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Memory leak in StringSplit in Mathematica 7

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97255] Memory leak in StringSplit in Mathematica 7
  • From: Scott Morrison <scott.morrison at gmail.com>
  • Date: Mon, 9 Mar 2009 01:06:19 -0500 (EST)

I'm on OSX 10.5, running Mathematica 7. There's apparently a memory leak in
StringSplit -- 16 bytes get used up every call. See below for a "by
hand" implementation of StringSplit, and two test runs showing the
difference.

The problem had caused big problems; a long run of one of my programs
was mysteriously starting to page memory unnecessarily, and switching
to the "by hand" implementation fixes the problem.

In[135]:= StringSplitWithoutMemoryLeak[S_,V_]:=StringTake[S,#]&/
@Partition[{1}~Join~Flatten[#+{-1,1}&/@StringPosition[S,V]]~Join~{-1},
2]
In[145]:= StringSplitWithoutMemoryLeak["12341234","2"]==StringSplit
["12341234","2"]
Out[145]= True
In[137]:= randomString:=StringJoin@@RandomChoice[{"0,","1","2"},10]
In[143]:= Do[Print["Memory in use: ",MemoryInUse[]];Print["Time for
100000 StringSplits: ",AbsoluteTiming[Do[StringSplit[randomString,"0"],
{100000}]][[1]]],{4}]
During evaluation of In[143]:= Memory in use: 130297096
During evaluation of In[143]:= Time for 100000 StringSplits: 1.312322
During evaluation of In[143]:= Memory in use: 131897496
During evaluation of In[143]:= Time for 100000 StringSplits: 1.345231
During evaluation of In[143]:= Memory in use: 133497496
During evaluation of In[143]:= Time for 100000 StringSplits: 1.314813
During evaluation of In[143]:= Memory in use: 135097496
During evaluation of In[143]:= Time for 100000 StringSplits: 1.403105
In[144]:= Do[Print["Memory in use: ",MemoryInUse[]];Print["Time for
100000 StringSplits: ",AbsoluteTiming[Do[StringSplitWithoutMemoryLeak
[randomString,"0"],{100000}]][[1]]],{4}]
During evaluation of In[144]:= Memory in use: 136701120
During evaluation of In[144]:= Time for 100000 StringSplits: 3.918605
During evaluation of In[144]:= Memory in use: 136701480
During evaluation of In[144]:= Time for 100000 StringSplits: 3.948706
During evaluation of In[144]:= Memory in use: 136701480
During evaluation of In[144]:= Time for 100000 StringSplits: 3.952957
During evaluation of In[144]:= Memory in use: 136701480
During evaluation of In[144]:= Time for 100000 StringSplits: 3.916070


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