Compiled functions

• To: mathgroup at smc.vnet.net
• Subject: [mg4594] Compiled functions
• From: Stefan Schulz <sschulz at chemie.fu-berlin.de>
• Date: Wed, 21 Aug 1996 03:25:16 -0400
• Sender: owner-wri-mathgroup at wolfram.com

Dear Mathematica users,

is it possible to compile a mathematica expression that uses
vectors of real numbers as input? Since in my application I need
to solve a symmetric tridiagonal linear system which is diagonally
dominate quite often I am thinking about defining
a compiled function that could look something like

SymmTridiagonalSolve = Compile[{{a, _List}, {b, _List}, {r, _List}},
Module[{ n        = Length[r],
solution = Array[0, Length[r]],
aux1     = Array[0, Length[r]],
aux,
a1       = Prepend[a, 0],
i
},
aux = 1/b[[1]];
solution[[1]] = r[[1]] aux;
Do[{
aux1[[i]] = a1[[i]] aux,
aux = 1/(b[[i]]-a1[[i]] aux1[[i]]),
solution[[i]] = (r[[i]]-a1[[i]] solution[[i-1]]) aux
},
{i, 2, n}];
Do[{
solution[[i]] -= aux1[[i+1]] solution[[i+1]]
},
{i, n-1, 1, -1}];
solution
]
]

Since according to the Mathematica book, the only types that can be
specified for compilation are _Integer, _Real, _Complex, and True | False
I know that this construct does not work, but
has somebody perhaps come up with a clever workaround
to make it possible to also pass vectors as arguments?

Many thanks in advance.

Regards,

Stefan

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