内置拉链功能速度 [英] built in zip function speed
问题描述
我希望我不是太无知：p但是这里......我的老板已经写了一些python代码并要求我为他加速...
我已经将运行时间从大约20分钟减少到13分钟（不错我认为
;）为了加快速度我要求他更换这样的循环： -
index = 0
元素中的元素：
av = a [index]
bv = b [index]
cv = c [index]
dv = d [index]
avbv =（av-bv） *（av-bv）
diff = cv - dv
e.append（diff - avbv）
index = index + 1
（其中a，b，c和d是200,000个元素浮点数组）
使用内置的zip函数..它似乎是为这个问题做的！
for av，bv，cv，dv in zip（a，b，c，d）：
avbv =（av-bv）*（av - bv）
diff = cv - dv
e.append（diff - avbv）
然而这似乎运行得多慢于*我*认为它会
（实际上比切片慢）我猜我要问的是..会不会是你希望这个
？
完整代码清单（我希望我有发了一个非常明显的错误）： -
导入数组
导入时间
a = array.array（" f"）
b = array.array（" f"）
c = array.array（" f"）
d = array.array（" ; f"）
e = array.array（" f"）
表示xrange（1，200000,1）中的值：
a.append（float（value））
b.append（float（value））
c.append（float（value））
d.append（float（value））
start = time.time（）
index = 0
元素中的元素：
av = a [index]
bv = b [index]
cv = c [index]
dv = d [index]
avbv =（av-bv）*（av-bv）
diff = cv - dv
e.append（diff - avbv）
index = index + 1
end0 =时间。时间（）
打印end0-start
e = array.array（" f"）
for av，bv，cv，dv in zip（a ，b，c，d）：
avbv =（av-bv）*（av - bv）
diff = cv - dv
e.append（diff - avbv）
end1 = time.time（）
print end1-end0
>
e = array.array（" f"）
##只是为了笑我自己的拉链功能
##笑话是它比内置拉链运行得更快？
def myzip（* args）：
index = 0
for elem in args [0]：
zipper = []
arg中arg的
：
zipper.append（arg [index]）
index = index +1
产量拉链
for my，bv，cv，dv myzip（a，b ，c，d）：
avbv =（av-bv）*（av - bv）
diff = cv - dv
e。追加（差异 - avbv）
end2 = time.time（）
打印end2-end1
$来自400万元素输入阵列的b $ b时间
切片：
8.77999997139
zip（）：
36.5759999752
myzip（ ）：
12.1449999809
itertools.izip通常比zip更快。你可以试试。
Rune Strand写道：
itertools.izip通常比zip更快。你可以试试。
非常感谢
时间为itertools.izip
for av ，bv，cv，dv in itertools.izip（a，b，c，d）：
avbv =（av-bv）*（av - bv）
diff = cv - dv
e.append（diff - avbv）
400万元素aray上的
：
切片：
8.06299996376
内置拉链：
36.5169999599
myzip：
12.0320000648
izip：
5.76499986649
如此快速整体
Rune Strand写道：
itertools.izip通常比zip更快。你可以试试。
非常感谢
时间为itertools.izip
for av ，bv，cv，dv in itertools.izip（a，b，c，d）：
avbv =（av-bv）*（av - bv）
diff = cv - dv
e.append（diff - avbv）
400万元素aray上的
：
切片：
8.06299996376
内置拉链：
36.5169999599
myzip：
12.0320000648
izip：
5.76499986649
如此快速整体
I hope I am not being too ignorant :p but here goes... my boss has
written a bit of python code and asked me to speed it up for him...
I''ve reduced the run time from around 20 minutes to 13 (not bad I think
;) to speed it up further I asked him to replace a loop like this:-
index = 0
for element in a:
av = a[index]
bv = b[index]
cv = c[index]
dv = d[index]
avbv = (av-bv) * (av-bv)
diff = cv - dv
e.append(diff - avbv)
index = index + 1
(where a, b, c and d are 200,000 element float arrays)
to use the built in zip function.. it would seem made for this problem!
for av, bv, cv, dv in zip(a, b, c, d):
avbv = (av-bv) * (av - bv)
diff = cv - dv
e.append(diff - avbv)
however this seems to run much slower than *I* thought it would
(and in fact slower than slicing) I guess what I am asking is.. would
you expect this?
full code listing (I hope I have made a very obvious error):-
import array
import time
a = array.array("f")
b = array.array("f")
c = array.array("f")
d = array.array("f")
e = array.array("f")
for value in xrange(1, 200000, 1):
a.append(float(value))
b.append(float(value))
c.append(float(value))
d.append(float(value))
start = time.time()
index = 0
for element in a:
av = a[index]
bv = b[index]
cv = c[index]
dv = d[index]
avbv = (av-bv) * (av-bv)
diff = cv - dv
e.append(diff - avbv)
index = index + 1
end0 = time.time()
print end0-start
e = array.array("f")
for av, bv, cv, dv in zip(a, b, c, d):
avbv = (av-bv) * (av - bv)
diff = cv - dv
e.append(diff - avbv)
end1 = time.time()
print end1-end0
e = array.array("f")
## just for a laugh my own zip function
## the joke is it runs faster than built in zip ??
def myzip(*args):
index = 0
for elem in args[0]:
zipper = []
for arg in args:
zipper.append(arg[index])
index = index +1
yield zipper
for av, bv, cv, dv in myzip(a, b, c, d):
avbv = (av-bv) * (av - bv)
diff = cv - dv
e.append(diff - avbv)
end2 = time.time()
print end2-end1
timings from 4 million element input array
slice:
8.77999997139
zip():
36.5759999752
myzip():
12.1449999809
itertools.izip is usually faster than zip. You can try that.
Rune Strand wrote:itertools.izip is usually faster than zip. You can try that.
Thanks very much
timing for itertools.izip
for av, bv, cv, dv in itertools.izip(a, b, c, d):
avbv = (av-bv) * (av - bv)
diff = cv - dv
e.append(diff - avbv)
on a 4 million element aray:
slice:
8.06299996376
built in zip:
36.5169999599
myzip:
12.0320000648
izip:
5.76499986649
so fastest overall
Rune Strand wrote:itertools.izip is usually faster than zip. You can try that.
Thanks very much
timing for itertools.izip
for av, bv, cv, dv in itertools.izip(a, b, c, d):
avbv = (av-bv) * (av - bv)
diff = cv - dv
e.append(diff - avbv)
on a 4 million element aray:
slice:
8.06299996376
built in zip:
36.5169999599
myzip:
12.0320000648
izip:
5.76499986649
so fastest overall
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