generate half precision table

gistfile1.c

#include <stdio.h>
#include <stdint.h>

uint32_t basetable[512];
uint32_t shifttable[512];

void generatetables(){
	unsigned int i;
	int e;
	for(i=0; i<256; ++i){
		e=i-127;
		if(e<-24){ // Very small numbers map to zero
			basetable[i|0x000]=0x0000;
			basetable[i|0x100]=0x8000;
			shifttable[i|0x000]=24;
			shifttable[i|0x100]=24;
		}
		else if(e<-14){ // Small numbers map to denorms
			basetable[i|0x000]=(0x0400>>(-e-14));
			basetable[i|0x100]=(0x0400>>(-e-14)) | 0x8000;
			shifttable[i|0x000]=-e-1;
			shifttable[i|0x100]=-e-1;
		}
		else if(e<=15){ // Normal numbers just lose precision
			basetable[i|0x000]=((e+15)<<10);
			basetable[i|0x100]=((e+15)<<10) | 0x8000;
			shifttable[i|0x000]=13;
			shifttable[i|0x100]=13;
		}
		else if(e<128){ // Large numbers map to Infinity
			basetable[i|0x000]=0x7C00;
			basetable[i|0x100]=0xFC00;
			shifttable[i|0x000]=24;
			shifttable[i|0x100]=24;
		}
		else{ // Infinity and NaN's stay Infinity and NaN's
			basetable[i|0x000]=0x7C00;
			basetable[i|0x100]=0xFC00;
			shifttable[i|0x000]=13;
			shifttable[i|0x100]=13;
		}
	}
}

unsigned int convertmantissa(unsigned int i){
	unsigned int m=i<<13;
 unsigned int e=0;
 // Zero exponent
 while(!(m&0x00800000)){
 // While not normalized
 e-=0x00800000;
 // Decrement exponent (1<<23)
 m<<=1;
 // Shift mantissa
 }
 m&=~0x00800000;
 // Clear leading 1 bit
 e+=
 0x38800000;
 // Adjust bias ((127-14)<<23)
 return m | e;
 // Return combined number
}

int main(void)
{
	uint32_t mantissatable[2048];
	mantissatable[0] = 0;
	int i, j;
	for (i = 1; i < 1024; i++)
		mantissatable[i] = convertmantissa(i);
	for (i = 1024; i < 2048; i++)
		mantissatable[i] = 0x38000000 + ((i-1024)<<13);
	/*
	for (i = 0; i < 256; i++)
	{
		for (j = 0; j < 7; j++)
			printf("0x%x, ", mantissatable[i * 8 + j]);
		printf("0x%x,\n", mantissatable[i * 8 + 7]);
	}
	*/
	generatetables();
	/*
	for (i = 0; i < 32; i++)
	{
		for (j = 0; j < 15; j++)
			printf("0x%x, ", basetable[i * 16 + j]);
		printf("0x%x,\n", basetable[i * 16 + 15]);
	}
	*/
	uint32_t exponenttable[64];
	exponenttable[0] = 0;
	exponenttable[32]= 0x80000000;
	for (i = 1; i < 31; i++)
		exponenttable[i] = i<<23;
	for (i = 33; i < 63; i++)
		exponenttable[i] = 0x80000000 + ((i-32)<<23);
	exponenttable[31]= 0x47800000;
	exponenttable[63]= 0xC7800000;
	for (i = 0; i < 8; i++)
	{
		for (j = 0; j < 7; j++)
			printf("0x%x, ", exponenttable[i * 8 + j]);
		printf("0x%x,\n", exponenttable[i * 8 + 7]);
	}
	uint32_t offsettable[64];
	for (i = 0; i < 64; i++)
		offsettable[i] = 1024;
	offsettable[0] = 0;
	offsettable[32]= 0;
	/*
	for (i = 0; i < 8; i++)
	{
		for (j = 0; j < 7; j++)
			printf("0x%x, ", offsettable[i * 8 + j]);
		printf("0x%x,\n", offsettable[i * 8 + 7]);
	}
	*/
	return 0;
}