OV - attention-avx512 - Loop 52

	Loop Id: 52	Module: attention-avx512	Source: attention.cpp:27-33	Coverage: 0.32%

0x405050 LEA	(,%R11,8),%EDX

0x405058 VXORPS	%XMM7,%XMM7,%XMM7

0x40505c MOV	-0x40(%RBP),%R10D

0x405060 MOV	%R9D,%ESI

0x405063 MOV	-0x70(%RBP),%RDI

0x405067 VXORPS	%XMM8,%XMM8,%XMM8

0x40506c VXORPS	%XMM9,%XMM9,%XMM9

0x405071 VXORPS	%XMM10,%XMM10,%XMM10

0x405076 VXORPS	%XMM11,%XMM11,%XMM11

0x40507b VXORPS	%XMM12,%XMM12,%XMM12

0x405080 VXORPS	%XMM13,%XMM13,%XMM13

0x405085 VXORPS	%XMM14,%XMM14,%XMM14

0x40508a NOPW	(%RAX,%RAX,1)

  (51) 0x405090 MOV	%R10D,%R14D

  (51) 0x405093 VMOVSS	(%R15,%R14,4),%XMM15

  (51) 0x405099 VCVTSS2SD	%XMM15,%XMM15,%XMM15

  (51) 0x40509e LEA	-0x7(%RSI),%R14D

  (51) 0x4050a2 VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x4050aa VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x4050b0 VFMADD231SD	%XMM16,%XMM15,%XMM14

  (51) 0x4050b6 LEA	-0x6(%RSI),%R14D

  (51) 0x4050ba VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x4050c2 VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x4050c8 VFMADD231SD	%XMM16,%XMM15,%XMM13

  (51) 0x4050ce LEA	-0x5(%RSI),%R14D

  (51) 0x4050d2 VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x4050da VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x4050e0 LEA	-0x4(%RSI),%R14D

  (51) 0x4050e4 VMOVSS	(%R13,%R14,4),%XMM17

  (51) 0x4050ec VCVTSS2SD	%XMM17,%XMM17,%XMM17

  (51) 0x4050f2 VFMADD231SD	%XMM16,%XMM15,%XMM12

  (51) 0x4050f8 VFMADD231SD	%XMM17,%XMM15,%XMM11

  (51) 0x4050fe LEA	-0x3(%RSI),%R14D

  (51) 0x405102 VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x40510a VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x405110 VFMADD231SD	%XMM16,%XMM15,%XMM10

  (51) 0x405116 LEA	-0x2(%RSI),%R14D

  (51) 0x40511a VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x405122 VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x405128 VFMADD231SD	%XMM16,%XMM15,%XMM9

  (51) 0x40512e LEA	-0x1(%RSI),%R14D

  (51) 0x405132 VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x40513a VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x405140 VFMADD231SD	%XMM16,%XMM15,%XMM8

  (51) 0x405146 MOV	%ESI,%R14D

  (51) 0x405149 VMOVSS	(%R13,%R14,4),%XMM16

  (51) 0x405151 VCVTSS2SD	%XMM16,%XMM16,%XMM16

  (51) 0x405157 VFMADD231SD	%XMM16,%XMM15,%XMM7

  (51) 0x40515d ADD	%R8D,%ESI

  (51) 0x405160 INC	%R10D

  (51) 0x405163 DEC	%RDI

  (51) 0x405166 JNE	405090

0x40516c VCVTSD2SS	%XMM14,%XMM14,%XMM14

0x405171 LEA	(%RAX,%RDX,1),%ESI

0x405174 VMOVSS	%XMM14,(%RBX,%RSI,4)

0x405179 VCVTSD2SS	%XMM13,%XMM13,%XMM13

0x40517e LEA	0x1(%RAX,%RDX,1),%ESI

0x405182 VMOVSS	%XMM13,(%RBX,%RSI,4)

0x405187 VCVTSD2SS	%XMM12,%XMM12,%XMM12

0x40518c LEA	0x2(%RAX,%RDX,1),%ESI

0x405190 VMOVSS	%XMM12,(%RBX,%RSI,4)

0x405195 VCVTSD2SS	%XMM11,%XMM11,%XMM11

0x40519a LEA	0x3(%RAX,%RDX,1),%ESI

0x40519e VMOVSS	%XMM11,(%RBX,%RSI,4)

