Also test on Linux ARM in R-CMD-check

.github/workflows/R-CMD-check.yml

@@ -34,6 +34,8 @@ jobs:
           - {os: ubuntu-latest,  r: 'oldrel-1'}
           - {os: ubuntu-latest,  r: 'oldrel-2'}
           - {os: ubuntu-latest,  r: 'oldrel-3'}
+
+          - {os: ubuntu-24.04-arm,  r: 'release'}
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}

R/Utility.R

@@ -1,7 +1,11 @@
 stdThreadMax <- function() {
     nThreads <- .Call(`_RcppAlgos_cpp11GetNumThreads`)
-    if (nThreads < 1L || is.na(nThreads) || is.null(nThreads)) nThreads = 1L
-    return(nThreads)
+
+    if (is.null(nThreads) || is.na(nThreads) || nThreads < 1L) {
+        nThreads <- 1L
+    }
+
+    as.integer(nThreads)
 }
 
 GetV <- function(v) {

R/zzz.R

@@ -5,53 +5,21 @@ pkgEnv$nCores <- NULL
 pkgEnv$maxThreads <- NULL
 
 physicalCoreCount <- function() {
+    ## Estimate physical cores using R's default detection path. This value is
+    ## used for cache-size heuristics, not as the authoritative thread limit.
+    ## If physical core detection is unavailable, fall back to logical cores
+    ## and finally to 1.
+    n <- parallel::detectCores(logical = FALSE)
+
+    if (is.na(n) || n < 1L) {
+        n <- parallel::detectCores(logical = TRUE)
+    }
 
-    if (grepl("darwin|solaris", R.version$os) || .Platform$OS.type == "windows")
-        return(parallel::detectCores(logical = FALSE))
-
-    ## According to R News as of # 3.4.4
-    ##    "parallel::detectCores(logical = FALSE) is ignored on Linux systems, since
-    ##                     the information is not available with virtualized OSes."
-    ##
-    ## This implementation tries the old command available from version 3.3.0 until
-    ## 3.4.3 (It was removed in 3.4.4), as I have had success with this command on
-    ## several Linux flavors. If this fails, we also try the method outlined
-    ## by user teambob in an answer to:
-    ##       "How to obtain the number of CPUs/cores in Linux from the command line?"
-    ## https://stackoverflow.com/a/18051445/4408538
-    ##
-    ## Otherwise, the implementation below is nearly identical to parallel::detectCores
-    ## with the argument logical set to FALSE. You will note that we have excluded
-    ## freevsd, openbsd, & irix as they do not have this option available.
-
-    systems <- list(linux = c("cat /proc/cpuinfo | grep 'cpu cores'| uniq | cut -f2 -d:",
-                              "grep '^core id' /proc/cpuinfo |sort -u|wc -l"),
-                    darwin = "/usr/sbin/sysctl -n hw.physicalcpu 2>/dev/null",
-                    solaris = "/bin/kstat -p -m cpu_info | grep :core_id | cut -f2 | uniq | wc -l")
-
-    for (i in seq(systems)) if (grepl(paste0("^", names(systems)[i]), R.version$os))
-        for (cmd in systems[i]) {
-            if (is.null(a <- tryCatch(suppressWarnings(
-                system(cmd, TRUE)), error = function(e) NULL))) {next}
-
-            a <- gsub("^ +", "", a[1])
-            if (grepl("^[1-9]", a))
-                return(as.integer(a))
-        }
-
-    ## if the above fails, we try all of them
-    for (i in seq(systems))
-        for (cmd in systems[i]) {
-            if (is.null(a <- tryCatch(suppressWarnings(
-                system(cmd, TRUE)), error = function(e) NULL))) {next}
-
-            a <- gsub("^ +", "", a[1])
-            if (grepl("^[1-9]", a))
-                return(as.integer(a))
-        }
-
-    ## If we get here, we assume 1 core
-    1L
+    if (is.na(n) || n < 1L) {
+        1L
+    } else {
+        as.integer(n)
+    }
 }
 
 ## This will set the maximum number of cores
@@ -62,10 +30,10 @@ physicalCoreCount <- function() {
     pkgEnv$nCores <- physicalCoreCount()
     tempThreads <- stdThreadMax()
 
-    if (is.na(tempThreads)) {
-        pkgEnv$maxThreads <- 1L
+    pkgEnv$maxThreads <- if (is.na(tempThreads) || tempThreads < 1L) {
+        1L
     } else {
-        pkgEnv$maxThreads <- tempThreads
+        as.integer(tempThreads)
     }
 
     invisible()