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Prevent underflow in floating point division in Python

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问题 Suppose both x and y are very small numbers, but I know that the true value of x / y is reasonable. What is the best way to compute x/y ? In particular, I have been doing np.exp(np.log(x) - np.log(y) instead, but I'm not sure if that would make a difference at all? 回答1: Python uses the floating-point features of the hardware it runs on, according to Python documentation. On most common machines today, that is IEEE-754 arithmetic or something near it. That Python documentation is not explicit

Underflow in Forward Algorithm for HMMs

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问题 I'm implementing the forward algorithm for HMMs to calculate the probability of a given HMM emitting a given observation sequence. I'd like my algorithm to be robust to underflow. I can't work in log-space because the forward algorithm requires the multiplication AND addition of probabilities. What is the best way to avoid underflow? I've read some sources about this but the best suggestion I get is scaling the probabilities at each time step Section 6 Here. By the end of the algorithm you

Underflow in Forward Algorithm for HMMs

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When does underflow occur?

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问题 I get into a situation where calculating 1.77e-308/10 triggers an underflow exception, but calculating 1.777e-308/10 does not. This is strange because: Underflow occurs when the true result of a floating point operation is smaller in magnitude (that is, closer to zero) than the smallest value representable as a normal floating point number in the target datatype (from Arithmetic Underflow, Wikipedia) In other words, if we calculate x/y where both x and y are double , then underflow should

Buffer underrun and ResourceExhausted errors with tensorflow

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问题 I'm in high school and I'm trying to do a project involving neural networks. I am using Ubuntu and trying to do reinforcement learning with tensorflow, but I consistently get lots of underrun warnings when I train a neural network. They take the form of ALSA lib pcm.c:7963:(snd_pcm_recover) underrun occurred . This message is printed to the screen more and more frequently as training progresses. Eventually, I get a ResourceExhaustedError and the program terminates. Here is the full error

Causing underflow in ieee-754 floating point format using subtraction

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问题 This seems basic but I am having a lot of trouble answering the following question: Give two numbers X and Y represented in the IEEE754 format such that computing X-Y will result in underflow. To my understanding every operation can potentially result in underflow but for the life of mine I cant find an example for subtraction. PLEASE HELP!!! thanks 回答1: When default exception handling is in effect, a subtraction that produces a tiny (in the subnormal interval 1 ) non-zero result conceptually

How can I prevent/detect an underflow in a Postgresql calculation that uses EXP()

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问题 I am receiving a value out of range: underflow error from pgsql, in a query that uses the EXP(x) function. What values of x trigger this? How do I prevent or detect it? 回答1: The function exp is called the exponential function, and its inverse is the natural logarithm, or logarithm to base e. The number e is also commonly defined as the base of the natural logarithm In other words, exp(x) and e^x are the same function. However, since e is a transcendental number, and therefore irrational, its

Flush-to-zero in gfortran

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问题 Is there a way to force flush-to-zero of underflows in gfortran? I can't believe this is the first time someone has asked this, but I couldn't find anything on it anywhere. Mea culpa if this is a duplicate. 回答1: You can accomplish this with recent versions of gfortran that support the Fortran 2003 IEEE modules. The standard defines two underflow modes -- gradual and abrupt. Abrupt is the one you want which sets underflow to 0 and signals the underflow floating point exception. You can test

Flush to Zero when a computation results in a denormal number in linux

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A computation in my C code is producing a gradual underflow, and when it happens the program is terminating with SIGFPE. How can I flush the result to zero when a gradual underflow (Denormal) results from a computation, and not terminate the execution? (I am working on a redhat linux machine). Thanks. You haven't specified the architecture - I'm going to take a guess that it's a relatively recent x86[-64], in which case you can manipulate the SSE control register using _mm_getcsr , _mm_setcsr , specified in the <xmmintrin.h> (or <immintrin.h> ) header. The 'flush-to-zero' bit is set with

Flush to Zero when a computation results in a denormal number in linux

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问题 A computation in my C code is producing a gradual underflow, and when it happens the program is terminating with SIGFPE. How can I flush the result to zero when a gradual underflow (Denormal) results from a computation, and not terminate the execution? (I am working on a redhat linux machine). Thanks. 回答1: You haven't specified the architecture - I'm going to take a guess that it's a relatively recent x86[-64], in which case you can manipulate the SSE control register using _mm_getcsr , _mm