day 9, pure compute, good candidate for compier:

* python: 2.525    s ±  0.169 s
* pypy:     175.0 ms ±   8.9 ms  14x
* codon:     29.3 ms ±   7.9 ms  87x

d09/part1.py

@@ -0,0 +1,36 @@
+import sys, os
+
+I = list(map(int, sys.stdin.read().strip()))
+
+def sum_n(a, b):
+    return (b-a+1)*(a+b)//2
+
+I = I
+j = 0
+b = 0
+res = 0
+id = len(I)//2  # last ID
+x = I[len(I)-1]
+for i in range(len(I)//2):
+    if len(I)-2*j-1 - 2*i == 0:
+        res += sum_n(b, b+x-1)*i
+        break
+    nb = b + I[2*i]
+    res += sum_n(b, nb-1)*i
+    b = nb
+    space = I[2*i+1]
+    while space > 0:
+        if x > space:
+            nb = b + space
+            res += sum_n(b, nb-1)*id
+            x -= space
+            space = 0
+        else:
+            nb = b + x
+            res += sum_n(b, nb-1)*id
+            id -= 1
+            space -= x
+            j += 1
+            x = I[len(I)-2*j-1]
+        b = nb
+print(res)

d09/part2.py

@@ -0,0 +1,30 @@
+import sys, os
+
+I = list(map(int, sys.stdin.read().strip()))
+
+def sum_n(a, b):
+    return (b-a+1)*(a+b)//2
+
+idxs = []
+b = 0
+for i in I:
+    idxs.append(b)
+    b += i
+
+res = 0
+id = len(I)//2  # last id
+for j in range(len(I)-1,-1,-2):  # backward
+    fsize = I[j]
+    for i in range(1, j, 2):  # find free space forward
+        if I[i] >= fsize: # enough free space
+            b = idxs[i]
+            res += sum_n(b, b+fsize-1)*id
+            idxs[i] += fsize
+            I[i] -= fsize
+            break
+    else:  # block too big stays where it is
+        b = idxs[j]
+        res += sum_n(b, b+fsize-1)*id
+    id -= 1
+
+print(res)