0x4051a3 VCVTSD2SS	%XMM10,%XMM10,%XMM10

0x4051a8 LEA	0x4(%RAX,%RDX,1),%ESI

0x4051ac VMOVSS	%XMM10,(%RBX,%RSI,4)

0x4051b1 VCVTSD2SS	%XMM9,%XMM9,%XMM9

0x4051b6 LEA	0x5(%RAX,%RDX,1),%ESI

0x4051ba VMOVSS	%XMM9,(%RBX,%RSI,4)

0x4051bf VCVTSD2SS	%XMM8,%XMM8,%XMM8

0x4051c4 LEA	0x6(%RAX,%RDX,1),%ESI

0x4051c8 VMOVSS	%XMM8,(%RBX,%RSI,4)

0x4051cd VCVTSD2SS	%XMM7,%XMM7,%XMM7

0x4051d1 LEA	0x7(%RAX,%RDX,1),%EDX

0x4051d5 VMOVSS	%XMM7,(%RBX,%RDX,4)

0x4051da ADD	$0x8,%R9D

0x4051de CMP	-0x60(%RBP),%R11

0x4051e2 LEA	0x1(%R11),%R11

0x4051e6 JNE	405050

/home/eoseret/llm-attention/attention.cpp: 27 - 33

--------------------------------------------------------------------------------

27:       for (unsigned int j = 0; j < N; ++j) {  //vectorized

28:          double sum = 0.0;

29: #pragma clang loop vectorize(enable)

30:          for (unsigned int k = 0; k < K; ++k) { //vectorized

31:             sum += (double)A[i * K + k] * (double)B[k * N + j];

32:          }

33:          C[i * N + j] = alpha * static_cast<float>(sum);

Coverage (%)	Name	Source Location	Module

min	med	avg	max

Percentile Index	10	20	30	40	50	60	70	80	90	100
Value

min	med	avg	max

Percentile Index	10	20	30	40	50	60	70	80	90	100
Value

Path /

Metric	Value
CQA speedup if no scalar integer	1.02
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	8.17
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.02
Bottlenecks	micro-operation queue,
Function	main
Source	attention.cpp:27-27,attention.cpp:31-33
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	8.17
CQA cycles if no scalar integer	8.00
CQA cycles if FP arith vectorized	8.17
CQA cycles if fully vectorized	1.00
Front-end cycles	8.17
P0 cycles	7.50
P1 cycles	7.80
P2 cycles	1.00
P3 cycles	1.00
P4 cycles	4.00
P5 cycles	8.00
P6 cycles	2.60
P7 cycles	4.00
P8 cycles	4.00
P9 cycles	4.00
P10 cycles	2.40
P11 cycles	1.00
DIV/SQRT cycles	0.00
Inter-iter dependencies cycles	1
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	41.00
Nb uops	49.00
Nb loads	3.00
Nb stores	8.00
Nb stack references	3.00
FLOP/cycle	0.00
Nb FLOP add-sub	0.00
Nb FLOP mul	0.00
Nb FLOP fma	0.00
Nb FLOP div	0.00
Nb FLOP rcp	0.00
Nb FLOP sqrt	0.00
Nb FLOP rsqrt	0.00
Bytes/cycle	6.37
Bytes prefetched	0.00
Bytes loaded	20.00
Bytes stored	32.00
Stride 0	0.00
Stride 1	0.00
Stride n	1.00
Stride unknown	1.00
Stride indirect	0.00
Vectorization ratio all	29.63
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	0.00
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	50.00
Vector-efficiency ratio all	13.89
Vector-efficiency ratio load	9.38
Vector-efficiency ratio store	6.25
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	6.25
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	18.75

