diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
index 9b389ae..af25b4e 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
@@ -12,14 +12,18 @@
 import org.teachfx.antlr4.ep20.parser.CymbolLexer;
 import org.teachfx.antlr4.ep20.parser.CymbolParser;
 import org.teachfx.antlr4.ep20.pass.ast.CymbolASTBuilder;
+import org.teachfx.antlr4.ep20.pass.cfg.CFG;
 import org.teachfx.antlr4.ep20.pass.cfg.ControlFlowAnalysis;
 import org.teachfx.antlr4.ep20.pass.codegen.CymbolAssembler;
 import org.teachfx.antlr4.ep20.pass.ir.CymbolIRBuilder;
 import org.teachfx.antlr4.ep20.pass.symtab.LocalDefine;
+import org.teachfx.antlr4.ep20.utils.StreamUtils;
 
 import java.io.*;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
 
 public class Compiler {
 
@@ -44,7 +48,8 @@ public static void main(String[] args) throws IOException {
         CommonTokenStream tokenStream = new CommonTokenStream(lexer);
         CymbolParser parser = new CymbolParser(tokenStream);
         ParseTree parseTree = parser.file();
-        CymbolASTBuilder astBuilder = new CymbolASTBuilder("t.cymbol");
+
+        CymbolASTBuilder astBuilder = new CymbolASTBuilder();
         ASTNode astRoot = parseTree.accept(astBuilder);
         astRoot.accept(new LocalDefine());
         var irBuilder = new CymbolIRBuilder();
@@ -52,20 +57,18 @@ public static void main(String[] args) throws IOException {
         astRoot.accept(irBuilder);
 
         irBuilder.prog.optimizeBasicBlock();
-        var cfgOptimizer = new ControlFlowAnalysis<IRNode>();
-        var cnt = 0;
-        var codeBuffer = new LinkedList<IRNode>();
-
-        for(var funBlock : irBuilder.prog.blockList) {
-            var cfg = irBuilder.getCFG(funBlock);
-            saveToEp20Res(cfg.toString(),"origin"+cnt);
-            cfg.addOptimizer(cfgOptimizer);
-            cfg.applyOptimizers();
-            saveToEp20Res(cfg.toString(),"optimized"+cnt);
-            cnt++;
-            logger.info("CFG:\n" + cfg.toString());
-            codeBuffer.addAll(cfg.getIRNodes());
-        }
+
+        var codeBuffer = StreamUtils.indexStream(irBuilder.prog.blockList.stream()
+                        .map(irBuilder::getCFG))
+                .peek(cfgPair -> {
+                    var cfg = cfgPair.getRight();
+                    var idx = cfgPair.getLeft();
+                    saveToEp20Res(cfg.toString(), "%d_origin".formatted(idx));
+                    cfg.addOptimizer(new ControlFlowAnalysis<>());
+                    cfg.applyOptimizers();
+                    saveToEp20Res(cfg.toString(), "%d_optimized".formatted(idx));
+                })
+                .flatMap(s -> s.getRight().getIRNodes().stream()).toList();
 
         var assembler = new CymbolAssembler();
         assembler.visit(codeBuffer);
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/ast/CompileUnit.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/ast/CompileUnit.java
index 91e8036..ff57e71 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/ast/CompileUnit.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/ast/CompileUnit.java
@@ -9,7 +9,6 @@
 import java.util.List;
 
 public class CompileUnit extends ASTNode {
-    private String srcName;
 
     public void addFuncDecl(FuncDeclNode funcDecl) {
         this.funcDeclarations.add(funcDecl);
@@ -29,9 +28,7 @@ public CompileUnit(List<VarDeclNode> varDeclarations, List<FuncDeclNode> funcDec
         this.ctx = ctx;
     }
 
-    public CompileUnit(String srcName) {
-        this.srcName = srcName;
-    }
+    public CompileUnit() {}
 
     public List<VarDeclNode> getVarDeclarations() {
         return varDeclarations;
@@ -56,14 +53,6 @@ protected void _dump(Dumper d) {
         d.printNodeList("funcDecl",funcDeclarations);
     }
 
