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MathGroup Archive 2007

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Re: problem with DumpSaving SparseArrays in 6.0

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75717] Re: [mg75656] problem with DumpSaving SparseArrays in 6.0
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Wed, 9 May 2007 04:29:14 -0400 (EDT)
  • References: <5896993.1178622176403.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

Here's a slightly more complete demonstration:

b = a = SparseArray[{2, 3} -> 7, {5, 5}];
DumpSave["test.mx", b];

<< "test.mx"
a == b

True

Dimensions /@ {a, b}

{{5, 5}, {}}

a & b are equal, but they don't have the same dimensions!!

Not only that, but if you highlight and copy the output cell text:

b

\!\(\*
TagBox[
RowBox[{"SparseArray", "[",
RowBox[{"Automatic", ",",
RowBox[{"{",
RowBox[{"5", ",", "5"}], "}"}], ",", "0", ",",
RowBox[{"{",
RowBox[{"1", ",",
RowBox[{"{",
RowBox[{
RowBox[{"{",
RowBox[{"0", ",", "0", ",", "1", ",", "1", ",", "1", ",", "1"}],
           "}"}], ",",
RowBox[{"{",
RowBox[{"{", "3", "}"}], "}"}]}], "}"}], ",",
RowBox[{"{", "7", "}"}]}], "}"}]}], "]"}],
False,
Editable->False]\)

and paste it in a new cell,

SparseArray[Automatic, {5,
   5}, 0, {1, {{0, 0, 1, 1, 1, 1}, {{3}}}, {7}}]
Dimensions[%]

\!\(\*
TagBox[
RowBox[{"SparseArray", "[",
RowBox[{
InterpretationBox[
RowBox[{"\<\"<\"\>", "", "1", "", "\<\">\"\>"}],
SequenceForm["<", 1, ">"],
Editable->False], ",",
RowBox[{"{",
RowBox[{"5", ",", "5"}], "}"}]}], "]"}],
False,
Editable->False]\)

{5, 5}

NOW you have the correct matrix.

Bizarro.

Bobby

On Tue, 08 May 2007 04:46:01 -0500, Roman <rschmied at gmail.com> wrote:

> Hello all,
> There seems to be a problem with DumpSave and SparseArray in 6.0. If
> you DumpSave a simple SparseArray like this:
>
>    A = SparseArray[{2, 3} -> 7, {5, 5}];
>    DumpSave["test.mx", A];
>
> then read it back:
>
> << "test.mx"
> A
>
> you get the following output:
>    SparseArray[Automatic, {5, 5}, 0, {1, {{0, 0, 1, 1, 1, 1}, {{3}}},
> {7}}]
>
> While this is correct in principle, in practice A is now no longer
> usable. Try, for example,
>    MatrixForm[A]
> This will complain, just like any other use of A as a matrix will.
>
> Do you have any idea for a workaround, to convert A back into a usable=

> matrix?
>
> Thanks!
> Roman.
>
>
>



-- =

DrMajorBob at bigfoot.com


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