Simplification: don't copy identity ops

hinerm · hinerm · commit 1171aef5e7b6 · 2024-03-06T08:45:42.000-06:00
If during simplification the output/mutable input ops are identity
ops, then we do not need a copy op to move data between them.
diff --git a/scijava-ops-engine/src/main/java/org/scijava/ops/engine/matcher/simplify/SimplificationUtils.java b/scijava-ops-engine/src/main/java/org/scijava/ops/engine/matcher/simplify/SimplificationUtils.java
@@ -228,31 +228,32 @@ public static SimplifiedOpInfo simplifyInfo(OpEnvironment env, OpInfo info) {
 	) {
 		int ioIndex = SimplificationUtils.findMutableArgIndex(Types.raw(info
 			.opType()));
-		// If IO index is -1, output is returned - no need to copy.
-		if (ioIndex == -1) {
-			return null;
+		if (ioIndex > -1 && !(isIdentity(inFocusers.get(ioIndex)) && isIdentity(outSimplifier))) {
+			// Otherwise, we need an Op to convert the simple output back into the
+			// pre-focused input
+			// Determine simple output type.
+			var simpleOut = outType(info.outputType(), outSimplifier);
+			// Determine unfocused input type.
+			var focuserInfo = Ops.info(inFocusers.get(ioIndex));
+			Map<TypeVariable<?>, Type> typeAssigns = new HashMap<>();
+			GenericAssignability.inferTypeVariables( //
+					new Type[] { focuserInfo.outputType() }, //
+					new Type[] { info.inputTypes().get(ioIndex) }, //
+					typeAssigns //
+			);
+			var unfocusedInput = Nil.of(Types.mapVarToTypes( //
+					focuserInfo.inputTypes().get(0), //
+					typeAssigns //
+			));
+			// Match a copier
+			return Ops.rich(env.unary("engine.copy", h) //
+					.inType(simpleOut) //
+					.outType(unfocusedInput) //
+					.computer());
 		}
-		// Otherwise, we need an Op to convert the simple output back into the
-		// pre-focused input
-		// Determine simple output type.
-		var simpleOut = outType(info.outputType(), outSimplifier);
-		// Determine unfocused input type.
-		var focuserInfo = Ops.info(inFocusers.get(ioIndex));
-		Map<TypeVariable<?>, Type> typeAssigns = new HashMap<>();
-		GenericAssignability.inferTypeVariables( //
-			new Type[] { focuserInfo.outputType() }, //
-			new Type[] { info.inputTypes().get(ioIndex) }, //
-			typeAssigns //
-		);
-		var unfocusedInput = Nil.of(Types.mapVarToTypes( //
-			focuserInfo.inputTypes().get(0), //
-			typeAssigns //
-		));
-		// Match a copier
-		return Ops.rich(env.unary("engine.copy", h) //
-			.inType(simpleOut) //
-			.outType(unfocusedInput) //
-			.computer());
+		// No mutable parameter and/or pathway is an identity pathway, so no copy
+		// op necessary
+		return null;
 	}
 
 	/**
diff --git a/scijava-ops-engine/src/main/java/org/scijava/ops/engine/matcher/simplify/SimplifiedOpRequest.java b/scijava-ops-engine/src/main/java/org/scijava/ops/engine/matcher/simplify/SimplifiedOpRequest.java
@@ -52,6 +52,8 @@
 import org.scijava.types.Types;
 import org.scijava.types.inference.GenericAssignability;
 
+import static org.scijava.ops.engine.matcher.simplify.SimplificationUtils.isIdentity;
+
 public class SimplifiedOpRequest implements OpRequest {
 
 	/** Name of the op, or null for any name. */
@@ -104,8 +106,12 @@ public SimplifiedOpRequest(OpRequest req, OpEnvironment env) {
 		type = SimplificationUtils.retypeOpType(req.getType(), inTypes, outType);
 		// TODO: Fix
 		int mutableIndex = SimplificationUtils.findMutableArgIndex(Types.raw(type));
-		this.outputCopier = mutableIndex == -1 ? null : simplifierCopyOp(env, req
-			.getArgs()[mutableIndex]);
+		if (mutableIndex >= 0 && !(isIdentity(inSimplifiers.get(mutableIndex))
+				&& isIdentity(outFocuser))) {
+			this.outputCopier = simplifierCopyOp(env, req.getArgs()[mutableIndex]);
+		} else {
+			this.outputCopier = null;
+		}
 	}
 
 	private Type[] simpleArgs(Type[] args, List<RichOp<Function<?, ?>>> ops) {
