CPU features
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Compiler CPU flags
customize the TensorFlow source build to take advantage of the availability of some CPU features that contribute to a speedier execution of TensorFlow code
Available CPU flags on target system can be found with following command and Linux kernel source helps unravel the meaning for each flag
$ cat /proc/cpuinfo | grep flags
...
flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate sme ssbd mba sev ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr wbnoinvd arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif umip rdpid overflow_recov succor smca
Optimization flags will be supplied when configuring the TensorFlow source build. The following command is used to populate the optimization flags:
$grep flags -m1 /proc/cpuinfo | cut -d ":" -f 2 | tr '[:upper:]' '[:lower:]' | { read FLAGS; OPT="-march=native"; for flag in $FLAGS; do case "$flag" in "sse4_1" | "sse4_2" | "ssse3" | "fma" | "cx16" | "popcnt" | "avx" | "avx2") OPT+=" -m$flag";; esac; done; MODOPT=${OPT//_/\.}; echo "$MODOPT"; }
and followings are an output example on AMD EPYC Process
-march=native -mssse3 -mfma -mcx16 -msse4.1 -msse4.2 -mpopcnt -mavx -mavx2
| No | Flag | CPU Feature | Additional Info |
|---|---|---|---|
| 1 | ssse3 | Supplemental Streaming SIMD Extensions 3 (SSSE-3) instruction set | |
| 2 | sse4_1 | Streaming SIMD Extensions 4.1 (SSE-4.1) instruction set | |
| 3 | sse4_2 | Streaming SIDM Extensions 4.2 (SSE-4.2) instruction set | |
| 4 | fma | Fused multiply-add (FMA) instruction set | |
| 5 | cx16 | CMPXCHG16B instruction (double-width compare-and-swap) | |
| 6 | popcnt | Population count instruction (count number of bits set to 1) | |
| 7 | avx | Advanced Vector Extensions | |
| 8 | avx2 | Advanced Vector Extension 2 |