add comment describing why a locale's region of a file should be skip…

…ped if it's size is one Signed-off-by: Jeremiah Corrado <[email protected]>
chapel-lang · Sep 24, 2024 · 64ac575 · 64ac575
1 parent 03e5621
commit 64ac575
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diff --git a/modules/packages/ParallelIO.chpl b/modules/packages/ParallelIO.chpl
@@ -144,6 +144,8 @@ module ParallelIO {
       const byteOffsets = try! findDelimChunks(fMeta, delim, tld.size, fileBounds, header);
       coforall (loc, id) in zip(targetLocales, 0..) do on loc {
         const locBounds = byteOffsets[id]..byteOffsets[id+1];
+
+        // if byteOffsets looks like [0, 10, 10, 14, 21], then don't try to read 10..10 (locale 1)
         if locBounds.size > 1 {
           const locFile = try! open(filePath, ioMode.r),
                 locByteOffsets = try! findDelimChunks(locFile, delim, nTasks, locBounds, headerPolicy.noHeader);
@@ -261,6 +263,8 @@ module ParallelIO {
       const byteOffsets = try! findDelimChunks(fMeta, delim, tld.size, fileBounds, header);
       coforall (loc, id) in zip(targetLocales, 0..) do on loc {
         const locBounds = byteOffsets[id]..<byteOffsets[id+1];
+
+        // if byteOffsets looks like [0, 10, 10, 14, 21], then don't try to read 10..10 (locale 1)
         if locBounds.size > 1 {
           const locFile = try! open(filePath, ioMode.r),
                 locByteOffsets = try! findDelimChunks(locFile, delim, nTasks, locBounds, headerPolicy.noHeader);

diff --git a/modules/standard/IO.chpl b/modules/standard/IO.chpl
@@ -7171,6 +7171,8 @@ iter fileReader.lines(
       const byteOffsets = findFileChunks(f, targetLocales.size, myBounds);
       coforall lid in 0..<targetLocales.size do on targetLocales[tld.orderToIndex(lid)] {
         const locBounds = byteOffsets[lid]..byteOffsets[lid+1];
+
+        // if byteOffsets looks like [0, 10, 10, 14, 21], then don't try to read 10..10 (locale 1)
         if locBounds.size > 1 {
           const locFile = try! open(fpath, ioMode.r),
                 nTasks = if dataParTasksPerLocale>0 then dataParTasksPerLocale