Implementing Sparse Vectors With Associative Arrays/Compiler Bug?

[Rene Zwanenburg]

On Thursday, 7 March 2013 at 09:43:21 UTC, jerro wrote:
>> Are errors of this magnitude to be expected using doubles, or 
>> is this a compiler bug?
>
> Errors of this magnitude are to be expected. the value of accum 
> in your example is somewhere around 3e+08, so the relative 
> error is around 1e-15, and double.epsilon is 2.22045e-16.

This.

You can use reals to store the intermediary results. A real has 
the largest hardware supported size, which is 80 bits for x87. 
It's not a silver bullet but can be useful in cases like this.