heavy_hex generator functions raises PanicException if you pass d=1

[mtreinish]

Information

• retworkx version: 0.10.2
• Python version: 3.9
• Rust version: 1.54
• Operating system: Linux

What is the current behavior?

When passed d=1 to retworkx.generators.heavy_hex_graph or retworkx.generators.directed_heavy_hex_graph it raises a PanicException (meaning there was a panic in rust):

thread '<unnamed>' panicked at 'assertion failed: `(left != right)`
  left: `0`,
 right: `0`', /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/slice/mod.rs:790:9
stack backtrace:
   0:     0x7fbfa4f0d815 - std::backtrace_rs::backtrace::libunwind::trace::h34055254b57d8e79
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/../../backtrace/src/backtrace/libunwind.rs:90:5
   1:     0x7fbfa4f0d815 - std::backtrace_rs::backtrace::trace_unsynchronized::h8f1e3fbd9afff6ec
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fbfa4f0d815 - std::sys_common::backtrace::_print_fmt::h3a99a796b770c360
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x7fbfa4f0d815 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h32d1f94a80615d18
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:46:22
   4:     0x7fbfa4ee88ec - core::fmt::write::h306731c068f7162c
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/fmt/mod.rs:1110:17
   5:     0x7fbfa4f0b9e4 - std::io::Write::write_fmt::hd2fa90334eee2a21
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/io/mod.rs:1588:15
   6:     0x7fbfa4f0c9eb - std::sys_common::backtrace::_print::h5abaa2601a852287
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:49:5
   7:     0x7fbfa4f0c9eb - std::sys_common::backtrace::print::h8d81445442bb638f
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:36:9
   8:     0x7fbfa4f0c9eb - std::panicking::default_hook::{{closure}}::hcfe804496a9fa747
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:208:50
   9:     0x7fbfa4f0b5e1 - std::panicking::default_hook::hbea8e3ccf2ba8901
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:225:9
  10:     0x7fbfa4f0b5e1 - std::panicking::rust_panic_with_hook::h7ee9e1a2d0f8975a
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:622:17
  11:     0x7fbfa4f256f8 - std::panicking::begin_panic_handler::{{closure}}::h8ab3b4491718b2c7
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:519:13
  12:     0x7fbfa4f2566c - std::sys_common::backtrace::__rust_end_short_backtrace::hd489062ffa586a9f
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/sys_common/backtrace.rs:141:18
  13:     0x7fbfa4f2561d - rust_begin_unwind
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/std/src/panicking.rs:515:5
  14:     0x7fbfa4d471e0 - core::panicking::panic_fmt::hca6330e3e14086b4
                               at /rustc/a178d0322ce20e33eac124758e837cbd80a6f633/library/core/src/panicking.rs:92:14
  15:     0x7fbfa4ee8dcb - core::panicking::assert_failed_inner::h33b45280069a80ed
  16:     0x7fbfa4d3ba6a - core::panicking::assert_failed::h4b7cf0bc1bcfbd1c
  17:     0x7fbfa4e4057f - retworkx::generators::__pyo3_raw_heavy_hex_graph::h72150d4404ab93c2
  18:     0x7fbfa5d8233b - <unknown>
  19:     0x7fbfa5d7f107 - _PyEval_EvalFrameDefault
  20:     0x7fbfa5d79489 - <unknown>
  21:     0x7fbfa5d78e71 - _PyEval_EvalCodeWithName
  22:     0x7fbfa5e30b13 - PyEval_EvalCode
  23:     0x7fbfa5e40884 - <unknown>
  24:     0x7fbfa5e3c55b - <unknown>
  25:     0x7fbfa5d5d2b9 - <unknown>
  26:     0x7fbfa5d5d46f - PyRun_InteractiveLoopFlags
  27:     0x7fbfa5cea3a3 - PyRun_AnyFileExFlags
  28:     0x7fbfa5cdefe7 - <unknown>
  29:     0x7fbfa5e230a9 - Py_BytesMain
  30:     0x7fbfa5aadb25 - __libc_start_main
  31:     0x560a350db04e - _start
  32:                0x0 - <unknown>
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
pyo3_runtime.PanicException: assertion failed: `(left != right)`
  left: `0`,
 right: `0`

with RUST_BACKTRACE=full set

What is the expected behavior?

The function either works, or raises an exception on why 1 is an invalid value for d.

Steps to reproduce the problem

import retworkx
retworkx.generators.heavy_hex_graph(1)

[georgios-ts]

The source of the problem is this line L1536 since chunks panics if chunk size is 0 (see https://doc.rust-lang.org/std/primitive.slice.html#panics-2). Giving as input d=1 the output graph will be just a single node which is not really meaningful but i don't see also any reason to raise an exception.

[mtreinish]

Yeah, I agree there's no reason to error, I think we should just add a short circuit return of a single node graph if d == 1.