**Revision History**
-* v0.00 05may2021 first created
-* v0.01 06may2021 initial first draft
-* v0.02 08may2021 add scenarios / use-cases
-* v0.03 09may2021 add draft image for scenario
+* v0.00 05may2022 first created
+* v0.01 06may2022 initial first draft
+* v0.02 08may2022 add scenarios / use-cases
+* v0.03 09may2022 add draft image for scenario
+* v0.04 14may2022 add appendix with other research
+* v0.05 14jun2022 update images (thanks to Veera)
**Table of Contents**
Andes in Audio DSPs, WD in HDDs and SSDs. These are all
astoundingly commercially successful
multi-billion-unit mass volume markets that almost nobody
- knows anything about. Included for completeness.
+ knows anything about, outside their specialised proprietary
+ niche. Included for completeness.
In order of least controlled to most controlled, the viable
candidates for further advancement are:
that require significant programming effort in other ISAs.
All of these things come entirely from "Augmentation" of the Scalar operation
-being prefixed: at no time is the Scalar operation significantly
-altered.
+being prefixed: at no time is the Scalar operation's binary pattern decoded
+differently compared to when it is used as a Scalar operation.
From there, several more "Modes" can be added, including
* saturation,
Boolean Logic in a Vector context, on top of an already-powerful
Scalar Branch-Conditional/Counter instruction
+All of these festures are added as "Augmentations", to create of
+the order of 1.5 *million* instructions, none of which decode the
+32-bit scalar suffix any differently.
+
**What is missing from Power Scalar ISA that a Vector ISA needs?**
Remarkably, very little: the devil is in the details though.
why Matrix Multiplication Schedules may not be applied to Integer
Mul-and-Accumulate, Galois Field Mul-and-Accumulate, Logical
AND-and-OR, or any other future instruction such as Complex-Number
-Multiply-and-Accumulate that a future version of the Power ISA might
+Multiply-and-Accumulate or Abs-Diff-and-Accumulate
+that a future version of the Power ISA might
support. The flexibility is not only enormous, but the compactness
-unprecedented. RADIX2 in-place DCT Triple-loop Schedules may be created in
-around 11 instructions. The only other processors well-known to have
+unprecedented. RADIX2 in-place DCT may be created in
+around 11 instructions using the Triple-loop DCT Schedule. The only other processors well-known to have
this type of compact capability are both VLIW DSPs: TI's TMS320 Series
and Qualcom's Hexagon, and both are targetted at FFTs only.
in Multi-Chip-Module (aka "Chiplet") form, giving all the advantages of
the performance boost that goes with smaller line-drivers.
-
-Draft Image (placeholder):
-
-<img src="/openpower/sv/bridge_phy.jpg" width=800 />
+<img src="/openpower/sv/bridge_phy.svg" width=600 />
# Transparently-Distributed Vector Processing
**Use-case: Matrix and Convolutions**
+DRAFT image:
+
+<img src="https://ftp.libre-soc.org/20220614_122128.jpg" width=600 />
+
First, some important definitions, because there are two different
Vectorisation Modes in SVP64:
moving to next **element**. Currently managed by `svstep`,
ZOLC may be deployed to manage the stepping, in a Deterministic manner.
+Second:
+SVP64 Draft Matrix Multiply is currently set up to arrange a Schedule
+of Multiply-and-Accumulates, suitable for pipelining, that will,
+ultimately, result in a Matrix Multiply. Normal processors are forced
+to perform "loop-unrolling" in order to achieve this same Schedule.
+SIMD processors are further forced into a situation of pre-arranging rotated
+copies of data if the Matrices are not exactly on a power-of-two boundary.
+
+The current limitation of SVP64 however is (when Horizontal-First
+is deployed, at least, which is the least number of instructions)
+that both source and destination Matrices have to be in-registers,
+in full. Vertical-First may be used to perform a LD/ST within
+the loop, covered by `svstep`, but it is still not ideal. This
+is where the Snitch and EXTRA-V concepts kick in.
+
+<img src="https://ftp.libre-soc.org/matrix_svremap.jpg" width=600 />
+
Imagine a large Matrix scenario, with several values close to zero that
could be skipped: no need to include zero-multiplications, but a
traditional CPU in no way can help: only by loading the data through
conditional execution of the Multiply-and-Accumulate.
Horizontal-First Mode is the standard Cray-Style Vectorisation:
loop on all *elements* with the same instruction before moving
-on to the next instruction. Predication needs to be pre-calculated
+on to the next instruction. Horizontal-First
+Predication needs to be pre-calculated
for the entire Vector in order to exclude certain elements from
the computation. In this case, that's an expensive inconvenience
-(similar to the problems associated with Memory-to-Memory
+(remarkably similar to the problems associated with Memory-to-Memory
Vector Machines such as the CDC Star-100).
Vertical-First allows *scalar* instructions and
Draft Image (placeholder):
-<img src="/openpower/sv/zolc_svp64_extrav.jpg" width=800 />
+<img src="/openpower/sv/zolc_svp64_extrav.svg" width=800 />
The program being executed is a simple loop with a conditional
test that ignores the multiply if the input is zero.
standing problem facing Computer Science and doing so in a way that
reduces power consumption reduces algorithm completion time and reduces
the need for complex hardware microarchitectures in favour of much
-smaller distributed coherent Processing Elements.
+smaller distributed coherent Processing Elements with a Heterogenous ISA
+across the board.
# Appendix
in power. The article notes, pointedly, that programmability will
be a key deciding factor. The article also notes that Samsung has
proposed its architecture as a JEDEC Standard.
+
+**PIM-HBM Research**
+
+[Presentation](https://ieeexplore.ieee.org/document/9073325/) by Seongguk Kim
+and associated [video](https://www.youtube.com/watch?v=e4zU6u0YIRU)
+showing 3D-stacked DRAM connected to GPUs, but notes that even HBM, due to
+large GPU size, is less advantageous than it should be. Processing-in-Memory
+is therefore logically proposed. the PE (named a Streaming Multiprocessor)
+is much more sophisticated, comprising Register File, L1 Cache, FP32, FP64
+and a Tensor Unit.
+
+<img src="/openpower/sv/2022-05-14_11-55.jpg" width=500 />
+
+**etp4hpc.eu**
+
+[ETP 4 HPC](https://etp4hpc.eu) is a European Joint Initiative for HPC,
+with an eye towards
+[Processing in Memory](https://www.etp4hpc.eu/pujades/files/ETP4HPC_WP_Processing-In-Memory_FINAL.pdf)
+
+**Salient Labs**
+
+[Research paper](https://arxiv.org/abs/2002.00281) explaining
+that they can exceed a 14 ghz clock rate Multiply-and-Accumulate
+using Photonics.
+
+**SparseLNR**
+
+[SparseLNR](https://arxiv.org/abs/2205.11622) restructures sparse
+tensor computations using loop-nest restructuring.
+
+**Additional ZOLC Resources**
+
+* <https://www.researchgate.net/publication/3351728_Zero-overhead_loop_controller_that_implements_multimedia_algorithms>
projects / libreriscv.git / blobdiff