Slow LinearSolve.

• To: mathgroup at smc.vnet.net
• Subject: [mg49657] Slow LinearSolve.
• From: Aaron Fude <aaronfude at yahoo.com>
• Date: Mon, 26 Jul 2004 04:28:54 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

``` Hi,

Within 24 hours and counting, Mathematica was not able to solve Ax = b for
the following A and the following B. Another system does this in a matter of seconds.
How do make Mathematica do the same? I use "LinearSolve[A, b]"

A = {{1, -I, -1, I, 1, -I, -1, I, 1, -I, -1, I, 1}, {1, E^(((-5*I)/12)*Pi),
E^(((-5*I)/6)*Pi),
E^(((3*I)/4)*Pi), E^((I/3)*Pi), E^((-I/12)*Pi), -I, E^(((-11*I)/12)*Pi),
E^(((2*I)/3)*Pi),
E^((I/4)*Pi), E^((-I/6)*Pi), E^(((-7*I)/12)*Pi), -1},
{1, E^((-I/3)*Pi), E^(((-2*I)/3)*Pi), -1, E^(((2*I)/3)*Pi), E^((I/3)*Pi), 1,
E^((-I/3)*Pi),
E^(((-2*I)/3)*Pi), -1, E^(((2*I)/3)*Pi), E^((I/3)*Pi), 1},
{1, E^((-I/4)*Pi), -I, E^(((-3*I)/4)*Pi), -1, E^(((3*I)/4)*Pi), I,
E^((I/4)*Pi), 1,
E^((-I/4)*Pi), -I, E^(((-3*I)/4)*Pi), -1}, {1, E^((-I/6)*Pi),
E^((-I/3)*Pi), -I,
E^(((-2*I)/3)*Pi), E^(((-5*I)/6)*Pi), -1, E^(((5*I)/6)*Pi),
E^(((2*I)/3)*Pi), I,
E^((I/3)*Pi), E^((I/6)*Pi), 1}, {1, E^((-I/12)*Pi), E^((-I/6)*Pi),
E^((-I/4)*Pi),
E^((-I/3)*Pi), E^(((-5*I)/12)*Pi), -I, E^(((-7*I)/12)*Pi),
E^(((-2*I)/3)*Pi),
E^(((-3*I)/4)*Pi), E^(((-5*I)/6)*Pi), E^(((-11*I)/12)*Pi), -1},
{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, E^((I/12)*Pi), E^((I/6)*Pi),
E^((I/4)*Pi),
E^((I/3)*Pi), E^(((5*I)/12)*Pi), I, E^(((7*I)/12)*Pi), E^(((2*I)/3)*Pi),
E^(((3*I)/4)*Pi),
E^(((5*I)/6)*Pi), E^(((11*I)/12)*Pi), -1}, {1, E^((I/6)*Pi), E^((I/3)*Pi),
I,
E^(((2*I)/3)*Pi), E^(((5*I)/6)*Pi), -1, E^(((-5*I)/6)*Pi),
E^(((-2*I)/3)*Pi), -I,
E^((-I/3)*Pi), E^((-I/6)*Pi), 1}, {1, E^((I/4)*Pi), I, E^(((3*I)/4)*Pi), -1,
E^(((-3*I)/4)*Pi), -I, E^((-I/4)*Pi), 1, E^((I/4)*Pi), I,
E^(((3*I)/4)*Pi), -1},
{1, E^((I/3)*Pi), E^(((2*I)/3)*Pi), -1, E^(((-2*I)/3)*Pi), E^((-I/3)*Pi), 1,
E^((I/3)*Pi),
E^(((2*I)/3)*Pi), -1, E^(((-2*I)/3)*Pi), E^((-I/3)*Pi), 1},
{1, E^(((5*I)/12)*Pi), E^(((5*I)/6)*Pi), E^(((-3*I)/4)*Pi), E^((-I/3)*Pi),
E^((I/12)*Pi), I,
E^(((11*I)/12)*Pi), E^(((-2*I)/3)*Pi), E^((-I/4)*Pi), E^((I/6)*Pi),
E^(((7*I)/12)*Pi), -1},
{1, I, -1, -I, 1, I, -1, -I, 1, I, -1, -I, 1}}

b = {0, (-2*I)/5, 0, (-2*I)/3, 0, -2*I, Pi, 2*I, 0, (2*I)/3, 0, (2*I)/5, 0}

```

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