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vec: optimize AVX2/FMA sum-of-squares with loop unrolling and FMA #17642

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@GermanAizek GermanAizek commented Dec 1, 2025 •
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This simply change has greatly affected vec_dot_q, and in my tests it floats strongly, sometimes 2-3-4 times almost higher, and sometimes a 2-3 times worse.

image

Full Benchmark

devuan@devuan:~/GIT/llama.cpp/cmake-build-release/bin$ ./test-quantize-perf > opt.txt
devuan@devuan:~/GIT/llama.cpp/cmake-build-release/bin$ ./test-quantize-perf > master.txt
devuan@devuan:~/GIT/llama.cpp/cmake-build-release/bin$ diff -u master.txt opt.txt | colordiff
--- master.txt  2025-12-01 12:14:36.491798486 +0300
+++ opt.txt     2025-12-01 12:13:58.491799972 +0300
@@ -1,107 +1,107 @@
 f16
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    294.47
-      avg cycles/32 vals   :    319.96
-      float32 throughput   :      0.85 GB/s
-      quantized throughput :      0.43 GB/s
+      min cycles/32 vals   :    188.25
+      avg cycles/32 vals   :    188.48
+      float32 throughput   :      1.44 GB/s
+      quantized throughput :      0.72 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      4.67
-      avg cycles/32 vals   :     12.89
-      float32 throughput   :      8.03 GB/s
-      quantized throughput :      4.02 GB/s
+      min cycles/32 vals   :      4.55
+      avg cycles/32 vals   :     25.29
+      float32 throughput   :     10.17 GB/s
+      quantized throughput :      5.09 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     85.10
-      avg cycles/32 vals   :     86.52
-      float32 throughput   :      3.11 GB/s
-      quantized throughput :      1.56 GB/s
+      min cycles/32 vals   :     84.80
+      avg cycles/32 vals   :     85.95
+      float32 throughput   :      3.18 GB/s
+      quantized throughput :      1.59 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :      4.55
-      avg cycles/32 vals   :      4.70
+      min cycles/32 vals   :      4.54
+      avg cycles/32 vals   :      4.67
       float32 throughput   :     50.86 GB/s
       quantized throughput :     25.43 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
       min cycles/32 vals   :      5.30
-      avg cycles/32 vals   :      5.40
-      float32 throughput   :     50.86 GB/s
-      quantized throughput :     25.43 GB/s
+      avg cycles/32 vals   :      5.38
+      float32 throughput   :     38.15 GB/s
+      quantized throughput :     19.07 GB/s
 
 q4_0
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    128.62
-      avg cycles/32 vals   :    128.80
+      min cycles/32 vals   :    128.58
+      avg cycles/32 vals   :    128.76
       float32 throughput   :      2.12 GB/s
       quantized throughput :      0.30 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    128.67
-      avg cycles/32 vals   :    128.78
+      min cycles/32 vals   :    128.66
+      avg cycles/32 vals   :    128.79
       float32 throughput   :      2.12 GB/s
       quantized throughput :      0.30 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     15.22
+      min cycles/32 vals   :     15.20
       avg cycles/32 vals   :     15.32
       float32 throughput   :     16.95 GB/s
       quantized throughput :      2.38 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     29.12
-      avg cycles/32 vals   :     29.27
+      min cycles/32 vals   :     29.11
+      avg cycles/32 vals   :     29.33
       float32 throughput   :      8.98 GB/s
       quantized throughput :      1.26 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      4.52
-      avg cycles/32 vals   :      4.72
+      min cycles/32 vals   :      4.54
+      avg cycles/32 vals   :      4.67
       float32 throughput   :     50.86 GB/s
       quantized throughput :      7.15 GB/s
 
