 AM UTC+5:30, Paul Rubin wrote:
> kai.peters writes
> > 1 bit images of a size of 1024 x 1280 need to be processed this way,
> > so 1310720 list elements. Also needs to be 2.7 only.
>
> Where are these lists going to come from? Files? Process the file
> differently, probably. Use generators instead of lists, maybe.
Some C-ish solutions and then two loop-unrollings:
def foo(lst):
i = 0
while i < len(lst):
acc = 0
for j in range(8):
acc = 2*acc+lst[i]
i += 1
yield acc
def bar(lst):
i = 0
while i < len(lst):
acc = 0
acc = 2*acc+lst[i]
acc = 2*acc+lst[i+1]
acc = 2*acc+lst[i+2]
acc = 2*acc+lst[i+3]
acc = 2*acc+lst[i+4]
acc = 2*acc+lst[i+5]
acc = 2*acc+lst[i+6]
acc = 2*acc+lst[i+7]
i += 8
yield acc
def baz(lst):
i = 0
while i < len(lst):
acc = (128*lst[i] + 64*lst[i+1] + 32*lst[i+2] + 16*lst[i+3] +
8*lst[i+4] + 4*lst[i+5] + 2*lst[i+6] + lst[i+7])
i += 8
yield acc
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