.. _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

.. note:: The tbbmalloc library in oneTBB is fully binary compatible with TBB.