Document major interface changes to icetSingleImageCompose.

Now accepts and returns sparse images.  Also no longer collects image
pieces.

Changes.txt

-const array for compose_group in single image strategy functions.
-
-icetSingleImageCompose interface change.
-
-icetSingleImageCollect.
-
-General change to single image strategy functions.
-
 ICET_MAGIC_K state variable, CMake variable, and environment variable.
 
 icetCompressedCompressedComposite

src/strategies/common.c

@@ -590,7 +590,7 @@ void icetSendRecvLargeMessages(IceTInt numMessagesSending,
                         bufferSize);
 }
 
-void icetSingleImageCompose(IceTInt *compose_group,
+void icetSingleImageCompose(const IceTInt *compose_group,
                             IceTInt group_size,
                             IceTInt image_dest,
                             IceTSparseImage input_image,

src/strategies/common.h

@@ -160,7 +160,7 @@ void icetSendRecvLargeMessages(IceTInt numMessagesSending,
    piece_offset - The offset to the start of the valid pixels will be placed
         in this argument.
 */
-void icetSingleImageCompose(IceTInt *compose_group,
+void icetSingleImageCompose(const IceTInt *compose_group,
                             IceTInt group_size,
                             IceTInt image_dest,
                             IceTSparseImage input_image,
@@ -173,10 +173,10 @@ void icetSingleImageCompose(IceTInt *compose_group,
    call this function after a call to icetSingleImageCompose to complete the
    image composition.  Unlike icetSingleImageCompose, however, this function
    must be called on all processes, not just those in a group.  Processes that
-   have no piece of the image should pass 0 for both piece_offset and
-   piece_size.
+   have no piece of the image should pass 0 for piece_offset and a null or other
+   zero-size image for input_image.
 
-   input_image - Contains the image composited image partition returned from
+   input_image - Contains the composited image partition returned from
         icetSingleImageCompose.
    dest - The rank of the process to where the image should be collected.  Be
         aware that this is generally a different value than the image_dest

src/strategies/sequential.c

@@ -125,9 +125,9 @@ IceTImage icetSequentialCompose(void)
                 my_image = icetGetStateBufferImage(
                                                   SEQUENTIAL_FINAL_IMAGE_BUFFER,
                                                   tile_width, tile_height);
-                icetDecompressSubImage(composited_image,
-                                       piece_offset,
-                                       my_image);
+                icetDecompressSubImageCorrectBackground(composited_image,
+                                                        piece_offset,
+                                                        my_image);
                 icetStateSetInteger(ICET_VALID_PIXELS_TILE, i);
                 icetStateSetInteger(ICET_VALID_PIXELS_OFFSET, piece_offset);
                 icetStateSetInteger(ICET_VALID_PIXELS_NUM, piece_size);