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Re: Fast copy of buffer data into a matrix

From: John W. Eaton
Subject: Re: Fast copy of buffer data into a matrix
Date: Fri, 9 Feb 2007 12:55:30 -0500

On  9-Feb-2007, John Swensen wrote:

| Is there a difference between:
| 1) static unit8NDArray m (dim_vector(settings.width, settings.height));
| and
| 2) static uint8NDArray m = octave_value(m1).uint8_array_value();
| ?

Yes.  Is m1 a Matrix object?  Assuming it is, then the first statement
creates a uint8NDArray object directly and the second takes m1 (double
values if it is a Matrix object), wraps it in an octave_value object,
then extracts a uint8NDArray object from it, requiring a type
conversion and data copying.  So the second is a lot more work and
wastes space if all you really want is a uint8NDArray object.


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