diff --git a/.vscode/launch.json b/.vscode/launch.json
index 34f8f4b..9451ef3 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -13,7 +13,8 @@
             "args": [
                 "mem",
                 "-t",
-                "1",
+                "128",
+                "-K", "800000000",
                 "-M",
                 "-R",
                 "'@RG\\tID:normal\\tSM:normal\\tPL:illumina\\tLB:normal\\tPG:bwa'",
diff --git a/Makefile b/Makefile
index e2a86ae..884a90b 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,7 @@ OPTIMIZE=-O3
 CFLAGS=		-g -Wall -Wno-unused-function $(AVX2) $(AVX512BW) $(OPTIMIZE)
 
 WRAP_MALLOC=-DUSE_MALLOC_WRAPPERS
-#SAM_EXACT= -DSAM_EXACT
+SAM_EXACT= -DSAM_EXACT
 SHOW_PERF= -DSHOW_PERF
 SHOW_DATA_PERF=  -DSHOW_DATA_PERF
 DEBUG_FILE_OUTPUT= -DDEBUG_FILE_OUTPUT
diff --git a/bwa.c b/bwa.c
index 23e3a72..08e5308 100644
--- a/bwa.c
+++ b/bwa.c
@@ -159,7 +159,8 @@ void bseq_read_pe_mt(int chunk_size, int* n_, void* ks1_, void* ks2_, int copy_c
             *m_ = n;
             return;
         }
-        m = (chunk_size + size / init_n_reads - 1) / (size / init_n_reads);
+        float bases_per_read = size * 1.0 / init_n_reads;
+        m = (chunk_size + bases_per_read * 100) / (bases_per_read); // 多开辟100个reads的冗余空间
 #else
         m = 50000;
 #endif