iplot: long datablock stucks

[mzechmeister]

Passing a long datablock (~4000 lines) stucks

import gplot
iplot = gplot.Iplot(tmp='$')
iplot([1.000313517867877869656356345634865]*4000, ' w l')

while 3000 lines would be processed.

[mzechmeister]

With uri=False it works and the plot shows up

iplot = gplot.Iplot(tmp='$', uri=False)
iplot([1.000313517867877869656356345634865]*4000, ' w l')

So could be made to the default value.

[mzechmeister]

Here is the problem extracted and can be tested also in normal python shell:

import subprocess
import os

gp = subprocess.Popen('gnuplot ', shell=True, stdin=subprocess.PIPE,
         universal_newlines=True, bufsize=0)

os.system('rm -f tmp.png')
os.mkfifo('tmp.png')
print('''
set out "tmp.png"
$data1 <<EOD
''', file=gp.stdin)
print("\n".join(map(str,[1.000313517867877869656356345634865]*4000)), file=gp.stdin)

Again, this will stuck for 4000 lines (but run for 3000 lines).
The problem arises when gnuplot opens the created fifo with set out "tmp.png". If tmp.png does not exists, a normal file is created and it runs.

[mzechmeister]

According to
https://askubuntu.com/questions/439289/cat-to-named-pipe-causes-hang
http://kodedevil.com/2017/07/07/linux-fifos-python/
something is needed to read the fifo.

Indeed, inserting fifo = os.open('tmp.png', os.O_RDONLY) right after set output , the following works:

import subprocess
import os

gp = subprocess.Popen('gnuplot ', shell=True, stdin=subprocess.PIPE,
         universal_newlines=True, bufsize=0)

os.system('rm -f tmp.png')
os.mkfifo('tmp.png')

print('set out "tmp.png"', file=gp.stdin)
fifo = os.open('tmp.png', os.O_RDONLY)
print('$data1 <<EOD', file=gp.stdin)
print("\n".join(map(str,[1.000313517867877869656356345634865]*4000)), file=gp.stdin)