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diff --git a/docs/environment_variables.md b/docs/environment_variables.md new file mode 100644 index 00000000..4eb09659 --- /dev/null +++ b/docs/environment_variables.md @@ -0,0 +1,55 @@ +# Introduction + +For test purposes, environment variables can be set to control libyuv behavior. These should only be used for testing, to narrow down bugs or to test performance. + +# CPU + +By default the cpu is detected and the most advanced form of SIMD is used. But you can disable instruction sets selectively, or completely, falling back on C code. Set the variable to 1 to disable the specified instruction set. + +## All CPUs + LIBYUV_DISABLE_ASM + +## Intel CPUs + LIBYUV_DISABLE_X86 + LIBYUV_DISABLE_SSE2 + LIBYUV_DISABLE_SSSE3 + LIBYUV_DISABLE_SSE41 + LIBYUV_DISABLE_SSE42 + LIBYUV_DISABLE_AVX + LIBYUV_DISABLE_AVX2 + LIBYUV_DISABLE_ERMS + LIBYUV_DISABLE_FMA3 + LIBYUV_DISABLE_F16C + LIBYUV_DISABLE_AVX512BW + LIBYUV_DISABLE_AVX512VL + LIBYUV_DISABLE_AVX512VNNI + LIBYUV_DISABLE_AVX512VBMI + LIBYUV_DISABLE_AVX512VBMI2 + LIBYUV_DISABLE_AVX512VBITALG + LIBYUV_DISABLE_AVX512VPOPCNTDQ + LIBYUV_DISABLE_GFNI + +## ARM CPUs + + LIBYUV_DISABLE_NEON + +## MIPS CPUs + LIBYUV_DISABLE_MSA + +## LOONGARCH CPUs + LIBYUV_DISABLE_LSX + LIBYUV_DISABLE_LASX + +## RISCV CPUs + LIBYUV_DISABLE_RVV + +# Test Width/Height/Repeat + +The unittests default to a small image (128x72) to run fast. This can be set by environment variable to test a specific resolutions. +You can also repeat the test a specified number of iterations, allowing benchmarking and profiling. + + set LIBYUV_WIDTH=1280 + set LIBYUV_HEIGHT=720 + set LIBYUV_REPEAT=999 + set LIBYUV_FLAGS=-1 + set LIBYUV_CPU_INFO=-1 |