Did some checks, findings are that pool has issued new difficulty(increased) after 2 submitted shares, but the miner has not yet processed it, sending another work in 3 seconds after the 2nd. Making it fail again newly anticipated difficulty at stratum server side.
We could confirm if you would be able to run the same miner in debug more, so it prints communication messages(must be JSON format).
And also send a bit of logged events after the Low difficulty share error. (e.g. I assume the next log should be about new stratum difficulty arriving from server)
Vardiff will change the difficulty based on the share rate. If that occurs the problem goes away. The problem only occurs on lyra2z with stratum diff 6. You can see in
the logs below the mining.set_difficulty specifies 6 but the web page says 6.4. Anything submitted between 6 & 6.4 is rejected. I've seen it with another
algo but I can't recall which one but it was a different difficulty. The problem is rare because it seems to only occur at one difficulty for each affected
algo. I don't know if any more than 2 algos are affected. You also need a hash rate that will cause vardiff to choose the difficulty that has the
problem.
It looks like 6 is the lowest diff for lyra2z, maybe the lowest diff doesn't match in the pool. I let it run for 20 minutes, one more reject, stratum
diff never changed.
./cpuminer -a lyra2z -o stratum+tcp://mine.zergpool.com:4553 -u XXX -p c27,c=btc,sd=1 -D -P
********** cpuminer-opt 3.19.9 ***********
A CPU miner with multi algo support and optimized for CPUs
with AVX512, SHA and VAES extensions by JayDDee.
BTC donation address: 12tdvfF7KmAsihBXQXynT6E6th2c2pByTT
CPU: Intel(R) Core(TM) i9-9940X CPU @ 3.30GHz
SW built on Jul 12 2022 with GCC 9.3.0
CPU features: AVX512 AES
SW features: AVX512 AES
Algo features: AVX512
Starting miner with AVX512...
[2022-07-17 02:55:59] CPU affinity [!!!!!!!!!!!!!!!!!!!!!!!!!!!!]
[2022-07-17 02:55:59] Creating stratum thread
[2022-07-17 02:55:59] Stratum connect stratum+tcp://mine.zergpool.com:4553
[2022-07-17 02:55:59] Threads restarted for new work.
[2022-07-17 02:55:59] Default miner thread priority 0 (nice 19)
* Trying 103.249.70.7:4553...
* TCP_NODELAY set
* Connected to mine.zergpool.com (103.249.70.7) port 4553 (#0)
* Connection #0 to host mine.zergpool.com left intact
[2022-07-17 02:55:59] > {"id": 1, "method": "mining.subscribe", "params": ["cpuminer-opt/3.19.9"]}
[2022-07-17 02:55:59] < {"id":1,"result":[[["mining.set_difficulty","64"],["mining.notify","16a6524c2c668b573c65f6a15f0343c3"]],"8101adb2",4],"error":null}
[2022-07-17 02:55:59] Stratum session id: 16a6524c2c668b573c65f6a15f0343c3
[2022-07-17 02:55:59] Stratum extranonce1 0x8101adb2, extranonce2 size 4
[2022-07-17 02:55:59] > {"id": 2, "method": "mining.authorize", "params": ["XXX", "X"]}
[2022-07-17 02:55:59] < {"id":2,"result":true,"error":null}
[2022-07-17 02:55:59] > {"id": 3, "method": "mining.extranonce.subscribe", "params": []}
[2022-07-17 02:56:00] < {"id":null,"method":"mining.set_difficulty","params":[6]}
[2022-07-17 02:56:00] Stratum connection established
[2022-07-17 02:56:00] < {"id":null,"method":"mining.notify","params":["31672","7210f86e98886f2ad5af03c27207f9d129c41cba4d4c6ba333169d0ec96cc14a","02000000010000000000000000000000000000000000000000000000000000000000000000ffffffff1f03c64c0d0475b2d36208","7a657267706f6f6c2e636f6d0000000000020000000000000000266a24aa21a9ede2f61c3f71d1defd3fa999dfa36953755c690689799962b48bebd836974e8cf900f902950000000017a91459dd91ee761d256af824aba2229aaa94a3d7b8f58700000000",[],"60000000","1b5bb148","62d3b264",true]}
[2022-07-17 02:56:00] CPU temp: curr 40 C max 0, Freq: 1.200/1.509 GHz
[2022-07-17 02:56:00] Threads restarted for new work.