-    public String getSrcName() {
-        return srcName;
-    }
-
-    public void setSrcName(String srcName) {
-        this.srcName = srcName;
-    }
-
     @Override
     public void accept(ASTVisitor visitor) {
         visitor.visit(this);
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ast/CymbolASTBuilder.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ast/CymbolASTBuilder.java
index d3b4044..4106e42 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ast/CymbolASTBuilder.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ast/CymbolASTBuilder.java
@@ -21,15 +21,13 @@
 
 public class CymbolASTBuilder extends CymbolBaseVisitor<ASTNode> implements CymbolVisitor<ASTNode> {
 
-    protected String srcName;
-    public CymbolASTBuilder(String srcName) {
+    public CymbolASTBuilder() {
         super();
-        this.srcName = srcName;
     }
 
     @Override
     public ASTNode visitCompilationUnit(CymbolParser.CompilationUnitContext ctx) {
-        var compilationUnit = new CompileUnit(srcName);
+        var compilationUnit = new CompileUnit();
         for(var childNode : ctx.children) {
             var node = visit(childNode);
             if(node instanceof VarDeclNode varDeclNode) {
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/StreamUtils.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/StreamUtils.java
index d72c429..c7b8137 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/StreamUtils.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/StreamUtils.java
@@ -8,11 +8,20 @@
 import java.util.stream.Stream;
 
 public class StreamUtils {
-    public static <T> int indexOf(Stream<T> stream, Predicate<T> predicate) {
+    public static <T> Stream<? super Pair<Integer, T>> mapWithIndex(Stream<T> stream,Function<? super Pair<Integer, T>,? super Pair<Integer, T>> mapper) {
+        AtomicInteger cnt = new AtomicInteger();
+        return stream.map(s -> Pair.of( cnt.getAndIncrement(),s)).map(mapper);
+    }
+
+    public static <T> Stream<Pair<Integer,T>> indexStream(Stream<T> stream) {
         AtomicInteger cnt = new AtomicInteger();
-        return stream.map(s -> Pair.of(s, cnt.getAndIncrement())).filter(tIntegerPair ->
-            predicate.test(tIntegerPair.getLeft())
-        ).findFirst().map(Pair::getRight).orElse(-1);
+        return stream.map(s -> Pair.of(cnt.getAndIncrement(),s));
+    }
+
+    public static <T> int indexOf(Stream<T> stream, Predicate<T> predicate) {
+       return (int) StreamUtils.indexStream(stream).filter(tIntegerPair ->
+            predicate.test(tIntegerPair.getRight())
+        ).findFirst().map(Pair::getLeft).orElse(-1);
     }
     // find matched object
     public static <T> T find(Stream<T> stream, Predicate<T> predicate) {
diff --git a/ep20/src/main/resources/graph_optimized0.md b/ep20/src/main/resources/graph_0_optimized.md
similarity index 100%
rename from ep20/src/main/resources/graph_optimized0.md
rename to ep20/src/main/resources/graph_0_optimized.md
diff --git a/ep20/src/main/resources/graph_origin0.md b/ep20/src/main/resources/graph_0_origin.md
similarity index 100%
rename from ep20/src/main/resources/graph_origin0.md
rename to ep20/src/main/resources/graph_0_origin.md
diff --git a/ep20/src/main/resources/graph_optimized1.md b/ep20/src/main/resources/graph_1_optimized.md
similarity index 100%
rename from ep20/src/main/resources/graph_optimized1.md
rename to ep20/src/main/resources/graph_1_optimized.md
diff --git a/ep20/src/main/resources/graph_origin1.md b/ep20/src/main/resources/graph_1_origin.md
similarity index 100%
rename from ep20/src/main/resources/graph_origin1.md
rename to ep20/src/main/resources/graph_1_origin.md