Metric	Value
CQA speedup if no scalar integer	1.02
CQA speedup if FP arith vectorized	1.00
CQA speedup if fully vectorized	8.17
CQA speedup if no inter-iteration dependency	NA
CQA speedup if next bottleneck killed	1.02
Bottlenecks	micro-operation queue,
Function	main
Source	attention.cpp:27-27,attention.cpp:31-33
Source loop unroll info	NA
Source loop unroll confidence level	NA
Unroll/vectorization loop type	NA
Unroll factor	NA
CQA cycles	8.17
CQA cycles if no scalar integer	8.00
CQA cycles if FP arith vectorized	8.17
CQA cycles if fully vectorized	1.00
Front-end cycles	8.17
P0 cycles	7.50
P1 cycles	7.80
P2 cycles	1.00
P3 cycles	1.00
P4 cycles	4.00
P5 cycles	8.00
P6 cycles	2.60
P7 cycles	4.00
P8 cycles	4.00
P9 cycles	4.00
P10 cycles	2.40
P11 cycles	1.00
DIV/SQRT cycles	0.00
Inter-iter dependencies cycles	1
FE+BE cycles (UFS)	NA
Stall cycles (UFS)	NA
Nb insns	41.00
Nb uops	49.00
Nb loads	3.00
Nb stores	8.00
Nb stack references	3.00
FLOP/cycle	0.00
Nb FLOP add-sub	0.00
Nb FLOP mul	0.00
Nb FLOP fma	0.00
Nb FLOP div	0.00
Nb FLOP rcp	0.00
Nb FLOP sqrt	0.00
Nb FLOP rsqrt	0.00
Bytes/cycle	6.37
Bytes prefetched	0.00
Bytes loaded	20.00
Bytes stored	32.00
Stride 0	0.00
Stride 1	0.00
Stride n	1.00
Stride unknown	1.00
Stride indirect	0.00
Vectorization ratio all	29.63
Vectorization ratio load	0.00
Vectorization ratio store	0.00
Vectorization ratio mul	NA
Vectorization ratio add_sub	0.00
Vectorization ratio fma	NA
Vectorization ratio div_sqrt	NA
Vectorization ratio other	50.00
Vector-efficiency ratio all	13.89
Vector-efficiency ratio load	9.38
Vector-efficiency ratio store	6.25
Vector-efficiency ratio mul	NA
Vector-efficiency ratio add_sub	6.25
Vector-efficiency ratio fma	NA
Vector-efficiency ratio div_sqrt	NA
Vector-efficiency ratio other	18.75

Path /

Average path: Display a virtual path defined by average values of all real paths

Function	main
Source file and lines	attention.cpp:27-33
Module	attention-avx512

The loop is defined in /home/eoseret/llm-attention/attention.cpp:27-33.

Analyzed code is defined in /home/eoseret/llm-attention/attention.cpp:27,31-33.

Warnings:
Non-innermost loop: analyzing only self part (ignoring child loops).

gain
potential
hint
expert

Vectorization

Your loop is probably not vectorized. Only 13% of vector register length is used (average across all SSE/AVX instructions). By vectorizing your loop, you can lower the cost of an iteration from 8.17 to 1.00 cycles (8.17x speedup).

Details

Store and arithmetical SSE/AVX instructions are used in scalar version (process only one data element in vector registers). Since your execution units are vector units, only a vectorized loop can use their full power.

Workaround

Try another compiler or update/tune your current one:
- recompile with ffast-math (included in Ofast) to extend loop vectorization to FP reductions.
Remove inter-iterations dependences from your loop and make it unit-stride:
- If your arrays have 2 or more dimensions, check whether elements are accessed contiguously and, otherwise, try to permute loops accordingly: C storage order is row-major: for(i) for(j) a[j][i] = b[j][i]; (slow, non stride 1) => for(i) for(j) a[i][j] = b[i][j]; (fast, stride 1)
- If your loop streams arrays of structures (AoS), try to use structures of arrays instead (SoA): for(i) a[i].x = b[i].x; (slow, non stride 1) => for(i) a.x[i] = b.x[i]; (fast, stride 1)

Execution units bottlenecks

Found no such bottlenecks but see expert reports for more complex bottlenecks.

No data for this section

Complex instructions

Detected COMPLEX INSTRUCTIONS.

Details

These instructions generate more than one micro-operation and only one of them can be decoded during a cycle and the extra micro-operations increase pressure on execution units.

VCVTSD2SS: 8 occurrences►
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33

Slow data structures access

Detected data structures (typically arrays) that cannot be efficiently read/written

Details

Constant unknown stride: 1 occurrence(s)
Constant non-unit stride: 1 occurrence(s)

Non-unit stride (uncontiguous) accesses are not efficiently using data caches

Workaround

Try to reorganize arrays of structures to structures of arrays
Consider to permute loops (see vectorization gain report)

Conversion instructions

Detected expensive conversion instructions.

Details

VCVTSD2SS (FP64 to FP32, scalar): 8 occurrences►
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33

Workaround

Avoid mixing data with different types. In particular, check if the type of constants is the same as array elements. Use double instead of single precision only when/where needed by numerical stability and avoid mixing precision. In C/C++, FP constants are double precision by default and must be suffixed by 'f' to make them single precision.

