Increased performance and buffer preallocation for Writer and WKTWriter

[meastp]

This patch adds the ability to preallocate the buffer of Writer, and also removes an unnecessary intermediate string object in WKTWriter, resulting in increased performance. A test case for separate Writer objects have been added to the test suite. All tests pass successfully.

From the mailing list:

Fra: geos-devel-bounces@lists.osgeo.org [mailto:geos-devel-
bounces@lists.osgeo.org] På vegne av Mats Taraldsvik
Sendt: 18. januar 2013 12:53
Til: geos-devel@lists.osgeo.org
Emne: [geos-devel] Ability to preallocate the WKT stringstream
buffer for really large geometries?

Hi,

Generally, I'm very satisfied with the WKTWriter, which is really
easy to use, and converts the Geometries to the WKT format. However,
when converting large geometries (in this case, contour lines), I
get a major decrease in performance.

By looking at the source code (and profiling), I believe the use of
a stringstream and hence a dynamically increasing string buffer,
constantly reallocating, is causing the performance penalty.
Possibly also copying the large string.

Is there anything I can do to improve this scenario? Do you accept
contributions to fix this (e.g. passing in the expected size of the
resulting WKT string)?

Regards

On Fri, Feb 08, 2013 at 07:22:21AM +0000, Mats Taraldsvik wrote:

Have you considered this issue? Do you accept patches to solve this by
changing the interface (considering GEOS is a port of JTS and follows
it closely)? :)

I'll be glad to review and apply any patch speeding up WKT writing.
I'm fine with providing an enhanced interface for 3.4.x series, as long as the old one remains for backward API compatibility.

If you start with that please consider taking a look at
http://trac.osgeo.org/geos/ticket/355 and
http://trac.osgeo.org/geos/ticket/310

Please also make sure the testsuite covers enough cases.

Thank you !

--strk;

Regards

Mats Taraldsvik

[strk]

I've committed the appendCoordinate optimization in both 3.3 branch and trunk.
As for the Writer changes, can you please start a new testcase for it rather than reusing WKTWriter testcase ?
Also please don't mix formatting and functional changes.

I'm closing this, expecting next pull. Thanks !