Namaste. This is wrt the TOMS748 math root finding implementation: Given that `if(fa == 0)` is handled at: https://github.com/boostorg/math/blob/develop/include/boost/math/tools/toms7... … and the function returns in case of the above condition, it is not clear to me what the need is for the `if (fa != 0)` at: https://github.com/boostorg/math/blob/develop/include/boost/math/tools/toms7... Note that I do not find the condition being applied at the SciPy implementation of this algorithm at: https://github.com/scipy/scipy/blob/v1.6.0/scipy/optimize/zeros.py#L1220 Now I also note similar checks at: https://github.com/boostorg/math/blob/develop/include/boost/math/tools/toms7... https://github.com/boostorg/math/blob/develop/include/boost/math/tools/toms7... … but regarding those lines, while I can understand the need for checking there after more bracketing work is done, it is not clear to me why `(fa == 0)` is alone checked for, and not `(fb == 0)` as well. I would have thought the algorithm is not biased towards a or b. Indeed, in the last steps from: https://github.com/boostorg/math/blob/develop/include/boost/math/tools/toms7..., … both the conditions are checked for, which is what I would expect even in the intervening steps. Now the lines seem to have originated in the very first commit implementing this algorithm: https://github.com/boostorg/math/commit/79a8199f9c26ba353fb52ec4543f75ffc2a8... … but I do not see a way to contact the author jzmaddock other than posting to this list, so I hope someone/they see here and reply. Thanks! -- Shriramana Sharma ஶ்ரீரமணஶர்மா श्रीरमणशर्मा 𑀰𑁆𑀭𑀻𑀭𑀫𑀡𑀰𑀭𑁆𑀫𑀸