[Visualpython-users] Possible memory leak

[Jason M. <jas...@vp...>]

Hi,

I am using visual python to graph a lot of data in real time (I tried with
matplotlib but it's just too slow).

Anyway, it works incredibly well (thanks for a great little library by the
way - it's not exactly publicised just how fast and easy to use it is!!).

I have live data on 15 separate windows, all being updated at 125 times per
second!!

However, there is a problem.  After about ten minutes I get MemoryError from
numpy.

The code works by using one curve per display entity.  Each curve has 300
x/y points.  The y points in every graph are updated each frame, the x
points are unchanged (0..299).

The error comes from the line of code that shifts the data along as it adds
new data (I've tried various methods, including manual iteration, list
splices and numpy.roll) but all have the same memory effect.  I first tried
the old 3.x VPython and got the same results from Numeric under Python 2.5.
I upgraded to Python 2.7 with latest numpy and the latest VPython and got
the same result.

<code>
for c in curves:
  n=curves.index(c)
  b=np.roll(c.y,-1)
  b[-1]=new_value[n]
  c.y=b
</code>

The MemoryError is always at one of the last three lines or within numpy's
libraries.
I've tried c.get_y() and c.set_y() with the same results.

I've checked all my other buffers in the rest of the code and non are
getting larger, nor is c.y or the temporary variable, b in the example
above.

My conculusion is that this can only be something to do with the internal
workings of either numpy (and Numeric) or VPython.

I tried the following in IDLE:

<code>
import numpy as np
count=0
a=np.arange(10)
while True:
	count=count+1
	b=np.roll(a,-1)
	b[-1]=count
	a=b
</code>

And let this run for several minutes (42+ million cycles) without a crash.

So, what am I doing wrong (or is there a memory bug in VPython)?

Cheers,
Jason.