Type of elements and instruction set

No instructions are processing arithmetic or math operations on FP elements. This loop is probably writing/copying data or processing integer elements.

Matching between your loop (in the source code) and the binary loop

The binary loop does not contain any FP arithmetical operations. The binary loop is loading 20 bytes. The binary loop is storing 32 bytes.

General properties

nb instructions	41
nb uops	49
loop length	192
used x86 registers	9
used mmx registers	0
used xmm registers	8
used ymm registers	0
used zmm registers	0
nb stack references	3

Front-end

MACRO FUSION NOT POSSIBLE FIT IN UOP CACHE

micro-operation queue	8.17 cycles
front end	8.17 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11
uops	7.50	7.50	1.00	1.00	4.00	8.00	2.60	4.00	4.00	4.00	2.40	1.00
cycles	7.50	7.80	1.00	1.00	4.00	8.00	2.60	4.00	4.00	4.00	2.40	1.00

Execution ports to units layout:

P0 (256 bits): VPU, BRU, ALU, DIV/SQRT
P1 (256 bits): ALU, VPU
P2 (512 bits): load
P3 (512 bits): load
P4 (512 bits): store data
P5 (512 bits): ALU, VPU
P6: ALU, BRU
P7: store address
P8: store address
P9 (512 bits): store data
P10: ALU
P11 (512 bits): load

Cycles executing div or sqrt instructions	NA
Longest recurrence chain latency (RecMII)	1.00

Cycles summary

Front-end	8.17
Dispatch	8.00
Data deps.	1.00
Overall L1	8.17

Vectorization ratios

INT

all	0%
load	0%
store	NA (no store vectorizable/vectorized instructions)
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
other	NA (no other vectorizable/vectorized instructions)

all	33%
load	NA (no load vectorizable/vectorized instructions)
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

INT+FP

all	29%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

Vector efficiency ratios

INT

all	8%
load	9%
store	NA (no store vectorizable/vectorized instructions)
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	6%
fma	NA (no fma vectorizable/vectorized instructions)
other	NA (no other vectorizable/vectorized instructions)

all	14%
load	NA (no load vectorizable/vectorized instructions)
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

INT+FP

all	13%
load	9%
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	6%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 8.17 cycles. At this rate:

1% of peak load performance is reached (2.45 out of 192.00 bytes loaded per cycle (GB/s @ 1GHz))
3% of peak store performance is reached (3.92 out of 128.00 bytes stored per cycle (GB/s @ 1GHz))

Front-end bottlenecks

Performance is limited by instruction throughput (loading/decoding program instructions to execution core) (front-end is a bottleneck).

ASM code

In the binary file, the address of the loop is: 405050

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	Latency	Recip. throughput	Vectorization
LEA (,%R11,8),%EDX	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1-2	0.20	N/A
VXORPS %XMM7,%XMM7,%XMM7	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
MOV -0x40(%RBP),%R10D	1	0	0	0.33	0.33	0	0	0	0	0	0	0	0.33	1	0.33	scal (6.3%)
MOV %R9D,%ESI	1	0	0	0	0	0	0	0	0	0	0	0	0	1	0.17	N/A
MOV -0x70(%RBP),%RDI	1	0	0	0.33	0.33	0	0	0	0	0	0	0	0.33	1	0.33	scal (12.5%)
VXORPS %XMM8,%XMM8,%XMM8	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM9,%XMM9,%XMM9	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM10,%XMM10,%XMM10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM11,%XMM11,%XMM11	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM12,%XMM12,%XMM12	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM13,%XMM13,%XMM13	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM14,%XMM14,%XMM14	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
NOPW (%RAX,%RAX,1)	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
VCVTSD2SS %XMM14,%XMM14,%XMM14	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA (%RAX,%RDX,1),%ESI	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1-2	0.20	N/A
VMOVSS %XMM14,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM13,%XMM13,%XMM13	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x1(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM13,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM12,%XMM12,%XMM12	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x2(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM12,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM11,%XMM11,%XMM11	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x3(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM11,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM10,%XMM10,%XMM10	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x4(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM10,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM9,%XMM9,%XMM9	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x5(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM9,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM8,%XMM8,%XMM8	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x6(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM8,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM7,%XMM7,%XMM7	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x7(%RAX,%RDX,1),%EDX	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM7,(%RBX,%RDX,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
ADD $0x8,%R9D	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1	0.20	scal (6.3%)
CMP -0x60(%RBP),%R11	1	0.20	0.20	0.33	0.33	0	0.20	0.20	0	0	0	0.20	0.33	1	0.33	N/A
LEA 0x1(%R11),%R11	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
JNE 405050 <main+0x1250>	1	0.50	0	0	0	0	0	0.50	0	0	0	0	0	0	0.50	N/A

