Mailing List Archive

Hello,
Below is very simple cache implementation. There is no LRU, MRU,
no predictor or other features. Nothing but cache.
I'm interested in improvements to this code. It could
be useful - not only for me, I hope :-)
Rafal Smotrzyk

#code-start
import whrandom

class MSimpleCache:
def __init__(self,agetfunc,amaxlen=100):
self.GetValue=agetfunc
self.MaxLen=amaxlen
self.VDict={}
self.KDict={}
self.VPos=1
self.AccessRatio=0
self.HitRatio=0
def __getitem__(self,key):
self.AccessRatio=self.AccessRatio+1
id=self.KDict.get(key,0)
if id:
self.HitRatio=self.HitRatio+1
return self.VDict[id][1]
else:
v=self.VDict.get(self.VPos,0)
if v:
del self.KDict[v[0]]
ret=self.GetValue(key)
self.VDict[self.VPos]=[key,ret]
self.KDict[key]=self.VPos
self.VPos=self.VPos+1
if self.VPos>self.MaxLen:
self.VPos=1
return ret
def dump(self):
print 'Access ratio:',self.AccessRatio
print 'Hit ratio:',self.HitRatio
print 'Hit %:',100.0*self.HitRatio/self.AccessRatio
print 'VDict len:',len(self.VDict.keys())
print 'KDict len:',len(self.KDict.keys())

# cached operation - sample
def GetCalculatedValue(key):
x=`key`+'aaaa'
y=key*0.5
z=x+`y`
return z

# models of distribution max=1000 def GetLinear(key): return key def
GetRandom(key): return whrandom.randint(1,max)
l1,l2,l3=whrandom.randint(1,max),whrandom.randint(1,max),whrandom.randint(1,m
ax) def GetNDist(key): global l1,l2,l3
l1,l2,l3=l2,l3,whrandom.randint(1,max) return int((l1+l2+l3)/3)

#test...
for aname,afunc in
[['Linear',GetLinear],['Random',GetRandom],['NDist',GetNDist]]:
acache=MSimpleCache(GetCalculatedValue,250)
for i in range(1000):
k=afunc(i)
x=acache[k]
y=GetCalculatedValue(k)
if x!=y:
print 'ValueError:',k,x,y
print 'Name:',aname
acache.dump()
print

#code-end

#output-start
Name: Linear
Access ratio: 1000
Hit ratio: 0
Hit %: 0.0
VDict len: 250
KDict len: 250

Name: Random
Access ratio: 1000
Hit ratio: 221
Hit %: 22.1
VDict len: 250
KDict len: 250

Name: NDist
Access ratio: 1000
Hit ratio: 355
Hit %: 35.5
VDict len: 250
KDict len: 250
#output-end

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