reduce for kqmax_new_j is unnecessary #1032
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… 199,this reduce can be omit
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I think I left this in when I at some point refactored the code; I would suggest you just remove the call to warp_reduce_max without a comment why it's not there since it shouldn't be there in the first place. Also fattn-vec-f32.cuh has the same issue, please remove the corresponding line there too while you're at it.
src/ggml-cuda/fattn-vec-f16.cuh
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| @@ -220,7 +220,8 @@ static __global__ void flash_attn_vec_ext_f16( | |||
| for (int j = 0; j < ncols; ++j) { | |||
| half kqmax_new_j = ncols == 1 ? kqmax_new : kqmax_new_arr[j]; | |||
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| kqmax_new_j = warp_reduce_max(kqmax_new_j); | |||
| /* kqmax_new_j in every thread within warp is same after operate at line 199,this reduce can be omit */ | |||
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Strictly speaking it is not exactly the same since the order in which you sum up floating point values makes a difference for the result but this is negligible. And there is no reason why the maximum value in particular should be preferred.
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fattn-vec-f32.cuh and fattn-vec-f16.cuh is updated. |
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using this patch,the performance will increase about 1%-2% ,testing in A800
test-backend-ops -o FLASH_ATTN_EXT -b CUDA0 perf
i am do some trick to letting nb=1,2,3,7 will using flash_attn_vec_ext_f16(because A800 is capable for wmma) just for the eval performance
origin:
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 90112 runs - 11.51 us/run - 4.19 MFLOP/run - 364.41 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 73728 runs - 14.38 us/run - 8.39 MFLOP/run - 583.51 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 21.18 us/run - 12.58 MFLOP/run - 594.02 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 30654 runs - 34.17 us/run - 29.36 MFLOP/run - 859.30 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 57344 runs - 19.03 us/run - 8.39 MFLOP/run - 440.74 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 41727 runs - 25.04 us/run - 16.78 MFLOP/run - 670.07 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 27818 runs - 36.84 us/run - 25.17 MFLOP/run - 683.06 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 15327 runs - 67.79 us/run - 58.72 MFLOP/run - 866.21 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 81920 runs - 12.68 us/run - 4.19 MFLOP/run - 330.79 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 65536 runs - 16.16 us/run - 8.39 MFLOP/run - 519.10 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 22.11 us/run - 12.58 MFLOP/run - 569.02 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 27248 runs - 37.08 us/run - 29.36 MFLOP/run - 791.89 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 65536 runs - 16.47 us/run - 8.39 MFLOP/run - 509.47 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 21.93 us/run - 16.78 MFLOP/run - 765.03 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 31792 runs - 35.48 us/run - 25.17 MFLOP/run - 709.22 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 17030 runs - 60.34 us/run - 58.72 MFLOP/run - 973.20 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 90112 runs - 11.23 us/run - 4.19 MFLOP/run - 373.53 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 73728 runs - 13.85 us/run - 8.39 MFLOP/run - 605.60 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 55636 runs - 20.40 us/run - 12.58 MFLOP/run - 616.89 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 27248 runs - 40.79 us/run - 29.36 MFLOP/run - 719.80 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 57344 runs - 18.64 us/run - 8.39 MFLOP/run - 450.01 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 23.73 us/run - 16.78 MFLOP/run - 707.06 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 31792 runs - 34.49 us/run - 25.17 MFLOP/run - 729.75 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 15327 runs - 66.55 us/run - 58.72 MFLOP/run - 882.32 GFLOPS
apply this patch:
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 90112 runs - 11.14 us/run - 4.19 MFLOP/run - 376.67 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 73728 runs - 14.02 us/run - 8.39 MFLOP/run - 598.41 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 55636 runs - 20.66 us/run - 12.58 MFLOP/run - 609.01 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 30654 runs - 33.68 us/run - 29.36 MFLOP/run - 871.69 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 57344 runs - 18.82 us/run - 8.39 MFLOP/run - 445.67 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 41727 runs - 24.57 us/run - 16.78 MFLOP/run - 682.88 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 27818 runs - 36.41 us/run - 25.17 MFLOP/run - 691.19 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=1,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 15327 runs - 66.20 us/run - 58.72 MFLOP/run - 887.06 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 81920 runs - 12.70 us/run - 4.19 MFLOP/run - 330.27 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 65536 runs - 15.85 us/run - 8.39 MFLOP/run - 529.23 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 21.69 us/run - 12.58 MFLOP/run - 580.05 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 27248 runs - 36.73 us/run - 29.36 MFLOP/run - 799.45 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 65536 runs - 16.19 us/run - 8.39 MFLOP/run - 518.10 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 21.47 us/run - 16.78 MFLOP/run - 781.60 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 31792 runs - 34.47 us/run - 25.17 MFLOP/run - 730.00 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=1,max_bias=8.000000,logit_softcap=0.000000,type_KV=f16): 17030 runs - 59.55 us/run - 58.72 MFLOP/run - 986.15 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=1,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 98304 runs - 10.93 us/run - 4.19 MFLOP/run - 383.64 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=2,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 81920 runs - 13.52 us/run - 8.39 MFLOP/run - 620.46 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=3,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 55636 runs - 19.85 us/run - 12.58 MFLOP/run - 633.98 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=512,nb=7,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 27248 runs - 40.10 us/run - 29.36 MFLOP/run - 732.12 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=1,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 57344 runs - 18.36 us/run - 8.39 MFLOP/run - 456.96 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=2,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 47688 runs - 23.40 us/run - 16.78 MFLOP/run - 716.87 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=3,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 31792 runs - 33.66 us/run - 25.17 MFLOP/run - 747.69 GFLOPS
FLASH_ATTN_EXT(hs=64,nh=32,kv=1024,nb=7,mask=0,max_bias=0.000000,logit_softcap=0.000000,type_KV=f16): 15327 runs - 65.55 us/run - 58.72 MFLOP/run - 895.82 GFLOPS