Merge branch 'master' of https://github.com/boennecd/parglm

R/parglm.R

@@ -66,7 +66,7 @@ parglm <- function(
   contrasts = NULL, model = TRUE, x = FALSE, y = TRUE, ...){
   cl <- match.call()
   cl[[1L]] <- quote(glm)
-  cl[c("method", "singular.ok")] <- list(quote(parglm.fit), FALSE)
+  cl[c("method", "singular.ok")] <- list(quote(parglm::parglm.fit), FALSE)
   eval(cl, parent.frame())
 }
 
@@ -170,6 +170,21 @@ parglm.fit <- function(
   if (is.null(offset))
     offset <- rep.int(0, nobs)
 
+  n_min_per_thread <- 10L
+  n_per_thread <- nrow(x) / control$nthreads
+  if(n_per_thread < n_min_per_thread){
+    nthreads_new <- nrow(x) %/% n_min_per_thread
+    if(nthreads_new < 1L)
+      nthreads_new <- 1L
+
+    warning(
+      "Too few observation compared to the number of threads. ",
+      nthreads_new, " thread(s) will be used instead of ",
+      control$nthreads, ".")
+
+    control$nthreads <- nthreads_new
+  }
+
   block_size <- if(!is.null(control$block_size))
     control$block_size else
       if(control$nthreads > 1L)

tests/testthat/test_misc.R

@@ -0,0 +1,32 @@
+context("Miscellaneous tests")
+
+test_that("'parglm' works when package is not attached",{
+  # Issue: https://github.com/boennecd/parglm/issues/2#issue-397286510
+  # See https://github.com/r-lib/devtools/issues/1797#issuecomment-423288947
+
+  expect_silent(
+    local({
+      detach("package:parglm", unload = TRUE, force = TRUE)
+      parglm::parglm(mpg ~ gear , data = datasets::mtcars)
+      library(parglm)
+    },
+    envir= new.env(parent = environment(glm))))
+})
+
+test_that("Using more threads then rows yields a warning", {
+  # Issue: https://github.com/boennecd/parglm/issues/3#issue-399052270
+
+  this_df <- data.frame( a = sample( 1:1000000 , 20 ) / 100 , b = 1 )
+  expect_warning(
+    parglm( a ~ b - 1, data = this_df , nthreads = 64),
+    regexp = "Too few observation compared to the number of threads. 2 thread(s) will be used instead of 64.",
+    fixed = TRUE)
+
+  # should yield one thread (the number of rows is less than the number required
+  # per thread)
+  this_df <- data.frame( a = sample( 1:1000000 , 5 ) / 100 , b = 1 )
+  expect_warning(
+    parglm( a ~ b - 1, data = this_df , nthreads = 64),
+    regexp = "Too few observation compared to the number of threads. 1 thread(s) will be used instead of 64.",
+    fixed = TRUE)
+})