make arrayjoin much faster with large arrays

jcupitt · jcupitt · commit feae09e9cdc0 · 2022-12-29T20:50:22.000Z
arrayjoin was making a region on every input image during startup, and repeating for each thread (!!) so large arrays could be very expensive to join. Instead, make input regions on demand, and computre set of required input images rather than searching for them. See libvips#3247
diff --git a/ChangeLog b/ChangeLog
@@ -28,6 +28,7 @@
 - deprecate gifsave `reoptimise`, add `reuse`
 - add `encoder` to heifsave [dloebl]
 - add `cplusplus` meson build option [jcupitt]
+- make arrayjoin much faster with large arrays
 
 9/11/22 started 8.13.4
 - missing include in mosaic_fuzzer [ServOKio]
diff --git a/libvips/conversion/arrayjoin.c b/libvips/conversion/arrayjoin.c
@@ -4,6 +4,8 @@
  * 	- from join.c
  * 6/9/21
  * 	- minmise inputs once we've used them
+ * 29/12/22
+ *	- much faster with large arrays
  */
 
 /*
@@ -80,43 +82,67 @@ static int
 vips_arrayjoin_gen( VipsRegion *or, void *seq, 
 	void *a, void *b, gboolean *stop )
 {
-	VipsRegion **ir = (VipsRegion **) seq;
+	VipsImage **in = (VipsImage **) a;
 	VipsArrayjoin *join = (VipsArrayjoin *) b;
 	VipsConversion *conversion = VIPS_CONVERSION( join );
 	VipsRect *r = &or->valid;
-
 	int n;
-	VipsImage **in;
+
+	/* Find the left/top/width/height of the cells this region touches.
+	 */
+	int cell_width = join->hspacing + join->shim;
+	int cell_height = join->vspacing + join->shim;
+	int left = r->left / cell_width;
+	int top = r->top / cell_height;
+	int width = (VIPS_ROUND_UP( VIPS_RECT_RIGHT( r ), cell_width ) - 
+		VIPS_ROUND_DOWN( r->left, cell_width )) / cell_width;
+	int height = (VIPS_ROUND_UP( VIPS_RECT_BOTTOM( r ), cell_height ) - 
+		VIPS_ROUND_DOWN( r->top, cell_height )) / cell_height;
+
 	int i;
-	gboolean just_one;
+	VipsRegion *reg;
 
-	in = vips_array_image_get( join->in, &n );
+	/* Size of image array.
+	 */
+	vips_array_image_get( join->in, &n );
 
-	/* Does this rect fit completely within one of our inputs? 
+	/* Does this rect fit completely within one of our inputs? We can just
+	 * forward the request.
 	 */
-	just_one = FALSE;
-	for( i = 0; i < n; i++ ) 
-		if( vips_rect_includesrect( &join->rects[i], r ) ) {
-			just_one = TRUE;
-			break;
+	if( width == 1 && height == 1 ) {
+		i = VIPS_MIN( n - 1, left + top * join->across );
+
+		reg = vips_region_new( in[i] );
+
+		if( vips__insert_just_one( or, reg,
+			join->rects[i].left, join->rects[i].top ) ) {
+			g_object_unref( reg );
+			return( -1 );
 		}
 
-	if( just_one ) {
-		/* Just needs one input, we can forward the request to that
-		 * region.
-		 */
-		if( vips__insert_just_one( or, ir[i],
-			join->rects[i].left, join->rects[i].top ) )
-		       return( -1 );
+		g_object_unref( reg );
 	}
 	else {
 		/* Output requires more than one input. Paste all touching 
 		 * inputs into the output.
 		 */
-		for( i = 0; i < n; i++ ) 
-			if( vips__insert_paste_region( or, ir[i], 
-				&join->rects[i] ) )
-				return( -1 );
+		int x, y;
+
+		for( y = 0; y < height; y++ )
+			for( x = 0; x < width; x++ ) {
+				i = VIPS_MIN( n - 1,
+					x + left + (y + top) * join->across );
+
+				reg = vips_region_new( in[i] );
+
+				if( vips__insert_paste_region( or, reg, 
+					&join->rects[i] ) ) {
+					g_object_unref( reg );
+					return( -1 );
+				}
+
+				g_object_unref( reg );
+			}
 	}
 
 	if( vips_image_is_sequential( conversion->out ) )
@@ -320,9 +346,12 @@ vips_arrayjoin_build( VipsObject *object )
 	conversion->out->Xsize = output_width;
 	conversion->out->Ysize = output_height;
 
+	/* DOn't use start_many -- the set of input images can be huge (many
+	 * 10s of 1000s) and we don't want to have 20,000 regions active. It's
+	 * much quicker to make them on demand.
+	 */
 	if( vips_image_generate( conversion->out,
-		vips_start_many, vips_arrayjoin_gen, vips_stop_many, 
-		size, join ) )
+		NULL, vips_arrayjoin_gen, NULL, size, join ) )
 		return( -1 );
 
 	return( 0 );
diff --git a/libvips/iofuncs/region.c b/libvips/iofuncs/region.c
@@ -1621,8 +1621,7 @@ vips_region_generate( VipsRegion *reg, void *a )
  * Use vips_sink_screen() to calculate an area of pixels in the 
  * background.
  *
- * See also: vips_sink_screen(), 
- * vips_region_prepare_to().
+ * See also: vips_sink_screen(), vips_region_prepare_to().
  *
  * Returns: 0 on success, or -1 on error.
  */

Original file line number	Diff line number	Diff line change
`@@ -1621,8 +1621,7 @@ vips_region_generate( VipsRegion reg, void a )`
`1621`	`1621`	`* Use vips_sink_screen() to calculate an area of pixels in the`
`1622`	`1622`	`* background.`
`1623`	`1623`	`*`
`1624`		`- * See also: vips_sink_screen(),`
`1625`		`- * vips_region_prepare_to().`
	`1624`	`+ * See also: vips_sink_screen(), vips_region_prepare_to().`
`1626`	`1625`	`*`
`1627`	`1626`	`* Returns: 0 on success, or -1 on error.`
`1628`	`1627`	`*/`