Function	main
Source file and lines	attention.cpp:27-33
Module	attention-avx512

gain
potential
hint
expert

Vectorization

Details

Workaround

Try another compiler or update/tune your current one:
- recompile with ffast-math (included in Ofast) to extend loop vectorization to FP reductions.
Remove inter-iterations dependences from your loop and make it unit-stride:
- If your arrays have 2 or more dimensions, check whether elements are accessed contiguously and, otherwise, try to permute loops accordingly: C storage order is row-major: for(i) for(j) a[j][i] = b[j][i]; (slow, non stride 1) => for(i) for(j) a[i][j] = b[i][j]; (fast, stride 1)
- If your loop streams arrays of structures (AoS), try to use structures of arrays instead (SoA): for(i) a[i].x = b[i].x; (slow, non stride 1) => for(i) a.x[i] = b.x[i]; (fast, stride 1)

Execution units bottlenecks

Found no such bottlenecks but see expert reports for more complex bottlenecks.

No data for this section

Complex instructions

Detected COMPLEX INSTRUCTIONS.

Details

These instructions generate more than one micro-operation and only one of them can be decoded during a cycle and the extra micro-operations increase pressure on execution units.

VCVTSD2SS: 8 occurrences►
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33

Slow data structures access

Detected data structures (typically arrays) that cannot be efficiently read/written

Details

Constant unknown stride: 1 occurrence(s)
Constant non-unit stride: 1 occurrence(s)

Non-unit stride (uncontiguous) accesses are not efficiently using data caches

Workaround

Try to reorganize arrays of structures to structures of arrays
Consider to permute loops (see vectorization gain report)

Conversion instructions

Detected expensive conversion instructions.

Details

VCVTSD2SS (FP64 to FP32, scalar): 8 occurrences►
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33
- /home/eoseret/llm-attention/attention.cpp:33

Workaround

Type of elements and instruction set

No instructions are processing arithmetic or math operations on FP elements. This loop is probably writing/copying data or processing integer elements.

Matching between your loop (in the source code) and the binary loop

The binary loop does not contain any FP arithmetical operations. The binary loop is loading 20 bytes. The binary loop is storing 32 bytes.

General properties

nb instructions	41
nb uops	49
loop length	192
used x86 registers	9
used mmx registers	0
used xmm registers	8
used ymm registers	0
used zmm registers	0
nb stack references	3

Front-end

MACRO FUSION NOT POSSIBLE FIT IN UOP CACHE

micro-operation queue	8.17 cycles
front end	8.17 cycles

Back-end

	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11
uops	7.50	7.50	1.00	1.00	4.00	8.00	2.60	4.00	4.00	4.00	2.40	1.00
cycles	7.50	7.80	1.00	1.00	4.00	8.00	2.60	4.00	4.00	4.00	2.40	1.00

Execution ports to units layout:

P0 (256 bits): VPU, BRU, ALU, DIV/SQRT
P1 (256 bits): ALU, VPU
P2 (512 bits): load
P3 (512 bits): load
P4 (512 bits): store data
P5 (512 bits): ALU, VPU
P6: ALU, BRU
P7: store address
P8: store address
P9 (512 bits): store data
P10: ALU
P11 (512 bits): load

Cycles executing div or sqrt instructions	NA
Longest recurrence chain latency (RecMII)	1.00

Cycles summary

Front-end	8.17
Dispatch	8.00
Data deps.	1.00
Overall L1	8.17

Vectorization ratios

INT

all	0%
load	0%
store	NA (no store vectorizable/vectorized instructions)
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
other	NA (no other vectorizable/vectorized instructions)

all	33%
load	NA (no load vectorizable/vectorized instructions)
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

INT+FP

all	29%
load	0%
store	0%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	0%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	50%

Vector efficiency ratios

INT

all	8%
load	9%
store	NA (no store vectorizable/vectorized instructions)
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	6%
fma	NA (no fma vectorizable/vectorized instructions)
other	NA (no other vectorizable/vectorized instructions)

all	14%
load	NA (no load vectorizable/vectorized instructions)
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	NA (no add-sub vectorizable/vectorized instructions)
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

