Unexpected termination of PM-1

[nordi]

Originally Posted by kruoli

1. Run Prime95/mprime with Pminus1=1,2,{exponent},-1,{B1},0.
2. Now, a save file exists m{zero padded exponent}.
3. Open the file in a Hex Editor.
   1. Remove the first 88 bytes.
   2. Reverse all bytes.
   3. Copy the hexadecimal representation.
   4. Remove leading zeros.
   5. Convert this to lower case.
4. Create a new file with this content:

   METHOD=P-1; B1={B1}; N=2^{exponent}-1; X=0x{modified hex data from the last step}; CHECKSUM=0; PROGRAM=; Y=0x0; X0=0x3; Y0=0x0; WHO=; TIME=;

5. ...

Thanks a LOT! Since I'm lazy, I automated steps II and III with some Python (version 3.6 or higher) code:

# fill in these 3 values:
b1 = 1000000
exponent = 5273
known_factors = [38134337, 10372530354079, 105636369464519254639]

input_file = "m{:07}".format(exponent)
if known_factors:
    known_factors = "/" + "/".join(map(str, known_factors))
else:
    known_factors = ""
with open(input_file, "rb") as f:
    data = reversed(f.read()[88:])

hex_codes = "".join(map("{:02x}".format, data))

line = "METHOD=P-1; B1={}; N=(2^{}-1){}; X=0x{}; CHECKSUM=0; PROGRAM=; Y=0x0; X0=0x3; Y0=0x0; WHO=; TIME=;".format(
        b1, exponent, known_factors, hex_codes
)
print(line)

This even works with known factors: In my test run with M5273 I found the missing 26 digit factor via gmp-ecm.