Mma 1.2 memory management bug (not in 2.0)

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Mma 1.2 memory management bug (not in 2.0)*From*: Pekka Janhunen <pjanhune at finsun.csc.fi>*Date*: Mon, 21 Oct 91 09:46:18 +0200

Consider the following: Mathematica (sun4) 1.2 (June 13, 1990) [With pre-loaded data] by S. Wolfram, D. Grayson, R. Maeder, H. Cejtin, S. Omohundro, D. Ballman and J. Keiper with I. Rivin and D. Withoff Copyright 1988,1989,1990 Wolfram Research Inc. -- Terminal graphics initialized -- In[1]:= A=Table[Random[],{10},{10}]; In[2]:= Do[Inverse[A]; Print[MemoryInUse[]],{5}] 1410600 1411456 1412312 1413168 1414024 It appears to be that Inverse in Mathematica (1.2) leaves one internal copy of the matrix hanging in memory, never freeing it. No user command, Clear, ClearAll, Remove etc. can return the memory, to my experience. Similarly behave also LinearSolve and Eigenvalues. This bug appears only if the matrices are numerical (floating point). Functions Det and SingularValues, on the other hand, behave correctly! This provides a way out of the dilemma, at least for the Inverse case, namely we can also find the matrix if we first calculate its singular value decomposition: In[3]:= inverse[A_]:=\ Block[{u,w,v},{u,w,v}=SingularValues[A]; \ Conjugate[Transpose[v]].DiagonalMatrix[1/w].u] In[4]:= Do[inverse[A]; Print[MemoryInUse[]],{5}] 1419832 1419832 1419832 1419832 1419832 Now the memory does not grow a single byte. We do not yet (...) have 2.0, so if someone out there could check this with the new version. This bug was noticed when one program, after running for 24 hours on a Sun SPARC, ended up using 32 megabytes virtual memory. When the substitution Inverse->inverse was made, the memory remained under 6 megabytes. The increment of memory when Inverse is used is very nearly equal to the floating point (C language) internal representation of the matrix. Pekka Janhunen Finnish Meteorological Institute Geophysics Department email: pjanhune at finsun.csc.fi P.S. Steve Christensen pointed out that the bug does NOT exist on Mma 2.0. The memory does not grow, whether one uses Inverse or SingularValues. Thanks for S.C. for providing this information.