 q4_1
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    109.82
-      avg cycles/32 vals   :    109.99
+      min cycles/32 vals   :    110.03
+      avg cycles/32 vals   :    110.14
       float32 throughput   :      2.46 GB/s
       quantized throughput :      0.38 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    109.97
-      avg cycles/32 vals   :    110.22
+      min cycles/32 vals   :    110.03
+      avg cycles/32 vals   :    110.16
       float32 throughput   :      2.46 GB/s
       quantized throughput :      0.38 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     16.70
-      avg cycles/32 vals   :     17.95
-      float32 throughput   :     15.26 GB/s
-      quantized throughput :      2.38 GB/s
+      min cycles/32 vals   :     16.71
+      avg cycles/32 vals   :     18.11
+      float32 throughput   :     13.87 GB/s
+      quantized throughput :      2.17 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     51.41
-      avg cycles/32 vals   :     51.86
+      min cycles/32 vals   :     51.55
+      avg cycles/32 vals   :     51.92
       float32 throughput   :      5.09 GB/s
       quantized throughput :      0.79 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      4.69
+      min cycles/32 vals   :      4.67
       avg cycles/32 vals   :      4.80
       float32 throughput   :     50.86 GB/s
       quantized throughput :      7.95 GB/s
@@ -109,103 +109,103 @@
 q5_0
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    240.55
-      avg cycles/32 vals   :    240.88
+      min cycles/32 vals   :    240.52
+      avg cycles/32 vals   :    240.76
       float32 throughput   :      1.13 GB/s
       quantized throughput :      0.19 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    240.45
-      avg cycles/32 vals   :    240.78
+      min cycles/32 vals   :    240.65
+      avg cycles/32 vals   :    240.89
       float32 throughput   :      1.13 GB/s
       quantized throughput :      0.19 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     96.15
-      avg cycles/32 vals   :     96.28
+      min cycles/32 vals   :     96.21
+      avg cycles/32 vals   :     96.32
       float32 throughput   :      2.83 GB/s
       quantized throughput :      0.49 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
       min cycles/32 vals   :     29.11
-      avg cycles/32 vals   :     29.27
-      float32 throughput   :      8.98 GB/s
-      quantized throughput :      1.54 GB/s
+      avg cycles/32 vals   :     29.30
+      float32 throughput   :     10.17 GB/s
+      quantized throughput :      1.75 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      6.12
-      avg cycles/32 vals   :      6.27
-      float32 throughput   :     38.15 GB/s
-      quantized throughput :      6.56 GB/s
+      min cycles/32 vals   :      6.14
+      avg cycles/32 vals   :      6.21
+      float32 throughput   :     50.86 GB/s
+      quantized throughput :      8.74 GB/s
 
 q5_1
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    205.94
-      avg cycles/32 vals   :    206.23
-      float32 throughput   :      1.32 GB/s
+      min cycles/32 vals   :    205.76
+      avg cycles/32 vals   :    206.57
+      float32 throughput   :      1.33 GB/s
       quantized throughput :      0.25 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    206.43
-      avg cycles/32 vals   :    206.90
+      min cycles/32 vals   :    206.59
+      avg cycles/32 vals   :    206.78
       float32 throughput   :      1.32 GB/s
       quantized throughput :      0.25 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     99.19
-      avg cycles/32 vals   :     99.37
+      min cycles/32 vals   :     98.55
+      avg cycles/32 vals   :     98.70
       float32 throughput   :      2.72 GB/s
       quantized throughput :      0.51 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     51.09
-      avg cycles/32 vals   :     51.68
-      float32 throughput   :      5.26 GB/s
-      quantized throughput :      0.99 GB/s
+      min cycles/32 vals   :     51.59
+      avg cycles/32 vals   :     52.24
+      float32 throughput   :      5.09 GB/s
+      quantized throughput :      0.95 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      6.03
-      avg cycles/32 vals   :      6.09
+      min cycles/32 vals   :      6.02
+      avg cycles/32 vals   :      6.20
       float32 throughput   :     38.15 GB/s
       quantized throughput :      7.15 GB/s
 
