QMKL6

QMKL6 (VideoCore VI QPU Math Kernel Library) is a BLAS library that runs on VideoCore VI QPU, the GPU (Graphic Processing Unit) of Raspberry Pi 4. QMKL6 implements the same C interfaces (e.g. cblas_sgemm) as the other BLAS libraries, so you can change your program to use QMKL6 only by modifying compiler flags.

Requirements

QMKL6 currently only supports Raspberry Pi 4 because it is the only Raspberry Pi board equipped with VideoCore VI QPU. If you need QPU-accelerated BLAS functions on older Raspberry Pi boards, use QMKL instead.

We recommend to use the official Raspberry Pi OS (formerly called Raspbian) distribution. However, QMKL6 does not work correctly with the current 5.4.y kernel because the patchset for internal API changes is not merged yet (see raspberrypi/linux#3816). For that reason, you need to check your kernel version by running uname -r. If it shows 5.4.y or higher, you need to downgrade the kernel to 4.19.y (no workaround exists for aarch64):

$ uname -r
5.4.51-v7l+
$ wget http://archive.raspberrypi.org/debian/pool/main/r/raspberrypi-firmware/raspberrypi-kernel_1.20200601-1_armhf.deb
$ sudo dpkg -i raspberrypi-kernel_1.20200601-1_armhf.deb
$ sudo reboot

To build and run QMKL6, you need to install py-videocore6 and libdrm_v3d in advance.

QMKL6 communicates with the QPU through /dev/dri/card0, which is exposed by the V3D DRM kernel driver. To access the device, you need to belong to the video group by running sudo usermod --append --groups video $USER (re-login to take effect).

Running tests

$ sudo apt update
$ sudo apt install build-essential git cmake
$ git clone https://github.com/Idein/qmkl6
$ cd qmkl6/
$ cmake .
$ make
$ ctest -V

Installation

$ make package
$ sudo dpkg -i qmkl6-0.0.0-Linux.deb

After that, you can obtain the compiler flags by running pkg-config --cflags --libs blas-qmkl6.