Meeting notes and slides for 19 September 2023

Samsung SAIT presentation about SYCL PIM language extensions

Author: Ruyman Reyes Castro

language/README.rst

@@ -23,10 +23,156 @@ Potential Topics
 * Function pointers revisited
 * oneDPL C++ standard library support
 
+2023-09-19
+=============
+
+* Ruyman Reyes (Intel/Codeplay)
+* Lukas Sommer (Codeplay Software Ltd)
+* Benie (Codeplay Software Ltd)
+* Hyesun Hong (Samsung SAIT)
+* Julian Oppermann (Codeplay Software Ltd)
+* Mehdi Goli (Codeplay Software Ltd)
+* Lueck, Gregory (Intel)
+* Jesus Labarta (BSC) (Guest)
+* Brodman, James (Intel)
+* Hanwoong Jung (Samsung SAIT)
+* Brice Goglin (Invité)
+* Plaska, Oskar (Contractor, Cognizant)
+* Tom Deakin (Univ. of Bristol)
+* Marcin (N/A)
+* Victor Lomuller (Codeplay Software Ltd)
+* Biagio COSENZA (Università degli Studi di Salerno)
+* Voss, Michael J (Intel)
+* Kukanov, Alexey (Intel)
+* Richards, Alison L (Intel)
+* Adam Kuźniar (Mobica)
+* Slavova, Gergana S (Intel)
+* bongjun kim (Samsung SAIT)
+* Keryell, Ronan (XILINX LABS)
+* Juan Fumero (University of Manchester)
+* Gordon Brown (Codeplay Software Ltd)
+* Tim (N/A)
+* Kinsner, Michael (Intel)
+* Petersen, Paul (Intel)
+* Videau, Brice (ANL)
+* Holmes, Daniel John (Intel)
+* Frank Brill (Cadence)
+* Mrozek, Michal (Intel)
+* Reble, Pablo (Intel)
+* Andrew Richards (Intel/Codeplay)
+* Smith, Timmie (Intel)
+
+
+SYCL Extension Proposal for PIM/PNM
+--------------------------------------
+
+Hyesun Hong,
+`Slides <presentation/2023-09-19-HS-sycl-pim-extensions.pdf>`
+
+* PIM/PNM technology enables computation directly on memory
+* Prevents data movement improving performance and reducing consumption
+* Operates directly on memory banks by reading and storing on rows and columns
+* Aquabolt-XL is the first demonstrator
+* Can be drop in on any memory controller
+* CXL-PNM is the CXL variant for PNM, can work with multiple PIM
+
+SYCL Extension for PIM/PNM
+* Work in collaboration with Codeplay Software team
+* Goals
+
+  * Seamlessly integrate PIM/PNM operation into SYCL
+  * Allow combination of xGPU and PIM/PNM in one device kernel
+  * Not specific to one hardware
+
+* Design
+
+  * Vector operation seem like natural fit
+  * no convergence guarantee and vector size explicit
+
+* Model as special function unit
+
+  * Aligns with trends to model special functional units inside accelerators
+  * Compiler automatic mapping often not possible
+  * joint_matrix-like interface
+
+
+* Group functions
+
+  * Easy to use
+  * Can easily be combined with device code
+  * Give necessary convergence guarantees
+
+
+* Recap of SYCL work-item, work-group and group functions
+
+  * Group functions must be encountered in converged control flow
+
+* Extension
+
+  * Extended group functions with additional overload of joint_reduce
+  * and new joint_transform and joint_inner_product
+  * Block size as template parameter, number of blocks as runtime parameter
+  * allows calculation of number of elements to process
+
+* Extension for PNM
+
+  * Added new overloads of joint_exclusive_scan,
+  * joint_inclusive_scan, reduce_over_group
+
+* PNM standalone has less opportunity for parallelism
+
+  * limited by memory controller
+  * -> Combine PNM and PIM, PNM generates commands for PIM blocks
+
+* Two modes
+
+  * PIM mode: PIM blocks can operate independently, can choose number of blocks
+  * PNM mode: Synchronized execution on multiple PIM blocks
+
+* Mapping
+
+  * Every PIM block is one work-item
+  * PNM with attached PIM blocks forms one work-group
+
+* Execution
+
+  * Work-item operations map to PIM operation
+  * Group functions map to PNM operation
+
+* Example
+
+  * work-item execution maps to PIM
+  * group function maps to PNM
+
+* Conclusion
+
+  * Integrate support for PIM/PNM into SYCL
+
+Q&A
+* Are the proposed functions specific to PIM, could also be used with other HW?
+
+  * Can also be used with other hardware.
+  * Semantics not PIM-specific, but translation of C++ to SYCL
+  * Can also map nicely to other types of hardware, e.g. vector processor
+
+* Why have the user explicitly specify a block-size?
+
+  * Not a hardware detail
+  * Rather a promise by the user that data-blocks
+    will always be at least that big
+  * Promise allows device compiler to perform optimizations,
+    efficient looping inside PIM unit
+
+* Could num_blocks runtime parameter be replaced by iterator?
+
+  * requires to be divisable by block-size
+  * Yes, that is possible, mainly a design question
+  * Current version might have additional implications regarding alignment
+
+
 2023-06-05
 ==========
 
-
 * Ruyman Reyes
 * Rod Burns
 * Cohn, Robert S