 q8_0
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    303.78
-      avg cycles/32 vals   :    304.45
-      float32 throughput   :      0.90 GB/s
+      min cycles/32 vals   :    303.77
+      avg cycles/32 vals   :    304.66
+      float32 throughput   :      0.89 GB/s
       quantized throughput :      0.24 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     29.29
-      avg cycles/32 vals   :     29.34
-      float32 throughput   :      9.54 GB/s
-      quantized throughput :      2.53 GB/s
+      min cycles/32 vals   :     29.27
+      avg cycles/32 vals   :     29.39
+      float32 throughput   :      8.98 GB/s
+      quantized throughput :      2.38 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     14.29
-      avg cycles/32 vals   :     14.37
+      min cycles/32 vals   :     14.24
+      avg cycles/32 vals   :     14.32
       float32 throughput   :     16.95 GB/s
       quantized throughput :      4.50 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     29.14
-      avg cycles/32 vals   :     29.30
-      float32 throughput   :      9.54 GB/s
-      quantized throughput :      2.53 GB/s
+      min cycles/32 vals   :     29.11
+      avg cycles/32 vals   :     29.36
+      float32 throughput   :      8.98 GB/s
+      quantized throughput :      2.38 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
@@ -217,396 +217,396 @@
 q2_K
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :   4242.51
-      avg cycles/32 vals   :   4257.87
+      min cycles/32 vals   :   4241.52
+      avg cycles/32 vals   :   4291.42
       float32 throughput   :      0.06 GB/s
       quantized throughput :      0.01 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :   4240.97
-      avg cycles/32 vals   :   4320.46
+      min cycles/32 vals   :   4239.26
+      avg cycles/32 vals   :   4364.00
       float32 throughput   :      0.06 GB/s
       quantized throughput :      0.01 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
       min cycles/32 vals   :     80.86
-      avg cycles/32 vals   :     80.97
+      avg cycles/32 vals   :     81.07
       float32 throughput   :      3.32 GB/s
       quantized throughput :      0.27 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.68
-      avg cycles/32 vals   :    127.06
+      min cycles/32 vals   :    126.38
+      avg cycles/32 vals   :    126.94
       float32 throughput   :      2.15 GB/s
       quantized throughput :      0.18 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      2.70
-      avg cycles/32 vals   :      2.85
-      float32 throughput   :     76.29 GB/s
-      quantized throughput :      6.26 GB/s
+      min cycles/32 vals   :      8.34
+      avg cycles/32 vals   :      8.63
+      float32 throughput   :     25.43 GB/s
+      quantized throughput :      2.09 GB/s
 
 q3_K
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    463.23
-      avg cycles/32 vals   :    465.04
-      float32 throughput   :      0.59 GB/s
+      min cycles/32 vals   :    464.61
+      avg cycles/32 vals   :    466.17
+      float32 throughput   :      0.58 GB/s
       quantized throughput :      0.06 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    463.86
-      avg cycles/32 vals   :    464.66
+      min cycles/32 vals   :    464.12
+      avg cycles/32 vals   :    465.35
       float32 throughput   :      0.59 GB/s
       quantized throughput :      0.06 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     23.77
-      avg cycles/32 vals   :     23.91
+      min cycles/32 vals   :     23.75
+      avg cycles/32 vals   :     23.86
       float32 throughput   :     11.74 GB/s
       quantized throughput :      1.26 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.68
+      min cycles/32 vals   :    126.65
       avg cycles/32 vals   :    126.96
-      float32 throughput   :      2.18 GB/s
+      float32 throughput   :      2.15 GB/s
       quantized throughput :      0.23 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      8.07
+      min cycles/32 vals   :      7.97
       avg cycles/32 vals   :      8.13
-      float32 throughput   :     30.52 GB/s
-      quantized throughput :      3.28 GB/s
+      float32 throughput   :     76.29 GB/s
+      quantized throughput :      8.20 GB/s
 
