GraphicsMagick: ReadPNMImage(): Compute the number of threads to...

changeset c2f340f17279 in /hg/GraphicsMagick
details: http://hg.GraphicsMagick.org/hg/GraphicsMagick?cmd=changeset;node=c2f340f17279
summary: ReadPNMImage(): Compute the number of threads to use.

diffstat:

 ChangeLog          |   3 +++
 coders/pnm.c       |  27 ++++++++++++++++++++++-----
 www/Changelog.html |   2 ++
 3 files changed, 27 insertions(+), 5 deletions(-)

diffs (77 lines):

diff -r 5b5f8e90be72 -r c2f340f17279 ChangeLog
--- a/ChangeLog	Thu Dec 29 13:14:51 2022 -0600
+++ b/ChangeLog	Thu Dec 29 14:17:51 2022 -0600
@@ -1,5 +1,8 @@
 2022-12-29  Bob Friesenhahn  <[email protected]>
 
+	* coders/pnm.c (ReadPNMImage): Compute the number of threads to
+	use.
+
 	* NEWS.txt: Update the news.
 
 	* magick/command.c: Add use of GetFirstImageInList() where needed
diff -r 5b5f8e90be72 -r c2f340f17279 coders/pnm.c
--- a/coders/pnm.c	Thu Dec 29 13:14:51 2022 -0600
+++ b/coders/pnm.c	Thu Dec 29 14:17:51 2022 -0600
@@ -268,10 +268,20 @@
     XV_332_Format /* P7 332 */
   } PNMSubformat;
 
-#if defined(HAVE_OPENMP) && !defined(DisableSlowOpenMP)
+#if defined(HAVE_OPENMP)
 #  define PNMReadUseOpenMP 1
-#  define PNMReadThreads (Min(2,omp_get_max_threads()))
-#endif
+
+static int PNMReadThreads(const Image* image, const size_t bytes_per_row)
+{
+  const int omp_max_threads = omp_get_max_threads();
+  long threads;
+  ARG_NOT_USED(image);
+  threads=(Min(bytes_per_row/4096UL,(unsigned long) omp_max_threads));
+  if (0 == threads)
+    threads=1;
+  return (int) threads;
+}
+#endif /* defined(HAVE_OPENMP) */
 
 static Image *ReadPNMImage(const ImageInfo *image_info,ExceptionInfo *exception)
 {
@@ -868,9 +878,9 @@
             unsigned int
               sample_max;
 
-#if defined(HAVE_OPENMP) && !defined(DisableSlowOpenMP)
+#if defined(HAVE_OPENMP)
             int
-              pnm_read_threads = PNMReadThreads;
+              pnm_read_threads;
 #endif
 
             (void) LogMagickEvent(CoderEvent,GetMagickModule(),"Reading PAM");
@@ -1017,6 +1027,13 @@
                   }
               }
 
+#if defined(HAVE_OPENMP)
+            pnm_read_threads = PNMReadThreads(image,bytes_per_row);
+            if (image->logging)
+              (void) LogMagickEvent(CoderEvent,GetMagickModule(),
+                                    "Using %d thread%s...", pnm_read_threads,
+                                    pnm_read_threads > 1 ? "s" : "");
+#endif
             scanline_set=AllocateThreadViewDataArray(image,exception,bytes_per_row,1);
             if (scanline_set == (ThreadViewDataSet *) NULL)
               ThrowReaderException(ResourceLimitError,MemoryAllocationFailed,image);
diff -r 5b5f8e90be72 -r c2f340f17279 www/Changelog.html
--- a/www/Changelog.html	Thu Dec 29 13:14:51 2022 -0600
+++ b/www/Changelog.html	Thu Dec 29 14:17:51 2022 -0600
@@ -40,6 +40,8 @@
 <p>2022-12-29  Bob Friesenhahn  &lt;<a class="reference external" href="mailto:bfriesen&#37;&#52;&#48;simple&#46;dallas&#46;tx&#46;us">bfriesen<span>&#64;</span>simple<span>&#46;</span>dallas<span>&#46;</span>tx<span>&#46;</span>us</a>&gt;</p>
 <blockquote>
 <ul class="simple">
+<li><p>coders/pnm.c (ReadPNMImage): Compute the number of threads to
+use.</p></li>
 <li><p>NEWS.txt: Update the news.</p></li>
 <li><p>magick/command.c: Add use of GetFirstImageInList() where needed
 to assure that the list pointer is to the first image.</p></li>