![FortranTip on Twitter: "Use d0 or _kind to make a constant double precision. Merely having many decimal places in a literal constant does not do so. real(kind(1.0d0)) :: pi pi = 3.14159265358979323846 ! FortranTip on Twitter: "Use d0 or _kind to make a constant double precision. Merely having many decimal places in a literal constant does not do so. real(kind(1.0d0)) :: pi pi = 3.14159265358979323846 !](https://pbs.twimg.com/media/FIVxkpnVIAAKD7U.jpg:large)
FortranTip on Twitter: "Use d0 or _kind to make a constant double precision. Merely having many decimal places in a literal constant does not do so. real(kind(1.0d0)) :: pi pi = 3.14159265358979323846 !
![Table 5 from Why .1 + .1 Might Not Equal .2 and Other Pitfalls of Floating-Point Arithmetic | Semantic Scholar Table 5 from Why .1 + .1 Might Not Equal .2 and Other Pitfalls of Floating-Point Arithmetic | Semantic Scholar](https://d3i71xaburhd42.cloudfront.net/0923a86428acad420dc3e8dadb6e6ec7203eeee8/18-Table11-1.png)
Table 5 from Why .1 + .1 Might Not Equal .2 and Other Pitfalls of Floating-Point Arithmetic | Semantic Scholar
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800 Pieces Cotton Swabs, Double Precision Tips with Paper Stick, 4 Packs, 200 Pi 705353083822 | eBay
![Fractional error of Riemann-Zeta function calculation of pi using 2nd order Richardson Extrapolation | scatter Fractional error of Riemann-Zeta function calculation of pi using 2nd order Richardson Extrapolation | scatter](https://plotly.com/~BlakeRaymond/23/fractional-error-of-riemann-zeta-function-calculation-of-pi-using-2nd-order-rich.png)