 q4_K
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :   5065.16
-      avg cycles/32 vals   :   5100.72
+      min cycles/32 vals   :   5060.34
+      avg cycles/32 vals   :   5105.36
       float32 throughput   :      0.05 GB/s
       quantized throughput :      0.01 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :   5065.95
-      avg cycles/32 vals   :   5067.42
+      min cycles/32 vals   :   5058.95
+      avg cycles/32 vals   :   5071.13
       float32 throughput   :      0.05 GB/s
       quantized throughput :      0.01 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     15.34
-      avg cycles/32 vals   :     15.45
+      min cycles/32 vals   :     15.32
+      avg cycles/32 vals   :     15.41
       float32 throughput   :     16.95 GB/s
       quantized throughput :      2.38 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.81
-      avg cycles/32 vals   :    127.04
+      min cycles/32 vals   :    126.63
+      avg cycles/32 vals   :    127.05
       float32 throughput   :      2.15 GB/s
       quantized throughput :      0.30 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      4.13
-      avg cycles/32 vals   :     25.95
-      float32 throughput   :     10.17 GB/s
-      quantized throughput :      1.43 GB/s
+      min cycles/32 vals   :      4.30
+      avg cycles/32 vals   :     24.27
+      float32 throughput   :     10.90 GB/s
+      quantized throughput :      1.53 GB/s
 
 q5_K
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :   3977.85
-      avg cycles/32 vals   :   3989.26
+      min cycles/32 vals   :   3974.84
+      avg cycles/32 vals   :   4029.74
       float32 throughput   :      0.07 GB/s
       quantized throughput :      0.01 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :   3979.48
-      avg cycles/32 vals   :   4016.21
+      min cycles/32 vals   :   3972.98
+      avg cycles/32 vals   :   4145.78
       float32 throughput   :      0.07 GB/s
       quantized throughput :      0.01 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     20.53
-      avg cycles/32 vals   :     20.78
+      min cycles/32 vals   :     20.66
+      avg cycles/32 vals   :     20.86
       float32 throughput   :     12.72 GB/s
       quantized throughput :      2.19 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.57
-      avg cycles/32 vals   :    185.54
-      float32 throughput   :      1.47 GB/s
-      quantized throughput :      0.25 GB/s
+      min cycles/32 vals   :    126.77
+      avg cycles/32 vals   :    127.22
+      float32 throughput   :      2.18 GB/s
+      quantized throughput :      0.37 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      7.17
-      avg cycles/32 vals   :     26.32
+      min cycles/32 vals   :      7.12
+      avg cycles/32 vals   :     26.74
       float32 throughput   :     10.17 GB/s
       quantized throughput :      1.75 GB/s
 
 q6_K
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :   2758.61
-      avg cycles/32 vals   :   2784.79
+      min cycles/32 vals   :   2762.16
+      avg cycles/32 vals   :   2792.98
       float32 throughput   :      0.10 GB/s
       quantized throughput :      0.02 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :   2763.22
-      avg cycles/32 vals   :   2774.24
+      min cycles/32 vals   :   2763.62
+      avg cycles/32 vals   :   2799.36
       float32 throughput   :      0.10 GB/s
       quantized throughput :      0.02 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    103.45
-      avg cycles/32 vals   :    103.57
-      float32 throughput   :      2.63 GB/s
-      quantized throughput :      0.54 GB/s
+      min cycles/32 vals   :    103.27
+      avg cycles/32 vals   :    103.51
+      float32 throughput   :      2.59 GB/s
+      quantized throughput :      0.53 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.73
-      avg cycles/32 vals   :    126.87
+      min cycles/32 vals   :    126.66
+      avg cycles/32 vals   :    127.07
       float32 throughput   :      2.15 GB/s
       quantized throughput :      0.44 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      7.79
-      avg cycles/32 vals   :     27.25
-      float32 throughput   :     10.17 GB/s
-      quantized throughput :      2.09 GB/s
+      min cycles/32 vals   :      7.74
+      avg cycles/32 vals   :      7.93
+      float32 throughput   :     38.15 GB/s
+      quantized throughput :      7.82 GB/s
 
