diff --git a/src/frontend/outitf.c b/src/frontend/outitf.c
index dbbfabac6..e82937ead 100644
--- a/src/frontend/outitf.c
+++ b/src/frontend/outitf.c
@@ -946,6 +946,7 @@ fileStartPoint(FILE *fp, bool bin, int num)
 }
 
 
+/* This code is used when one does  RUN aap.raw  but *not* when doing RUN. */
 static void
 fileAddRealValue(FILE *fp, bool bin, double value)
 {
@@ -1059,6 +1060,8 @@ plotInit(runDesc *run)
     }
 }
 
+/* mhx: minimize the number of REALLOCs */
+#define OUTSIZE (256*4096)
 
 static void
 plotAddRealValue(dataDesc *desc, double value)
@@ -1066,11 +1069,11 @@ plotAddRealValue(dataDesc *desc, double value)
     struct dvec *v = desc->vec;
 
     if (isreal(v)) {
-        v->v_realdata = TREALLOC(double, v->v_realdata, v->v_length + 1);
+        if ((v->v_dims[0] & (OUTSIZE - 1)) == 0) v->v_realdata = TREALLOC(double, v->v_realdata, v->v_length + OUTSIZE);
         v->v_realdata[v->v_length] = value;
     } else {
         /* a real parading as a VF_COMPLEX */
-        v->v_compdata = TREALLOC(ngcomplex_t, v->v_compdata, v->v_length + 1);
+        if ((v->v_dims[0] & (OUTSIZE - 1)) == 0) v->v_compdata = TREALLOC(ngcomplex_t, v->v_compdata, v->v_length + OUTSIZE);
         v->v_compdata[v->v_length].cx_real = value;
         v->v_compdata[v->v_length].cx_imag = 0.0;
     }
@@ -1085,7 +1088,7 @@ plotAddComplexValue(dataDesc *desc, IFcomplex value)
 {
     struct dvec *v = desc->vec;
 
-    v->v_compdata = TREALLOC(ngcomplex_t, v->v_compdata, v->v_length + 1);
+    if ((v->v_dims[0] & (OUTSIZE - 1)) == 0) v->v_compdata = TREALLOC(ngcomplex_t, v->v_compdata, v->v_length + OUTSIZE);
     v->v_compdata[v->v_length].cx_real = value.real;
     v->v_compdata[v->v_length].cx_imag = value.imag;