How to disable openmp when using tesseract api?

[Xingtong Chen]

In tesseract document, I found that if I need to disable multithread, I need the configure option

../../configure --disable-openmp

This works well on my machine.

But I still cannot figure out how to disable multithread tesseract when using teseract api.

I have tried -DOPENMP_SIMD_FALSE, but this didn't work. Is there any compile flag to disable openmp?

I use g++ compiler with version "gcc version 12.2.0 (Debian 12.2.0-14)".

[Zdenko Podobny]

So you build the tesseract library without openmp, but when you use it (by calling api) multithreading is there?

Do I understand you correctly? How did you find it out?

Zdenko

st 18. 12. 2024 o 6:43 Xingtong Chen <chenxt...@gmail.com> napísal(a):

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[Xingtong Chen]

Apologize for my unclear expression. There are 2 tesseracts on my machine:

1. One is built from the github release (5.5.0). I use the  --disable-openmp  flag to conigure and I get a build without multithread.

2. I install libtesseract5 (5.3.0-2 amd64) from debian apt and the api head file is in my /usr/include folder. I compile a demo using g++ with version  “gcc version 12.2.0 (Debian 12.2.0-14)”.When I run the executable file, the process use 4 threads on my machine.

I find it by checking htop command results.

I just tried using OpenMP to perform multithreaded recognition operations with tesseract::TessBaseAPI* (using libtesseract5), but it seems the multithreading effect has disappeared.  That's weird to me.

Thank you for your patience ;)

[Zdenko Podobny]

You limit number of used threads by environment variable. E.g. set before running demo program this:

set OMP_NUM_THREADS=1

or use omp_set_num_threads[1] function within your program.

[1] https://gcc.gnu.org/onlinedocs/libgomp/omp_005fset_005fnum_005fthreads.html

Zdenko

st 18. 12. 2024 o 9:50 Xingtong Chen <chenxt...@gmail.com> napísal(a):

Apologize for my unclear expression. There are 2 tesseracts on my machine:

1. One is built from the github release (5.5.0). I use the  --disable-openmp  flag to conigure and I get a build without multithread.

2. I install libtesseract5 (5.3.0-2 amd64) from debian apt and the api head file is in my /usr/include folder. I compile a demo using g++ with version  “gcc version 12.2.0 (Debian 12.2.0-14)”.When I run the executable file, the process use 4 threads on my machine.

I find it by checking htop command results.

I just tried using OpenMP to perform multithreaded recognition operations with tesseract::TessBaseAPI* (using libtesseract5), but it seems the multithreading effect has disappeared.  That's weird to me.

Thank you for your patience ;)

在2024年12月17日星期二 UTC-8 22:43:21<zdenop> 写道：

To view this discussion visit https://groups.google.com/d/msgid/tesseract-ocr/acc5239c-cd91-4110-9825-479467105598n%40googlegroups.com.

[Xingtong Chen]

omp_set_num_threads(1) in demo main function doesn't seem to work, but I think using omp to multithread running tesseract works.

Thanks. ;)