INT+FP

all	13%
load	9%
store	6%
mul	NA (no mul vectorizable/vectorized instructions)
add-sub	6%
fma	NA (no fma vectorizable/vectorized instructions)
div/sqrt	NA (no div/sqrt vectorizable/vectorized instructions)
other	18%

Cycles and memory resources usage

Assuming all data fit into the L1 cache, each iteration of the binary loop takes 8.17 cycles. At this rate:

1% of peak load performance is reached (2.45 out of 192.00 bytes loaded per cycle (GB/s @ 1GHz))
3% of peak store performance is reached (3.92 out of 128.00 bytes stored per cycle (GB/s @ 1GHz))

Front-end bottlenecks

Performance is limited by instruction throughput (loading/decoding program instructions to execution core) (front-end is a bottleneck).

ASM code

In the binary file, the address of the loop is: 405050

Instruction	Nb FU	P0	P1	P2	P3	P4	P5	P6	P7	P8	P9	P10	P11	Latency	Recip. throughput	Vectorization
LEA (,%R11,8),%EDX	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1-2	0.20	N/A
VXORPS %XMM7,%XMM7,%XMM7	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
MOV -0x40(%RBP),%R10D	1	0	0	0.33	0.33	0	0	0	0	0	0	0	0.33	1	0.33	scal (6.3%)
MOV %R9D,%ESI	1	0	0	0	0	0	0	0	0	0	0	0	0	1	0.17	N/A
MOV -0x70(%RBP),%RDI	1	0	0	0.33	0.33	0	0	0	0	0	0	0	0.33	1	0.33	scal (12.5%)
VXORPS %XMM8,%XMM8,%XMM8	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM9,%XMM9,%XMM9	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM10,%XMM10,%XMM10	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM11,%XMM11,%XMM11	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM12,%XMM12,%XMM12	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM13,%XMM13,%XMM13	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
VXORPS %XMM14,%XMM14,%XMM14	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	vect (25.0%)
NOPW (%RAX,%RAX,1)	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
VCVTSD2SS %XMM14,%XMM14,%XMM14	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA (%RAX,%RDX,1),%ESI	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1-2	0.20	N/A
VMOVSS %XMM14,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM13,%XMM13,%XMM13	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x1(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM13,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM12,%XMM12,%XMM12	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x2(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM12,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM11,%XMM11,%XMM11	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x3(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM11,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM10,%XMM10,%XMM10	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x4(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM10,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM9,%XMM9,%XMM9	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x5(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM9,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM8,%XMM8,%XMM8	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x6(%RAX,%RDX,1),%ESI	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM8,(%RBX,%RSI,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
VCVTSD2SS %XMM7,%XMM7,%XMM7	2	0.50	0.50	0	0	0	1	0	0	0	0	0	0	5	1	scal (12.5%)
LEA 0x7(%RAX,%RDX,1),%EDX	1	0	1	0	0	0	0	0	0	0	0	0	0	3	1	N/A
VMOVSS %XMM7,(%RBX,%RDX,4)	1	0	0	0	0	0.50	0	0	0.50	0.50	0.50	0	0	1	0.50	scal (6.3%)
ADD $0x8,%R9D	1	0.20	0.20	0	0	0	0.20	0.20	0	0	0	0.20	0	1	0.20	scal (6.3%)
CMP -0x60(%RBP),%R11	1	0.20	0.20	0.33	0.33	0	0.20	0.20	0	0	0	0.20	0.33	1	0.33	N/A
LEA 0x1(%R11),%R11	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0.17	N/A
JNE 405050 <main+0x1250>	1	0.50	0	0	0	0	0	0.50	0	0	0	0	0	0	0.50	N/A

Report Configuration

Vectorization

Details

Workaround

Execution units bottlenecks

Complex instructions

Details

Slow data structures access

Details

Workaround

Conversion instructions

Details

Workaround

Type of elements and instruction set

Matching between your loop (in the source code) and the binary loop

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Vector efficiency ratios

Cycles and memory resources usage

Front-end bottlenecks

ASM code

Vectorization

Details

Workaround

Execution units bottlenecks

Complex instructions

Details

Slow data structures access

Details

Workaround

Conversion instructions

Details

Workaround

Type of elements and instruction set

Matching between your loop (in the source code) and the binary loop

General properties

Front-end

Back-end

Cycles summary

Vectorization ratios

Vector efficiency ratios

Cycles and memory resources usage

Front-end bottlenecks

ASM code