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Memory leak or flawed garbage collector

  • To: mathgroup at
  • Subject: [mg120576] Memory leak or flawed garbage collector
  • From: "Fabrice P. Laussy" <fabrice.laussy at>
  • Date: Fri, 29 Jul 2011 08:03:01 -0400 (EDT)
  • Delivered-to:

Dear Group,

I have a problem of garbage collection or of memory leak, with a
module that will seemingly not discard its internal variables, thus
leading to explosion of memory usage by repeated calls to this module.

Opening the notebook, nothing else being done yet:

	In[1]:= MemoryInUse[]
	Out[1]= 18460176

Then I define the said module, with private variables, etc. Before
running the first instance of it, already there appears many
variables, some defined globally, others with the $ of internal

	A	coef	Disa$	g2	K\[Sigma]3$	L\[Sigma]1	mybasis	n\[Sigma]3	re$	X	\[Gamma]	\[Nu]\[Nu]	\[Omega]3$
	AllM	coefa	Dis\[Sigma]1	g3	L	L\[Sigma]1$	mybasis$	n\[Sigma]3$	solMean	Xsol	\[Gamma]1	\[Nu]\[Nu]\[Nu]	\[Omega]a
	AllM$	coefa$	Dis\[Sigma]1$	i	La	L\[Sigma]2	myvar	n$	solMean$	Xsol$	\[Gamma]2	\[Nu]\[Nu]\[Nu]$	\[Omega]a$
	Av	coef\[Sigma]1	eig	im	La$	L\[Sigma]2$	m\[CapitalDelta]	order	Spea	x$	\[Gamma]3	\[Nu]\[Nu]$	\[Omega]max
	Average	coef\[Sigma]1$	eigV	im$	lcor	L\[Sigma]3	m$	out	Spea$	X$	\[Gamma]a	\[Nu]$	\[Omega]min
	Average$	coef\[Sigma]2	eigV$	Ind	lcor$	L\[Sigma]3$	M$	out$	Spectra3dots	y	\[CapitalDelta]	\[CapitalSigma]1	
	Av$	coef\[Sigma]2$	eig$	Ind$	lmean	L$	n	P	Spe\[Sigma]1	y$	\[CapitalDelta]1	\[CapitalSigma]1$	
	A$	coef\[Sigma]3	eme	i$	lmean0	m	na	P1	Spe\[Sigma]1$	\[Alpha]	\[CapitalDelta]2	\[CapitalSigma]2	
	broad	coef\[Sigma]3$	emeB	j	lmean0$	M	na$	P2	Spe\[Sigma]2	\[Alpha]a	\[CapitalDelta]3	\[CapitalSigma]2$	
	broad$	coef$	emeB$	j$	lmean$	M1	nmax	P3	Spe\[Sigma]2$	\[Alpha]a$	\[Delta]\[Omega]	\[CapitalSigma]3	
	c	Corr	eme$	Ka	Lora	M1$	nn	Pa	Spe\[Sigma]3	\[Alpha]\[Sigma]1	\[Mu]	\[CapitalSigma]3$	
	case	CorrSpec	ene	Ka$	Lora$	M2	nn$	re	Spe\[Sigma]3$	\[Alpha]\[Sigma]1$	\[Mu]\[Mu]	\[Omega]	
	Change	CorrSpec$	ene$	K\[Sigma]1	Lor\[Sigma]1	M2$	nt	regmat	Tota	\[Alpha]\[Sigma]2	\[Mu]\[Mu]\[Mu]	\[Omega]1	
	ChangeBack	Corr$	f1	K\[Sigma]1$	Lor\[Sigma]1$	Me	n\[Sigma]1	RegMat3dots	Tota$	\[Alpha]\[Sigma]2$	\[Mu]\[Mu]\[Mu]$	
	ChangeBack$	Co$	f1$	K\[Sigma]2	ls	Me$	n\[Sigma]1$	RegMatrix	Tot\[Sigma]1	\[Alpha]\[Sigma]3	\[Mu]\[Mu]$	\[Omega]2	
	Change$	c$	fs	K\[Sigma]2$	ls$	mm	n\[Sigma]2	RegMatrix$	Tot\[Sigma]1$	\[Alpha]\[Sigma]3$	\[Mu]$	\[Omega]2$	
	Co	Disa	g1	K\[Sigma]3	l\[CapitalDelta]1	mm$	n\[Sigma]2$	regmat$	x	\[Alpha]$	\[Nu]	\[Omega]3	

After running the first instance of the module:

	In[32]:= MemoryInUse[]
	Out[32]= 26536288

After running the second instance:

        In[35]:= MemoryInUse[]
        Out[35]= 32878688

Etc., the memory will keep increasing, although each module runs a
separate case and could be computed in separate notebooks, thus the
amount of required memory should be the same.

