PERF: only store the needed suffix arrays in mem

Might help a bit with memory usage

wotplot/_make.py

@@ -310,11 +310,6 @@ def _mlog(s):
     _mlog("computing suffix array for s2...")
     s2_sa = _get_suffix_array(s2)
 
-    _mlog("computing ReverseComplement(s2)...")
-    rcs2 = rc(s2)
-    _mlog("computing suffix array for ReverseComplement(s2)...")
-    rcs2_sa = _get_suffix_array(rcs2)
-
     # Find k-mers that are shared between both strings (not considering
     # reverse-complementing)
     matches = {}
@@ -323,6 +318,15 @@ def _mlog(s):
         s1, s2, k, s1_sa, s2_sa, matches, yorder=yorder, binary=binary
     )
     _mlog(f"found {len(matches):,} forward match cell(s).")
+    # I'm not sure if this is needed, but we might as well be very clear that
+    # "hey this big chunky suffix array is now unnecessary please garbage
+    # collect it"
+    del s2_sa
+
+    _mlog("computing ReverseComplement(s2)...")
+    rcs2 = rc(s2)
+    _mlog("computing suffix array for ReverseComplement(s2)...")
+    rcs2_sa = _get_suffix_array(rcs2)
 
     _mlog("finding matches between s1 and ReverseComplement(s2)...")
     _fill_match_cells(
@@ -337,6 +341,7 @@ def _mlog(s):
         s2isrc=True,
     )
     _mlog(f"found {len(matches):,} total match cell(s).")
+    del rcs2_sa
     density = 100 * (len(matches) / (mat_shape[0] * mat_shape[1]))
     _mlog(f"density = {density:.2f}%.")