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digitalmars.D.learn - Why is this happening to my software? An illegal instruction error.

reply Murilo <murilomiranda92 hotmail.com> writes:
I've created a software which performs the Fermat's Primality 
Test, however if I input a very big number it causes an error 
saying "Illegal instruction (core dumped)". Does anyone know why?

I've used GDB and here is the message:
Program received signal SIGILL, Illegal instruction.
0x00005555555e40b0 in 
_D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()

Here is the link to the source code: 
https://github.com/MuriloMir/Fermat-primality-test
Jun 18
next sibling parent reply "H. S. Teoh" <hsteoh qfbox.info> writes:
On Tue, Jun 18, 2024 at 11:07:47PM +0000, Murilo via Digitalmars-d-learn wrote:

 I've created a software which performs the Fermat's Primality Test,
 however if I input a very big number it causes an error saying
 "Illegal instruction (core dumped)". Does anyone know why?
 
 I've used GDB and here is the message:
 Program received signal SIGILL, Illegal instruction.
 0x00005555555e40b0 in
 _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs
 ()


[...]

There are a few possible causes:

1) There's a pointer bug in your program that corrupted some memory,
causing a function pointer to point to something that isn't a function,
and when the CPU tried to execute instructions from there it triggered a
fault.

2) The optimized assembly code in std.bigint may contain an instruction
that's incompatible with your CPU, so a fault is triggered when the CPU
tried to execute it.

3) Your program may have been incorrectly linked, and the ABI
incompatibility could have triggered this fault.

4) You may be using std.bigint for numbers far bigger than the range
it's designed for.  While this is unlikely to be the cause of this error
(I've tested std.bigint with numbers up to 100,000+ digits without any
crashes), using an unusually large number may cause the code to do
something unexpected that may trigger the crash.  The chances are pretty
low that this is actually the case, though.


Among the above causes, I'd say (1) is the most likely, (2) is the 2nd
most likely if (1) isn't the cause.


T

-- 
Truth, Sir, is a cow which will give [skeptics] no more milk, and so they are
gone to milk the bull. -- Sam. Johnson
Jun 18
parent Murilo <murilomiranda92 hotmail.com> writes:
On Wednesday, 19 June 2024 at 00:02:38 UTC, H. S. Teoh wrote:


 Among the above causes, I'd say (1) is the most likely, (2) is 
 the 2nd
 most likely if (1) isn't the cause.


Thank you, I will try this software on other computers to see if 
it's number 2. I've reviewed the code and I don't think it could 
be number 1.
Jun 19
prev sibling next sibling parent reply ryuukk_ <ryuukk.dev gmail.com> writes:
On Tuesday, 18 June 2024 at 23:07:47 UTC, Murilo wrote:

 I've created a software which performs the Fermat's Primality 
 Test, however if I input a very big number it causes an error 
 saying "Illegal instruction (core dumped)". Does anyone know 
 why?

 I've used GDB and here is the message:
 Program received signal SIGILL, Illegal instruction.
 0x00005555555e40b0 in 
 _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()

 Here is the link to the source code: 
 https://github.com/MuriloMir/Fermat-primality-test




```D
else if (BigInt(to!string(tester)) ^^ number % number != tester)
```

why do you convert the number to string?
Jun 19
parent Murilo <murilomiranda92 hotmail.com> writes:
On Wednesday, 19 June 2024 at 07:46:07 UTC, ryuukk_ wrote:


 why do you convert the number to string?


My mistake, I thought BigInt() only took strings, I've corrected 
the code.
Jun 19
prev sibling next sibling parent Basile B. <b2.temp gmx.com> writes:
On Tuesday, 18 June 2024 at 23:07:47 UTC, Murilo wrote:

 I've created a software which performs the Fermat's Primality 
 Test, however if I input a very big number it causes an error 
 saying "Illegal instruction (core dumped)". Does anyone know 
 why?

 I've used GDB and here is the message:
 Program received signal SIGILL, Illegal instruction.
 0x00005555555e40b0 in 
 _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()

 Here is the link to the source code: 
 https://github.com/MuriloMir/Fermat-primality-test


That has to be an assertion failure happening at runtime. IIRC 
the `ud2` instruction (causing SIGILL) is used in -betterC mode. 
If you look at biguintcore.d you'll see a couple of them, e.g 
https://github.com/dlang/phobos/blob/master/std/internal/math/biguintcore.d#L1042.
Jun 20
prev sibling next sibling parent Timon Gehr <timon.gehr gmx.ch> writes:
On 6/19/24 01:07, Murilo wrote:

 I've created a software which performs the Fermat's Primality Test, 
 however if I input a very big number it causes an error saying "Illegal 
 instruction (core dumped)". Does anyone know why?
 
 I've used GDB and here is the message:
 Program received signal SIGILL, Illegal instruction.
 0x00005555555e40b0 in 
 _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()
 
 Here is the link to the source code: 
 https://github.com/MuriloMir/Fermat-primality-test


Looking at the code, this is probably the cause:

```
if (BigInt(tester) ^^ number % number != tester)
```

This uses roughly as much memory as `number` is big, times the `log` of 
`tester`. You'd have to implement your own modular exponentiation that 
does not compute the full intermediate result, the you use only roughly 
`log` of `number` memory.
Jun 26
prev sibling parent Sergey <kornburn yandex.ru> writes:
On Tuesday, 18 June 2024 at 23:07:47 UTC, Murilo wrote:

 I've created a software which performs the Fermat's Primality 
 Test, however if I input a very big number it causes an error 
 saying "Illegal instruction (core dumped)". Does anyone know 
 why?

 I've used GDB and here is the message:
 Program received signal SIGILL, Illegal instruction.
 0x00005555555e40b0 in 
 _D3std8internal4math11biguintcore7BigUint3powFNaNbNfNkMSQCcQCbQBvQBtQBjmZQs ()

 Here is the link to the source code: 
 https://github.com/MuriloMir/Fermat-primality-test


Another point.. never use std.bigint for something serious.
At first you can try to use https://code.dlang.org/packages/gmp-d 
and see if the problem is still presented
Jun 26