 iq4_nl
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :   1559.49
-      avg cycles/32 vals   :   1579.94
+      min cycles/32 vals   :   1566.73
+      avg cycles/32 vals   :   1568.58
       float32 throughput   :      0.17 GB/s
       quantized throughput :      0.02 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :   1559.31
-      avg cycles/32 vals   :   1569.49
-      float32 throughput   :      0.17 GB/s
+      min cycles/32 vals   :   1566.66
+      avg cycles/32 vals   :   1704.78
+      float32 throughput   :      0.16 GB/s
       quantized throughput :      0.02 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    114.20
-      avg cycles/32 vals   :    114.29
+      min cycles/32 vals   :    114.15
+      avg cycles/32 vals   :    114.23
       float32 throughput   :      2.38 GB/s
       quantized throughput :      0.34 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     29.24
-      avg cycles/32 vals   :     29.32
-      float32 throughput   :      8.98 GB/s
-      quantized throughput :      1.26 GB/s
+      min cycles/32 vals   :     29.11
+      avg cycles/32 vals   :     29.30
+      float32 throughput   :      9.54 GB/s
+      quantized throughput :      1.34 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
       min cycles/32 vals   :      4.90
-      avg cycles/32 vals   :      4.99
-      float32 throughput   :     50.86 GB/s
-      quantized throughput :      7.15 GB/s
+      avg cycles/32 vals   :      5.00
+      float32 throughput   :     76.29 GB/s
+      quantized throughput :     10.73 GB/s
 
 iq4_xs
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :  23011.23
-      avg cycles/32 vals   :  23112.32
+      min cycles/32 vals   :  23020.66
+      avg cycles/32 vals   :  23417.59
       float32 throughput   :      0.01 GB/s
       quantized throughput :      0.00 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :  22991.27
-      avg cycles/32 vals   :  23075.28
+      min cycles/32 vals   :  23020.19
+      avg cycles/32 vals   :  23368.66
       float32 throughput   :      0.01 GB/s
       quantized throughput :      0.00 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     87.52
-      avg cycles/32 vals   :     87.80
-      float32 throughput   :      3.11 GB/s
+      min cycles/32 vals   :     87.66
+      avg cycles/32 vals   :     87.82
+      float32 throughput   :      3.05 GB/s
       quantized throughput :      0.41 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.62
-      avg cycles/32 vals   :    126.98
-      float32 throughput   :      2.15 GB/s
-      quantized throughput :      0.29 GB/s
+      min cycles/32 vals   :    126.68
+      avg cycles/32 vals   :    127.04
+      float32 throughput   :      2.12 GB/s
+      quantized throughput :      0.28 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
       min cycles/32 vals   :      9.73
-      avg cycles/32 vals   :      9.81
+      avg cycles/32 vals   :      9.79
       float32 throughput   :     25.43 GB/s
       quantized throughput :      3.38 GB/s
 
 bf16
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :     38.62
-      avg cycles/32 vals   :     38.65
-      float32 throughput   :      6.94 GB/s
-      quantized throughput :      3.47 GB/s
+      min cycles/32 vals   :     38.68
+      avg cycles/32 vals   :     38.74
+      float32 throughput   :      7.27 GB/s
+      quantized throughput :      3.63 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     20.81
-      avg cycles/32 vals   :     20.91
+      min cycles/32 vals   :     20.88
+      avg cycles/32 vals   :     20.98
       float32 throughput   :     12.72 GB/s
       quantized throughput :      6.36 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      7.09
-      avg cycles/32 vals   :      7.19
+      min cycles/32 vals   :      7.10
+      avg cycles/32 vals   :      7.22
       float32 throughput   :     38.15 GB/s
       quantized throughput :     19.07 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     20.81
-      avg cycles/32 vals   :     20.93
+      min cycles/32 vals   :     20.88
+      avg cycles/32 vals   :     21.04
       float32 throughput   :     12.72 GB/s
       quantized throughput :      6.36 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
       min cycles/32 vals   :      5.30
-      avg cycles/32 vals   :      5.37
-      float32 throughput   :     76.29 GB/s
-      quantized throughput :     38.15 GB/s
+      avg cycles/32 vals   :      5.46
+      float32 throughput   :     38.15 GB/s
+      quantized throughput :     19.07 GB/s
 
