refactor: update instructions and configuration settings for webgraph

          processing. Adapt to settings used to build
          cc-main-2025-jan-feb-mar on Ubuntu 24.04 ARM using Java 21

Author: sebastian-nagel

src/script/webgraph_ranking/run_webgraph.sh

@@ -35,8 +35,7 @@ case "$1" in
         # Java options for HyperBall, recommended in
         #  https://webgraph.di.unimi.it/docs/it/unimi/dsi/webgraph/algo/HyperBall.html
         JAVA_OPTS="$JAVA_OPTS -server -Xss256K -XX:PretenureSizeThreshold=512M -XX:MaxNewSize=$(($MEMMB/3))m \
-          -XX:+UseNUMA -XX:+UseTLAB -XX:+ResizeTLAB \
-          -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=99 -XX:+UseCMSInitiatingOccupancyOnly"
+          -XX:+UseNUMA -XX:+UseTLAB -XX:+ResizeTLAB"
     ;;
 esac
 

src/script/webgraph_ranking/webgraph_config.sh

@@ -11,34 +11,29 @@ USE_WEBGRAPH_BIG=${USE_WEBGRAPH_BIG:-false}
 JOIN_RANKS_IN_MEMORY=${JOIN_RANKS_IN_MEMORY:-true}
 
 
-# number of threads and Hyperball registers
-# depend on the size of the machine (here EC2 instance)
-# ... and of the graph to be processed
-# => it's only an empirical value and possibly needs to be adjusted
-THREADS=${THREADS:-2}
-HYP_REG=4
-## on r4.8xlarge (244 GB)
-#THREADS=32
-#HYP_REG=4   # 4-5 for hostgraph, 10 for domain graph
-## on r4.16xlarge (488 GB)
-#THREADS=64
-#HYP_REG=5   # 4-6 for hostgraph, 10 for domain graph
-## on r5.12xlarge (384 GB)
-#THREADS=48
-#HYP_REG=5   # 4-6 for hostgraph, 10 for domain graph
-## on x1.16xlarge (976 GB)
-#THREADS=64
-#HYP_REG=9
-## on x1.32xlarge (1952 GB)
-#THREADS=128
-#HYP_REG=10
-
-# determine automatically, using java.lang.Runtime.availableProcessors()
-# THREADS=0
-
 # number of registers used for Hyperball / harmonic centrality calculation
+#
+# The number of Hyperball registers depend on
+# - the size of the machine (here EC2 instance)
+# - and of the graph to be processed
+# => it's an empirically determined value and
+#    possibly needs to be adjusted
+# It can be overridden by the environment variable
+# HYPERBALL_REGISTERS, see below.
+HYP_REG=12
+## on r8.24.xlarge (768 GB, 96 CPUs)
+#HYP_REG=10 (host-level graph, 300M nodes)
+#HYP_REG=12 (domain-level graph, 130M nodes)
+
 HYPERBALL_REGISTERS=${HYPERBALL_REGISTERS:-$HYP_REG}
 
+# number of threads
+# THREAD=0 : let the webgraph tools decide how many threads,
+#            given the available CPU cores, using
+#            java.lang.Runtime.availableProcessors()
+THREADS=${THREADS:-0}
+
+
 
 # number of fields in vertices file(s)
 #  (default: 2)