[2022-07-17 02:56:00] New Stratum Diff 6, Block 871622, Job 31672
Diff: Net 714.73, Stratum 6, Target 0.023438
TTF @ 560.00 h/s: Block 173y173d, Share 2d01h
[2022-07-17 02:56:00] < {"id":3,"result":true,"error":null}
[2022-07-17 02:56:00] < {"id":null,"method":"mining.notify","params":["31674","8ff5b9bdb44be5d111d517f3cb9c66210eb05e14a1b0e5f95a19b918b089d3e4","02000000010000000000000000000000000000000000000000000000000000000000000000ffffffff1f03664c25047db2d36208","7a657267706f6f6c2e636f6d000000000001c0496e0a000000001976a91490df51a56fd5a9fbe7ea3512de486c77c124b57688ac00000000",[],"20000000","1c2142c6","62d3b26c",true]}
[2022-07-17 02:56:00] Threads restarted for new work.
[2022-07-17 02:56:00] New Block 2444390, Net diff 7.6966, Job 31674
Diff: Net 7.6966, Stratum 6, Target 0.023438
TTF @ 560.00 h/s: Block 1y1d, Share 2d01h
[2022-07-17 02:56:17] < {"id":null,"method":"mining.notify","params":["31676","6afe57fc8493efe1cc421b15e2cfaab91ddee8b2347ae3810ac159b7564cdc5e","02000000010000000000000000000000000000000000000000000000000000000000000000ffffffff1f03674c250491b2d36208","7a657267706f6f6c2e636f6d000000000001c0496e0a000000001976a91490df51a56fd5a9fbe7ea3512de486c77c124b57688ac00000000",[],"20000000","1c2147ce","62d3b280",true]}
[2022-07-17 02:56:17] Threads restarted for new work.
[2022-07-17 02:56:17] New Block 2444391, Net diff 7.6921, Job 31676
Diff: Net 7.6921, Stratum 6, Target 0.023438
TTF @ 4234.74 kh/s: Block 2h10m, Share 0m23s
[2022-07-17 02:56:18] 1 Submitted Diff 0.097783, Block 2444391, Job 31676
[2022-07-17 02:56:18] > {"method": "mining.submit", "params": ["XXX", "31676", "00000000", "62d3b280", "56eb4b52"], "id":4}
[2022-07-17 02:56:18] Thread 9, Nonce 524beb56, Xnonce2 00000000
[2022-07-17 02:56:18] Data[0:19]: 00000020 fc57fe6a e1ef9384 151b42cc b9aacfe2 b2e8de1d 81e37a34 b759c10a 5edc4c56 822f7b06
[2022-07-17 02:56:18] : c50cbcd9 ffc202b2 ff05298f e0e05a5a 43c98498 2ba8c440 d634cd75 80b2d362 ce47211c 524beb56
[2022-07-17 02:56:18] Hash[7:0]: 0000000a 3a0d1ef1 d767f69a c51fb4fb cdee6a46 244caedf 33e90ce9 a706f2eb
[2022-07-17 02:56:18] Targ[7:0]: 0000002a aaaaaaaa aaaa0000 00000000 ffffffff ffffffff ffffffff ffffffff
[2022-07-17 02:56:18] < {"id":4,"result":true,"error":null}
[2022-07-17 02:56:18] 1 Accepted 1 S0 R0 B0, 19.309 sec (166ms)
Diff 0.097783, Block 2444391, Job 31676
[2022-07-17 02:56:55] < {"id":null,"method":"mining.notify","params":["31677","231d9a1408114d11262e9cdd2d40e167384310e1d7f013eeffdc0277fb6c1a97","02000000010000000000000000000000000000000000000000000000000000000000000000ffffffff1f03684c2504b7b2d36208","7a657267706f6f6c2e636f6d000000000001c0496e0a000000001976a91490df51a56fd5a9fbe7ea3512de486c77c124b57688ac00000000",[],"20000000","1c21491c","62d3b2a6",true]}
[2022-07-17 02:56:55] Threads restarted for new work.
