[ARM] Fix int8 NCHWc compute and alter layout #10839

masahi · 2022-03-31T03:45:17Z

This PR fixes a bug in TE ARM int8 compute for NCHWc conv2d, introduced in #10310. The compute itself, not the schedule, is broken for the following reasons:

We are using n_elems = 8 in

tvm/python/tvm/topi/arm_cpu/conv2d_alter_op.py

Line 350 in e9091d6

n_elems = 8

. Thus, the innermost axis of the transformed kernel has extent 8:

tvm/python/tvm/topi/arm_cpu/conv2d_alter_op.py

Line 375 in e9091d6

new_attrs["kernel_layout"] = "OIHW{:n}i{:n}o{:n}i".format(ic_bn // n_elems, oc_bn, n_elems)
In the TE compute, we iterate over the innermost axis ic_s_inner of the kernel at

tvm/python/tvm/topi/nn/conv2d.py

Line 577 in f6f252f

* kernel[oc_chunk, ic_outer, kh, kw, ic_f_inner, oc_block, ic_s_inner].astype(

. ic_s_inner has extent n_elems according to

tvm/python/tvm/topi/nn/conv2d.py

Line 566 in f6f252f

ic_s_inner = te.reduce_axis((0, n_elems), name="ic_s_inner")

. n_elems is 4 by default according to

tvm/python/tvm/topi/nn/conv2d.py

Line 478 in f6f252f

data, kernel, stride, padding, dilation, layout, out_layout, out_dtype="int32", n_elems=4

The ARM code that calls this compute does not explicitly pass n_elems, according to

tvm/python/tvm/topi/arm_cpu/conv2d_int8.py

Lines 106 to 108 in e9091d6

    
           return nn.conv2d_NCHWc_int8( 
        
               data, kernel, strides, padding, dilation, layout, out_layout, out_dtype 
        
           )

Thus, even though the innermost axis of the kernel has extent 8, the TE compute only loops over n_elems = 4 of the input channel dimension.

Initially, I tried to keep n_elems = 8 in alter layout and fix the intrinsic definition. But n_elems = 8 breaks tensorization pattern matching, since now the compute is doing 4x8 innermost loop but this intrinsic is supposed to do 4x4 dot product, see

tvm/python/tvm/topi/arm_cpu/tensor_intrin.py

Lines 467 to 479 in 7896108

    
           num_int8_elements = 4  # 4 int8 elements in int32 
        
           data = te.placeholder((num_int8_elements,), dtype="%s8" % dtype, name="data") 
        
           kernel = te.placeholder((int32_lanes, num_int8_elements), dtype="%s8" % dtype, name="kernel") 
        
           k = te.reduce_axis((0, num_int8_elements), name="k") 
        
           C = te.compute( 
        
               (int32_lanes,), 
        
               lambda i: te.sum( 
        
                   data[k].astype("%s32" % dtype) * kernel[i, k].astype("%s32" % dtype), axis=k 
        
               ), 
        
               name="C", 
        
           )

. Setting num_int8_elements = 8 there does fix the tensorize pattern matching, but the result was still incorrect.

Rather than fixing the intrin implementation in

tvm/python/tvm/topi/arm_cpu/tensor_intrin.py

Line 492 in 7896108

def _intrin_func(ins, outs):

to adapt for 4x8 dot product, I settled on setting n_elems = 4 in alter layout. It turned out this change is enough to get the correct output. Moreover, n_elems = 8 is simply wrong for the dot product path in

tvm/python/tvm/topi/arm_cpu/conv2d_int8.py

Lines 154 to 155 in 7896108

    
           if is_dotprod_available(): 
        
               intrin = dot_int8_int8_int32_neon_82(int32_lanes=4, dtype=dtype)

which computes 4x4 dot product in one instruction.

@tkonolige I suggest doing perf benchmark again, since the numbers in #10310 are invalid.

cc @mbrookhart @Mousius @junrushao1994 @vinx13

masahi · 2022-03-31T04:35:43Z

tests/python/topi/python/test_topi_conv2d_int8.py

@@ -364,7 +365,7 @@ def get_ref_data():
        # ),
    ]

-    # TODO(tvm-team): Properly run ARM code on CI aarch64 environment
+    # TODO(tvm-team): Figure out ARM dot product availability on CI aarch64 environment


cc @Mousius @u99127, I'd love to test the dot-product schedule on the aarch64 CI, do you know if it is supposed? Automatic detection would require /proc/cpuinfo etc as suggested by @u99127 in #10773 (comment), which I'd rather avoid.

