I would definitely use complex precision. All direct sovler packages support complex, superlu, mumps and petsc.
Hong On Sat, Dec 10, 2011 at 10:03 AM, Jack Poulson <jack.poulson at gmail.com> wrote: > Xiangdong, > > Nearly all of the time in a serial sparse-direct factorization goes into > performing many different dense "frontal" factorizations. Efficient > implementations of dense LU factorization spend almost all of their time > within dense matrix-matrix multiplication, and complex matrix-matrix > multiplication requires about 4 times as much work as real matrix-matrix > multiplication, as half the work is in adds and half the work is in > multiplies with the standard approach (complex addition and multiplication > are respectively require 2 and 6 real flops). > > Overall, a complex sparse-direct solve takes about 4 times as many flops > (and twice as much memory) as a real sparse-direct solve, but due to having > a higher arithmetic intensity (roughly, more flops per piece of data), the > complex version will almost always take significantly less than 4 times as > long as the real version. > > Jack > > > On Fri, Dec 9, 2011 at 11:54 PM, Xiangdong Liang <xdliang at gmail.com> wrote: >> >> Hello everyone, >> >> I am solving a complex linear system C x = d, where C= A+ iB (A, B are >> real), in sparse-direct solver. So far, I use the real formulation by >> solving the linear system [A, -B; B,A]. ?The reason we chose this >> approach is to use the property of that the imaginary part B in our >> problem is sparser than A. However, I just found that the spare-direct >> solver cannot benefit from this property. >> >> Now, I am thinking to re-implement it in to complex version by solving >> Cx=d in the complex version. Of course, complex formulation would >> perform better for iterative solvers since it only has half >> eigenvalues than the corresponding real formulations. I am wondering >> the comparison between real and complex formulation for sparse-direct >> solver. Can anyone share experiences on this? Thanks. >> >> Xiangdong > >