[2022-07-17 02:56:55] New Block 2444392, Net diff 7.6909, Job 31677
Diff: Net 7.6909, Stratum 6, Target 0.023438
TTF @ 4473.65 kh/s: Block 2h03m, Share 0m22s
[2022-07-17 02:57:10] > {"method": "mining.submit", "params": ["XXX", "31677", "00000000", "62d3b2a6", "a2346f12"], "id":4}
[2022-07-17 02:57:10] 2 Submitted Diff 0.024655, Block 2444392, Job 31677
[2022-07-17 02:57:10] Thread 2, Nonce 126f34a2, Xnonce2 00000000
[2022-07-17 02:57:10] Data[0:19]: 00000020 149a1d23 114d1108 dd9c2e26 67e1402d e1104338 ee13f0d7 7702dcff 971a6cfb ffc9a71a
[2022-07-17 02:57:10] : daa10652 8fda9673 454daeb4 85c82321 cbe29727 4fd90a69 45ba4d67 a6b2d362 1c49211c 126f34a2
[2022-07-17 02:57:10] Hash[7:0]: 00000028 8f1a0b53 00a8cb64 5560440f 7ba90cbe 5cfe280c 3d90646b fe49ecf7
[2022-07-17 02:57:10] Targ[7:0]: 0000002a aaaaaaaa aaaa0000 00000000 ffffffff ffffffff ffffffff ffffffff
[2022-07-17 02:57:10] < {"id":4,"result":false,"error":[26,"Low difficulty share",null]}
[2022-07-17 02:57:10] 2 A1 S0 Rejected 1 B0, 52.211 sec (164ms)
Diff 0.024655, Block 2444392, Job 31677
[2022-07-17 02:57:10] Reject reason: Low difficulty share
Hash: 000000288f1a0b5300aa000000000000ffffffffffffffff
Target: 0000002aaaaaaaaaaaaa000000000000ffffffffffffffff
[2022-07-17 02:57:14] > {"method": "mining.submit", "params": ["XXX", "31677", "00000000", "62d3b2a6", "15972f80"], "id":4}
[2022-07-17 02:57:14] 3 Submitted Diff 0.039369, Block 2444392, Job 31677
[2022-07-17 02:57:14] Thread 14, Nonce 802f9715, Xnonce2 00000000
[2022-07-17 02:57:14] Data[0:19]: 00000020 149a1d23 114d1108 dd9c2e26 67e1402d e1104338 ee13f0d7 7702dcff 971a6cfb ffc9a71a
[2022-07-17 02:57:14] : daa10652 8fda9673 454daeb4 85c82321 cbe29727 4fd90a69 45ba4d67 a6b2d362 1c49211c 802f9715
[2022-07-17 02:57:14] Hash[7:0]: 00000019 669e5188 dc9b1ce3 445a5404 c26590b4 fcbd197e 12918b98 1ef90dee
[2022-07-17 02:57:14] Targ[7:0]: 0000002a aaaaaaaa aaaa0000 00000000 ffffffff ffffffff ffffffff ffffffff
[2022-07-17 02:57:14] < {"id":4,"result":true,"error":null}
[2022-07-17 02:57:14] 3 Accepted 2 S0 R1 B0, 3.941 sec (164ms)
Diff 0.039369, Block 2444392, Job 31677
[2022-07-17 02:57:27] > {"method": "mining.submit", "params": ["1FXaRoufZC6LyPzjNrs7wS47tpgzEpBSiw", "31677", "00000000", "62d3b2a6", "f9f14dc0"], "id":4}
