.. _Mixing_Two_Runtimes:
Mixing two runtimes
=======================================
Threading Building Blocks (TBB) and oneAPI Threading Building Blocks (oneTBB) can be safely used in
the same application. TBB and oneTBB runtimes are named differently and can be loaded safely within
the same process. In addition, the ABI versioning is completely different that prevents symbols
conflicts.
However, if both runtimes are loaded into the same process it can lead to
oversubscription because each runtime will use its own pool of threads. It might lead to a
performance penalty due to increased number of context switches. To check if both TBB and
oneTBB are loaded to the application, export ``TBB_VERSION=1`` before the application run. If
both runtimes are loaded there will be two blocks of output, for example:
oneTBB possible output:
.. code:: text
oneTBB: SPECIFICATION VERSION 1.0
oneTBB: VERSION 2021.2
oneTBB: INTERFACE VERSION 12020
oneTBB: TBB_USE_DEBUG 1
oneTBB: TBB_USE_ASSERT 1
oneTBB: TOOLS SUPPORT disabled
TBB possible output:
.. code:: text
TBB: VERSION 2018.0
TBB: INTERFACE VERSION 10006
TBB: BUILD_DATE Mon 01 Mar 2021 01:28:40 PM UTC
TBB: BUILD_HOST localhost (x86_64)
TBB: BUILD_OS Fedora release 32 (Thirty Two)
TBB: BUILD_KERNEL Linux 5.8.9-200.fc32.x86_64 #1 SMP Mon Sep 14 18:28:45 UTC 2020
TBB: BUILD_GCC g++ (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9)
TBB: BUILD_LIBC 2.31
TBB: BUILD_LD GNU ld version 2.34-6.fc32
TBB: BUILD_TARGET intel64 on cc10_libc2.31_kernel5.8.9
TBB: BUILD_COMMAND g++ -DDO_ITT_NOTIFY -g -O2 -DUSE_PTHREAD -m64 -fPIC -D__TBB_BUILD=1 -Wall -Wno-parentheses -Wno-non-virtual-dtor -I../../src -I../../src/rml/include -I../../include -I.
TBB: TBB_USE_DEBUG 0
TBB: TBB_USE_ASSERT 0
TBB: DO_ITT_NOTIFY 1
TBB: RML private
TBB: Tools support disabled
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