The variables indeed keep cluttering things from the various instances
of the module:

	A	coef\[Sigma]1	eig$	i$	lcor$	m	n	P3	Spe\[Sigma]1	\[Alpha]a$	\[Mu]\[Mu]\[Mu]	\[Omega]1$632
	AllM	coef\[Sigma]1$	eme	i$646	lcor$646	M	na	Pa	Spe\[Sigma]1$	\[Alpha]\[Sigma]1	\[Mu]\[Mu]\[Mu]$	\[Omega]1$647
	AllM$	coef\[Sigma]2	emeB	j	lmean	M1	na$	re	Spe\[Sigma]2	\[Alpha]\[Sigma]1$	\[Mu]\[Mu]$	\[Omega]1$648
	Av	coef\[Sigma]2$	emeB$	j$	lmean0	M1$	nmax	regmat	Spe\[Sigma]2$	\[Alpha]\[Sigma]2	\[Mu]$	\[Omega]2
	Average	coef\[Sigma]3	eme$	Ka	lmean0$	M2	nn	RegMat3dots	Spe\[Sigma]3	\[Alpha]\[Sigma]2$	\[Nu]	\[Omega]2$
	Average$	coef\[Sigma]3$	ene	Ka$	lmean$	M2$	nn$	RegMatrix	Spe\[Sigma]3$	\[Alpha]\[Sigma]3	\[Nu]\[Nu]	\[Omega]2$630
	Av$	coef$	ene$	Ka$629	Lora	Me	nt	RegMatrix$	Tota	\[Alpha]\[Sigma]3$	\[Nu]\[Nu]\[Nu]	\[Omega]2$632
	A$	Corr	f1	Ka$646	Lora$	Me$	n\[Sigma]1	RegMatrix$630	Tota$	\[Alpha]$	\[Nu]\[Nu]\[Nu]$	\[Omega]2$647
	broad	CorrSpec	f1$	K\[Sigma]1	Lor\[Sigma]1	mm	n\[Sigma]1$	RegMatrix$632	Tot\[Sigma]1	\[Gamma]	\[Nu]\[Nu]$	
	broad$	CorrSpec$	fs	K\[Sigma]1$	Lor\[Sigma]1$	mm$	n\[Sigma]2	RegMatrix$647	Tot\[Sigma]1$	\[Gamma]1	\[Nu]$	
	c	Corr$	g1	K\[Sigma]2	ls	mybasis	n\[Sigma]2$	RegMatrix$648	x	\[Gamma]2	\[CapitalSigma]1	\[Omega]3$
	case	Co$	g2	K\[Sigma]2$	ls$	mybasis$	n\[Sigma]3	regmat$	X	\[Gamma]3	\[CapitalSigma]1$	\[Omega]a
	Change	c$	g3	K\[Sigma]3	l\[CapitalDelta]1	myvar	n\[Sigma]3$	re$	Xsol	\[Gamma]a	\[CapitalSigma]2	\[Omega]a$
	ChangeBack	Disa	i	K\[Sigma]3$	L\[Sigma]1	m\[CapitalDelta]	n$	re$629	Xsol$	\[CapitalDelta]	\[CapitalSigma]2$	\[Omega]a$630
	ChangeBack$	Disa$	im	L	L\[Sigma]1$	m$	order	re$646	x$	\[CapitalDelta]1	\[CapitalSigma]3	\[Omega]a$632
	Change$	Dis\[Sigma]1	im$	La	L\[Sigma]2	M$	out	solMean	X$	\[CapitalDelta]2	\[CapitalSigma]3$	\[Omega]a$647
	Co	Dis\[Sigma]1$	im$629	La$	L\[Sigma]2$	M$630	out$	solMean$	y	\[CapitalDelta]3	\[Omega]	\[Omega]a$648
	coef	eig	im$646	La$629	L\[Sigma]3	M$632	P	Spea	y$	\[Delta]\[Omega]	\[Omega]1	\[Omega]max
	coefa	eigV	Ind	La$646	L\[Sigma]3$	M$647	P1	Spea$	\[Alpha]	\[Mu]	\[Omega]1$	\[Omega]min
	coefa$	eigV$	Ind$	lcor	L$	M$648	P2	Spectra3dots	\[Alpha]a	\[Mu]\[Mu]	\[Omega]1$630	

Now, if we take for instance, RegMatrix$632, which appears in the list above. It seems to take no memory:

     	In[39]:= ByteCount[RegMatrix$632]
	Out[39]= 0

But it clearly is stored in memory:

(a lot of more stuff here), and if I remove it:

	In[47]:= MemoryInUse[]
	Out[47]= 32879624
	In[48]:= Remove[RegMatrix$632]

	In[49]:= MemoryInUse[]
	Out[49]= 29521760

So clearly, along with all the other stuff lying around, it accounts
for this filling up of the memory. It seems there is a problem with
garbage collection and disposing of local variables defined within a

I don't think there is anything special with the module itself. It
calls other modules defined externally. At the same time the problem
does not seem reproducible defining a toy-module and looking for the
same behaviour. Does this problem seem familiar? Strange? What could
be causing it?

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