New submission from deekay <dee2theka...@gmail.com>:
I'm baffled by the performance difference of the following two semantically
equivalent(?) programs.
Python:
#test.py
import time
starttime=time.time()
import tensorflow
print(f"Import took: {time.time() - starttime}")
vs C using CPython
//test.c
#include <Python.h>
#include <stdio.h>
#include <time.h>
int main(int argc, char *argv[])
{
Py_Initialize();
clock_t t = clock();
PyObject* pModule = PyImport_ImportModule("tensorflow");
double time_taken = ((double)clock() - t)/CLOCKS_PER_SEC;
printf("Import took: %f\n", time_taken);
return 0;
}
Now compare the two:
cl.exe /I"C:\Program Files\Python37\include" test.c
link test.obj python37.lib /LIBPATH:"C:\Program Files\Python37\libs"
.\test.exe
> 2020-04-17 13:00:51.598550: W
> tensorflow/stream_executor/platform/default/dso_loader.cc:55] Could not load
> dynamic library 'cudart64_100.dll'; dlerror: cudart64_100.dll not found
> 2020-04-17 13:00:51.606296: I
> tensorflow/stream_executor/cuda/cudart_stub.cc:29] Ignore above cudart
> dlerror if you do not have a GPU set up on your machine.
> **Import took: 23.160523891448975**
python test.py
> 2020-04-17 13:01:19.525648: W
> tensorflow/stream_executor/platform/default/dso_loader.cc:55] Could not load
> dynamic library 'cudart64_100.dll'; dlerror: cudart64_100.dll not found
> 2020-04-17 13:01:19.530726: I
> tensorflow/stream_executor/cuda/cudart_stub.cc:29] Ignore above cudart
> dlerror if you do not have a GPU set up on your machine.
> **Import took: 2.3172824382781982**
Not that it should matter much but my tensorflow version is 1.15
Why is the python VM code so much faster than the compiled CPython code?
Does the python vm add some magic that PyImport_ImportModule doesn't?
----------
components: C API
messages: 366683
nosy: deekay
priority: normal
severity: normal
status: open
title: python code order of magnitude faster than equivalent CPython code for
simple import statement
versions: Python 3.7
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue40314>
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