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70 lines
1.7 KiB
Markdown
70 lines
1.7 KiB
Markdown
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[← Home](../README.md) · [Libraries](README.md)
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# Math Libraries — Floating Point
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## Overview
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AmigaOS provides multiple math libraries for floating-point operations. The 68000 has no FPU, so all math is done in software unless a 68881/68882/68040/68060 FPU is present.
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---
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## Library Stack
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| Library | Format | Description |
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|---|---|---|
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| `mathffp.library` | FFP (Motorola Fast Floating Point) | Original Amiga format (32-bit) |
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| `mathieeesingbas.library` | IEEE 754 single (32-bit) | IEEE single precision |
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| `mathieeedoubbas.library` | IEEE 754 double (64-bit) | IEEE double precision |
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| `mathtrans.library` | FFP | Transcendental functions (sin, cos, sqrt) |
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| `mathieeesingtrans.library` | IEEE single | IEEE single transcendentals |
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| `mathieeedoubtrans.library` | IEEE double | IEEE double transcendentals |
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---
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## FFP Format
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Motorola FFP is NOT IEEE 754:
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```
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Bits 31–8: 24-bit mantissa (normalised, implicit 1.xxx)
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Bits 7–1: 7-bit exponent (excess-64)
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Bit 0: sign (0=positive, 1=negative)
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```
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---
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## Using IEEE Math
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```c
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struct Library *MathIeeeSingBasBase =
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OpenLibrary("mathieeesingbas.library", 0);
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float a = 3.14f;
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float b = 2.0f;
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float c = IEEESPMul(a, b); /* 6.28 */
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float d = IEEESPAdd(a, b); /* 5.14 */
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float e = IEEESPDiv(a, b); /* 1.57 */
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CloseLibrary(MathIeeeSingBasBase);
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```
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---
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## 68881/68882 FPU
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When an FPU is present, the math libraries are replaced with ROM patches that use native FPU instructions. The application code is identical — the library transparently switches to hardware.
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```c
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if (SysBase->AttnFlags & AFF_68881) {
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/* 68881/68882 FPU present */
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}
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if (SysBase->AttnFlags & AFF_FPU40) {
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/* 68040 internal FPU */
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}
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```
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---
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## References
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- NDK39: `libraries/mathffp.h`, `libraries/mathieeesp.h`
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