As far as I know, the CI environment should be good to run the dot-product schedules, I can take a look at cpuinfo detection later 😸

yup I enabled the dot product test on CI, it seems to be working!

https://ci.tlcpack.ai/blue/rest/organizations/jenkins/pipelines/tvm/branches/PR-10839/runs/5/nodes/316/steps/542/log/?start=0
(Search Running on target: llvm -device arm_cpu -mtriple aarch64-linux-gnu -mattr=+neon,+v8.2a,+dotprod)

python/tvm/topi/arm_cpu/tensor_intrin.py

masahi · 2022-03-31T10:00:03Z

python/tvm/topi/x86/conv2d_int8.py

@@ -120,7 +120,7 @@ def _pack_data(cfg, data, kernel):
    kernel = te.compute(
        (oc_chunk, ic_chunk, kh, kw, ic_bn // n_elems, oc_bn, n_elems),
        lambda occ, icc, k_h, k_w, icbc, ocb, icbb: kernel[
-            occ * oc_bn + ocb, icc * ic_bn + icbc * ic_bn // n_elems + icbb, k_h, k_w
+            occ * oc_bn + ocb, icc * ic_bn + icbc * n_elems + icbb, k_h, k_w


cc @tkonolige please have a look at this change. Since test_topi_conv2d_int8.py doesn't use the alter layout code (which had a bug), and _pack_data is using n_elems = 4, the reason aarch64 CI failed on test_topi_conv2d_int8.py was probably due to this bug.

tkonolige

Thanks for fixing this @masahi! After reading through the code again (that I wrote...), it is doing a 4x4 dot product, so n_elems should be 4.

@tkonolige

This PR fixes a bug in TE ARM int8 compute for NCHWc conv2d, introduced in apache#10310. The compute itself, not the schedule, is broken for the following reasons: * We are using `n_elems = 8` in https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_alter_op.py#L350. Thus, the innermost axis of the transformed kernel has extent 8: https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_alter_op.py#L375 * In the TE compute, we iterate over the innermost axis `ic_s_inner` of the kernel at https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L577. `ic_s_inner` has extent `n_elems` according to https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L566. `n_elems` is 4 by default according to https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L478 * The ARM code that calls this compute does not explicitly pass `n_elems`, according to https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_int8.py#L106-L108 * Thus, even though the innermost axis of the kernel has extent 8, the TE compute only loops over `n_elems = 4` of the input channel dimension. Initially, I tried to keep `n_elems = 8` in alter layout and fix the intrinsic definition. But `n_elems = 8` breaks tensorization pattern matching, since now the compute is doing 4x8 innermost loop but this intrinsic is supposed to do 4x4 dot product, see https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/tensor_intrin.py#L467-L479. Setting `num_int8_elements = 8` there does fix the tensorize pattern matching, but the result was still incorrect. Rather than fixing the intrin implementation in https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/tensor_intrin.py#L492 to adapt for 4x8 dot product, I settled on setting `n_elems = 4` in alter layout. It turned out this change is enough to get the correct output. Moreover, `n_elems = 8` is simply wrong for the dot product path in https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/conv2d_int8.py#L154-L155 which computes 4x4 dot product in one instruction. @tkonolige I suggest doing perf benchmark again, since the numbers in apache#10310 are invalid. cc @mbrookhart @Mousius @junrushao1994 @vinx13

