       Slow Show/Graphics in v6.0

• To: mathgroup at smc.vnet.net
• Subject: [mg80906] Slow Show/Graphics in v6.0
• From: Alex Shvydky <ashv at lle.rochester.edu>
• Date: Wed, 5 Sep 2007 02:53:32 -0400 (EDT)
• Organization: University of Rochester

```Hello,

Just wanted to share my puzzlement (utter disappointment/
frastration) with a ridiculously slow speed of Show/Graphics
routines in the v6.0 of Mathematica as compared to 5.2,
which to me at this point makes v6.0 plain unusable.

Working with hydrodynamic simulations I need to
visualize the computational grid. So I wrote
simple Mathematica routines to draw a simulation grid.
In 5.2 they worked fabulously for the past couple of
years.

Here's an example.
First, set up two 2dimensional x- and y-coordinate
arrays.

Timing[
mr = 350;
mt = 350;
xar = Table[((ir - 1.)/(mr - 1.))*Cos[Pi*((it - 1.)/(mt - 1.))],
{it, 1, mt}, {ir, 1, mr}];
yar = Table[((ir - 1.)/(mr - 1.))*Sin[Pi*((it - 1.)/(mt - 1.))],
{it, 1, mt}, {ir, 1, mr}];
]

In v6.0 it took
Out= {2.312, Null}
In v5.2 it took
{0.281 Second, Null}

Which is an order of magnitude difference, but hold on.
Now let's plot the mesh by simply constructing table
of edges of all the cells (I am aware that the algorithm
below is very unoptimized and can be made faster etc. etc.
It was not my intention to discuss here what should be the
fastest algorithm to plot a 2-d mesh,
nor was it my intention to debate the issue why one
would need to plot such a large mesh in the first place...,
but rather to compare the execution time for an IDENTICAL
code on v6.0 and v5.2. and get some confirmation/explanation
of such a suspiciously slow execution speed!).:

Timing[
Show[
Graphics[{Hue[0.7], AbsoluteThickness[0.1],
Table[{Line[{{xar[[it,ir]], yar[[it,ir]]},
{xar[[it,ir + 1]],yar[[it,ir + 1]]},
{xar[[it + 1,ir + 1]], yar[[it + 1,ir + 1]]},
{xar[[it + 1,ir]], yar[[it + 1,ir]]}}]},
{ir, 1, mr - 1}, {it, 1, mt - 1}]
}],
PlotRange -> {{-1, 1}, {0, 1}}, AspectRatio -> 1/2, Axes -> True,
DisplayFunction -> \$DisplayFunction, ImageSize -> 800]]

While the timing as, it is returned by the Timing[] function,
is smaller in the v6.0:
{1.703, <Here goes the actual graphics>}
vs.
{2.094 Second, -Graphics-}
in v5.2

The actual cell evaluation time in v.6.0 is 124.11 seconds
vs. 2.22 seconds in v 5.2. ???!!!!!!!

if someone from Wolfram Research would explain if
that is intended (unavoidable) by design or maybe
a simple setting (which I am unaware of) or a future patch
will be able to fix it.

Also, it is horribly slow to resize the above graphics
in v5.2 you just grab the corned and drag. In v6.0 you
must do it 10-100 times slower (is it possible
that I just have a very poor graphics card?).

Thanks,
Alex Shvydky

```

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