 tq1_0
   quantize_row_q_reference
     4096 values (0.02 MB)
       min cycles/32 vals   :    262.05
-      avg cycles/32 vals   :    262.32
+      avg cycles/32 vals   :    262.42
       float32 throughput   :      1.04 GB/s
       quantized throughput :      0.05 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    262.02
-      avg cycles/32 vals   :    262.33
-      float32 throughput   :      1.04 GB/s
-      quantized throughput :      0.05 GB/s
+      min cycles/32 vals   :    262.05
+      avg cycles/32 vals   :    262.40
+      float32 throughput   :      1.05 GB/s
+      quantized throughput :      0.06 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     18.09
-      avg cycles/32 vals   :     18.29
+      min cycles/32 vals   :     17.98
+      avg cycles/32 vals   :     18.31
       float32 throughput   :     15.26 GB/s
       quantized throughput :      0.80 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.68
-      avg cycles/32 vals   :    126.96
-      float32 throughput   :      2.18 GB/s
+      min cycles/32 vals   :    126.83
+      avg cycles/32 vals   :    126.98
+      float32 throughput   :      2.15 GB/s
       quantized throughput :      0.11 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      3.35
-      avg cycles/32 vals   :      3.43
+      min cycles/32 vals   :      3.30
+      avg cycles/32 vals   :      3.41
       float32 throughput   :     76.29 GB/s
       quantized throughput :      4.02 GB/s
 
 tq2_0
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    264.61
-      avg cycles/32 vals   :    265.22
-      float32 throughput   :      1.04 GB/s
+      min cycles/32 vals   :    264.71
+      avg cycles/32 vals   :    265.10
+      float32 throughput   :      1.02 GB/s
       quantized throughput :      0.07 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    264.83
-      avg cycles/32 vals   :    265.20
-      float32 throughput   :      1.02 GB/s
+      min cycles/32 vals   :    264.58
+      avg cycles/32 vals   :    265.10
+      float32 throughput   :      1.04 GB/s
       quantized throughput :      0.07 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     13.64
-      avg cycles/32 vals   :     13.89
+      min cycles/32 vals   :     13.66
+      avg cycles/32 vals   :     13.87
       float32 throughput   :     19.07 GB/s
       quantized throughput :      1.23 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :    126.66
-      avg cycles/32 vals   :    126.84
-      float32 throughput   :      2.15 GB/s
+      min cycles/32 vals   :    126.86
+      avg cycles/32 vals   :    127.12
+      float32 throughput   :      2.18 GB/s
       quantized throughput :      0.14 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      1.60
-      avg cycles/32 vals   :      1.72
+      min cycles/32 vals   :      1.56
+      avg cycles/32 vals   :      1.71
       float32 throughput   :     76.29 GB/s
       quantized throughput :      4.92 GB/s
 
 mxfp4
   quantize_row_q_reference
     4096 values (0.02 MB)
-      min cycles/32 vals   :    702.07
-      avg cycles/32 vals   :    702.59
+      min cycles/32 vals   :    701.70
+      avg cycles/32 vals   :    702.39
       float32 throughput   :      0.39 GB/s
       quantized throughput :      0.05 GB/s
 
   quantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :    702.22
-      avg cycles/32 vals   :    721.19
+      min cycles/32 vals   :    701.59
+      avg cycles/32 vals   :    720.28
       float32 throughput   :      0.38 GB/s
       quantized throughput :      0.05 GB/s
 
   dequantize_row_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :     94.14
-      avg cycles/32 vals   :     94.28
+      min cycles/32 vals   :     94.19
+      avg cycles/32 vals   :     94.39
       float32 throughput   :      2.88 GB/s
       quantized throughput :      0.38 GB/s
 
   quantize_row_q_dot
     4096 values (0.02 MB)
-      min cycles/32 vals   :     29.06
-      avg cycles/32 vals   :     29.27
-      float32 throughput   :     10.90 GB/s
-      quantized throughput :      1.45 GB/s
+      min cycles/32 vals   :     29.04
+      avg cycles/32 vals   :     29.31
+      float32 throughput   :      9.54 GB/s
+      quantized throughput :      1.27 GB/s
 
   vec_dot_q
     4096 values (0.02 MB)
-      min cycles/32 vals   :      6.05
-      avg cycles/32 vals   :      6.15
+      min cycles/32 vals   :      6.09
+      avg cycles/32 vals   :      6.18
       float32 throughput   :     38.15 GB/s
       quantized throughput :      5.07 GB/s