@tkonolige

This PR fixes a bug in TE ARM int8 compute for NCHWc conv2d, introduced in apache#10310. The compute itself, not the schedule, is broken for the following reasons: * We are using `n_elems = 8` in https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_alter_op.py#L350. Thus, the innermost axis of the transformed kernel has extent 8: https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_alter_op.py#L375 * In the TE compute, we iterate over the innermost axis `ic_s_inner` of the kernel at https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L577. `ic_s_inner` has extent `n_elems` according to https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L566. `n_elems` is 4 by default according to https://github.com/apache/tvm/blob/f6f252f0abc8f621a96506739f9534083d1fe213/python/tvm/topi/nn/conv2d.py#L478 * The ARM code that calls this compute does not explicitly pass `n_elems`, according to https://github.com/apache/tvm/blob/e9091d6c68d5d70c28881e5c75bfe72e385c1f4d/python/tvm/topi/arm_cpu/conv2d_int8.py#L106-L108 * Thus, even though the innermost axis of the kernel has extent 8, the TE compute only loops over `n_elems = 4` of the input channel dimension. Initially, I tried to keep `n_elems = 8` in alter layout and fix the intrinsic definition. But `n_elems = 8` breaks tensorization pattern matching, since now the compute is doing 4x8 innermost loop but this intrinsic is supposed to do 4x4 dot product, see https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/tensor_intrin.py#L467-L479. Setting `num_int8_elements = 8` there does fix the tensorize pattern matching, but the result was still incorrect. Rather than fixing the intrin implementation in https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/tensor_intrin.py#L492 to adapt for 4x8 dot product, I settled on setting `n_elems = 4` in alter layout. It turned out this change is enough to get the correct output. Moreover, `n_elems = 8` is simply wrong for the dot product path in https://github.com/apache/tvm/blob/7896108fc41663a1fecbb52345194a93278e9e28/python/tvm/topi/arm_cpu/conv2d_int8.py#L154-L155 which computes 4x4 dot product in one instruction. @tkonolige I suggest doing perf benchmark again, since the numbers in apache#10310 are invalid. cc @mbrookhart @Mousius @junrushao1994 @vinx13

masahi changed the title ~~[ARM] Fix int8 NCHWc compute and tensor intrin for non dot product path~~ [ARM] Fix int8 NCHWc compute and tensor intrin for non dot product path (rpi etc) Mar 31, 2022

masahi mentioned this pull request Mar 31, 2022

[Tracking Issue] Enabling Testing in AArch64 #10673

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masahi changed the title ~~[ARM] Fix int8 NCHWc compute and tensor intrin for non dot product path (rpi etc)~~ [ARM] Fix int8 NCHWc compute and alter layout Mar 31, 2022

github-actions bot requested review from Mousius and mbrookhart March 31, 2022 04:33

masahi commented Mar 31, 2022

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masahi commented Mar 31, 2022

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tkonolige approved these changes Mar 31, 2022

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masahi added 8 commits April 1, 2022 04:16

[ARM] pass correct n_elems in NCHWc compute definition

6a2b82c

schedule with dot product intrin computes correct output

329a7b4

[ARM] Fix int8 NCHWc compute and tensor intrin for non dot product path

b939620

enable neon test on aarch64 CI

bb5f1de

lint

1cc8aca

Correctly account for n_elems when input is NCHW

05d50b3

fixed pack_data

b6729a5

try run dot product schedule on CI

53ff53e

masahi force-pushed the arm-nchwc-conv2d-fix branch from 32916b6 to 53ff53e Compare March 31, 2022 19:17

mbrookhart approved these changes Mar 31, 2022

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junrushao approved these changes Mar 31, 2022

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junrushao merged commit 912993f into apache:main Apr 1, 2022

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[ARM] Fix int8 NCHWc compute and alter layout #10839

[ARM] Fix int8 NCHWc compute and alter layout #10839

masahi commented Mar 31, 2022 •

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tkonolige left a comment

	return nn.conv2d_NCHWc_int8(
	data, kernel, strides, padding, dilation, layout, out_layout, out_dtype
	)

	num_int8_elements = 4 # 4 int8 elements in int32

	data = te.placeholder((num_int8_elements,), dtype="%s8" % dtype, name="data")
	kernel = te.placeholder((int32_lanes, num_int8_elements), dtype="%s8" % dtype, name="kernel")

	k = te.reduce_axis((0, num_int8_elements), name="k")
	C = te.compute(
	(int32_lanes,),
	lambda i: te.sum(
	data[k].astype("%s32" % dtype) * kernel[i, k].astype("%s32" % dtype), axis=k
	),
	name="C",
	)

	if is_dotprod_available():
	intrin = dot_int8_int8_int32_neon_82(int32_lanes=4, dtype=dtype)

[ARM] Fix int8 NCHWc compute and alter layout #10839

[ARM] Fix int8 NCHWc compute and alter layout #10839

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