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Hi,

We are using MKL calls dgetrf & dgetrs from MKL 11.2 Update 2 to solve linear systems of small size (typically 4 X 4 or 9 X 9 or 16 X 16). Here is how the program works - we need to perform computations with systems of different sizes. We allocate memory, compute, free and repeat as required. Eventually, after several allocate-compute-free cycles, when we free the dynamically allocated array 'a' in the documentation at

https://software.intel.com/en-us/node/520892#642A8C07-088C-408D-BC89-D0F2A6E75416

we find that the program crashes with the error 'corrupted double-linked list' which suggests that 'ipiv' is over-writing/changing the malloc information for 'a'.

When we avoid the dgetrf & dgetrs calls by using an alternative function (that does not require solving the system), we find that the code executes correctly and exits normally.

Furthermore, we have determined that allocating 'ipiv' to be of size 1 larger than suggested by the documentation at

https://software.intel.com/en-us/node/520877#E4779E02-346C-4670-92AB-C67BD8559051

fixes the bug i.e. we do not see the 'corrupted double-linked list' error anymore and the program exits normally. Can you please confirm if the documentation is in error?

We are happy to supply our codebase along with a makefile to help resolve the problem.

Vishal Kasliwal & Michael Royster

Department of Physics, Drexel University

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The information that you have given is not sufficient to reproduce the problem. Here is a modified version of the DGETRS example distributed with MKL. It allocates, solves and deallocates the matrix, R.H.S. and IPIV arrays for a 4 X 4 matrix with NRHS=2, using the data provided with MKL for the DGETRS example. It does the allocate-factorize-solve-deallocate cycle 10,000 times. There were no errors (with the Windows version of MKL).

Program xdgetrs Integer nin, nout Parameter (nin=5, nout=6) Integer nmax, lda, nrhmax, ldb Parameter (nmax=8, lda=nmax, nrhmax=nmax, ldb=nmax) Character trans Parameter (trans='N') Integer i, ifail, info, j, n, nrhs Double Precision, Allocatable :: a(:, :), b(:, :) Double Precision as(lda, nmax), bs(ldb, nrhmax) Integer, Allocatable :: ipiv(:) Double Precision pert(2) Integer astat External dgetrf, dgetrs ! Write (nout, *) 'DGETRS Example Program Results' Read (nin, *) Read (nin, *) n, nrhs If (n<=nmax .And. nrhs<=nrhmax) Then Read (nin, *)((as(i,j),j=1,n), i=1, n) Read (nin, *)((bs(i,j),j=1,nrhs), i=1, n) Do kiter = 1, 10000 Allocate (a(n,n), b(n,nrhs), ipiv(n), Stat=astat) If (astat/=0) Stop 'Error allocating A, B and IPIV' Call random_number(pert) a(1:n, 1:n) = as(1:n, 1:n)*(1D0+0.01*pert(1)) !perturb b(1:n, 1:nrhs) = bs(1:n, 1:nrhs)*(1D0+0.01*pert(2)) Call dgetrf(n, n, a, n, ipiv, info) ! If (info==0) Then Call dgetrs(trans, n, nrhs, a, n, ipiv, b, n, info) ifail = 0 If (mod(kiter,1000)==0) Write (*, '(1x,i5,2x,2ES12.4)') & kiter, (sum(b(:,i)), i=1, nrhs) Else Write (nout, *) 'The matrix factorization failed' End If Deallocate (a, b, ipiv) End Do End If Stop ! End Program xdgetrs

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