Description

  • Loop Unrolling: The loop step is increased from 8 to 32 elements, reducing loop overhead and exposing more instruction-level parallelism.
  • Parallel Accumulators: Instead of accumulating into a single scalar sum, four __m256 vector registers are used to accumulate partial sums in parallel. This breaks the dependency chain on a single accumulator, allowing for better pipeline utilization.
  • Fused Multiply-Add (FMA): The _mm256_fmadd_ps intrinsic is explicitly used for val * val + sum_vec, combining the multiplication and addition into a single instruction, which can improve both throughput and numerical precision.
  • Broadcast mean once: The mean value is broadcast to a __m256 vector once outside the loop (mean_vec), avoiding repeated broadcasts within the loop.
  • Post-loop Reduction: The final horizontal sum of the four parallel accumulators is performed efficiently after the main loop.

References:

  1. Intel - Fast Parallel Reductions with SIMD Instructions:

  2. Intel - Fused Multiply-Add (FMA) Instructions:

  3. Wikipedia - Loop Unrolling:

Co-Authored-By: Gemini 2.5 Pro (References and description commit changes)

@GermanAizek
vec: optimize AVX2/FMA sum-of-squares with loop unrolling and paralle…
b73b2d9 
…l FMA

-   **Loop Unrolling:** The loop step is increased from 8 to 32 elements, reducing loop overhead and exposing more instruction-level parallelism.
-   **Parallel Accumulators:** Instead of accumulating into a single scalar sum, four `__m256` vector registers are used to accumulate partial sums in parallel. This breaks the dependency chain on a single accumulator, allowing for better pipeline utilization.
-   **Fused Multiply-Add (FMA):** The `_mm256_fmadd_ps` intrinsic is explicitly used for `val * val + sum_vec`, combining the multiplication and addition into a single instruction, which can improve both throughput and numerical precision.
-   **Broadcast `mean` once:** The `mean` value is broadcast to a `__m256` vector once outside the loop (`mean_vec`), avoiding repeated broadcasts within the loop.
-   **Post-loop Reduction:** The final horizontal sum of the four parallel accumulators is performed efficiently after the main loop.

References:
1.  **Intel - Fast Parallel Reductions with SIMD Instructions:**
    *   Explains the concept of using multiple accumulators for parallel reduction, directly relevant to this optimization.
    *   Link: [https://software.intel.com/content/www/us/en/develop/articles/fast-parallel-reductions-with-simd-instructions.html](https://software.intel.com/content/www/us/en/develop/articles/fast-parallel-reductions-with-simd-instructions.html)

2.  **Intel - Fused Multiply-Add (FMA) Instructions:**
    *   Details the benefits and usage of FMA instructions for improved performance and precision.
    *   Link: [https://software.intel.com/content/www/us/en/develop/articles/fused-multiply-add-fma-instructions.html](https://software.intel.com/content/www/us/en/develop/articles/fused-multiply-add-fma-instructions.html)

3.  **Wikipedia - Loop Unrolling:**
    *   A general explanation of loop unrolling, a fundamental optimization technique used here.
    *   Link: [https://en.wikipedia.org/wiki/Loop_unrolling](https://en.wikipedia.org/wiki/Loop_unrolling)
@loci-dev loci-dev mentioned this pull request Dec 1, 2025
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@GermanAizek GermanAizek changed the title vec: optimize AVX2/FMA sum-of-squares with loop unrolling vec: optimize AVX2/FMA sum-of-squares with loop unrolling and FMA Dec 1, 2025
@github-actions github-actions bot added the ggml changes relating to the ggml tensor library for machine learning label Dec 1, 2025
@pwilkin pwilkin added the vibe-coded Created with heavy use of LLM assistants, requires human verification label Dec 1, 2025
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