BUG: Correct loop order in MT19937 jump

Use the original loop order instead of an inverted order

closes #15394

2 files changed, 9 insertions, 3 deletions

diff --git a/numpy/random/src/mt19937/mt19937-jump.c b/numpy/random/src/mt19937/mt19937-jump.c
index 46b28cf96..de8969bf9 100644
--- a/numpy/random/src/mt19937/mt19937-jump.c
+++ b/numpy/random/src/mt19937/mt19937-jump.c
@@ -187,11 +187,9 @@ void mt19937_jump_state(mt19937_state *state, const char *jump_str) {
   pf = (unsigned long *)calloc(P_SIZE, sizeof(unsigned long));
 
   for (i = MEXP - 1; i > -1; i--) {
-    if (jump_str[i] == '1')
+    if (jump_str[(MEXP - 1) - i] == '1')
       set_coef(pf, i, 1);
   }
-  /* TODO: Should generate the next set and start from 0, but doesn't matter ??
-   */
   if (state->pos >= N) {
     state->pos = 0;
   }
diff --git a/numpy/random/src/mt19937/mt19937-poly.h b/numpy/random/src/mt19937/mt19937-poly.h
index b03747881..016b4f626 100644
--- a/numpy/random/src/mt19937/mt19937-poly.h
+++ b/numpy/random/src/mt19937/mt19937-poly.h
@@ -1,3 +1,11 @@
+/*
+ * 2**128 step polynomial produced using the file mt19937-generate-jump-poly.c
+ * (randomgen) which is a modified version of minipoly_mt19937.c as distributed
+ * in http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/JUMP/jump_ahead_1.02.tar.gz
+ *
+ * These files are not part of NumPy.
+ */
+
 static const char * poly =
 "0001000111110111011100100010101111000000010100100101000001110111100010101000110100101001011001010"
 "1110101101100101011100101101011001110011100011110100001000001011100101100010100000010011101110011"