Compilling with float?

[markusmueller19]

Posted on May 28, 2009 at 13:24

Compilling with float?

[sjo]

Posted on May 17, 2011 at 12:36

that quite old version of the arm gcc compiler.

i would check with a newer arm-eabi compiler, floating point performance is supposed to have improved quite a bit over the older arm-elf compiler. Cheers sjo

[16-32micros]

Posted on May 17, 2011 at 12:36

Hi sjo, Asterix,

I've done some basic measurements with RVCT ( Keil 3.22) and EWARM 5.11 from IAR using our Cortex-M3 and here is my function : #include #define __pi 3.14159265 float var1 = __pi ; float var2 = __pi/2; float var0[10] = {0,0,0,0,0,0,0,0,0,0}; int main(void) { var0[0]= cos(var1); var0[1]= sin(var1); var0[2]= sqrt(var1); var0[3]= atan(var1); var0[4]= var2 + var1; var0[5]= var2 * var1; var0[6]= var2 / var1; while(1); } Results are : Cortex-M3, Keil 3.22 compiler 32 bit floats,exact CPU cyclescos 41359 sin 43389 sqrt 3090 atan 42243 add 127 mul 624 div 445 Cortex-M3, IAR 5.11 compiler 32 bit floats,exact CPU cyclescos 1864 sin 1946 sqrt 2725 atan 3423 add 40 mul 33 div 53 I'm quite surprised too by the results, where I see that keil is completely off while using trigonometric libraries. May be I'm missing something here ? Could you please try the same at your end and tell me your results for GCC from codesourcery. Cheers, STOne-32.

[niklas]

Posted on May 17, 2011 at 12:36

Hi STOne-32

We just bought the Keil compiler and I got a bit worried about your results, even if floats are not that important to us. I used toolchain version 3.20 and tried with and without the ''MicroLIB''. The difference was huge. With MicroLIB: cos 34443 sin 36140 sqrt 2319 atan 35339 add 120 mult 525 div 327 Without MicroLIB: cos 2957 sin 3006 sqrt 821 atan 2800 add 56 mult 58 div 92 It seems the MicroLIB is not that good at floats. When asking about the drawbacks with using MicroLIB the answer has been ''None, its better''. Now we know at least one difference 🙂 /Niklas

[markusmueller19]

Posted on May 17, 2011 at 12:36

How can I measure the count of Instructions? Is there a Register where I can read?

[16-32micros]

Posted on May 17, 2011 at 12:36

Hi Niklas,

Thank you a lot for the hint !! You are right and Here I have re-checked again my results and I get new ones : Results are : Cortex-M3, Keil 3.22 , Option -03 Time + ''Use MicroLib Checked'',exact CPU cycles cos 29097 sin 30516 sqrt 2028 atan 29795 add 87 mul 449 div 249 Cortex-M3, Keil 3.22 , Option -03 Time + ''Use MicroLib NOT Checked'',exact CPU cycles cos 2667 sin 2710 sqrt 728 atan 2587 add 35 mul 38 div 68 => However, I see that Program code size is now muliplied by x2 from 6K to 12K which is quite reasonable. Cortex-M3, IAR 5.11 compiler 32 bit floats,exact CPU cycles cos 1864 sin 1946 sqrt 2725 atan 3423 add 40 mul 33 div 53 So Now I see that IAR and Keil are quite similar in average 😉 Hi markus, In my program I simply used Systick Counter and removing some software overhead for funtion entries and then stores results in a Results[] Table. /* Configure HCLK/CPU clock as SysTick clock source */ SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK); SysTick_SetReload(0xFFFFFF); /* Enable the SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Enable); var0[0] = var1; SysTick_CounterCmd(SysTick_Counter_Disable); Dummytiming= 0xFFFFFF - SysTick_GetCounter(); /* Clear the SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Clear); SysTick_SetReload(0xFFFFFF); /* Enable the SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Enable); var0[0]=cos(var1); SysTick_CounterCmd(SysTick_Counter_Disable); Results[0]= 0xFFFFFF - SysTick_GetCounter() - Dummytiming; /* Clear the SysTick Counter */ SysTick_CounterCmd(SysTick_Counter_Clear); ..... Cheers, STOne-32. [ This message was edited by: STOne-32 on 11-06-2008 20:33 ]

[niklas]

Posted on May 17, 2011 at 12:36

Hi Markus

Hi STOne-32 I measured the execution time by running each of the functions in the debugger and checking the CYCCNT register before and afterwards. In Keil uVision this is shown in the Regs tab under Internal, but it can be access at address 0xE0001004 (according to the Cortex-M3 ref. man.). I read a bit about the MicroLIB in Keil's Online manual and it states As MicroLib has been optimized to minimize code size, some functions will execute more slowly than the standard C library routines available in the RealView compilation tools.It also states Microlib can sensibly be used with either --fpmode=std or --fpmode=fast.I tried using --fpmode=fast but I did not notice any difference, but perhaps you need to define the variables as double instead of float to notice. /Niklas

[markusmueller19]

Posted on May 17, 2011 at 12:36

Hello,

Read from Address 0xE0001004 is always 0: #define CORE_SysTick (*((u32*)0xE0001004)) int Systiming = CORE_SysTick; If I want use cos() then the cpu go to interrupt HardFaultException() Line: var0[0]=cos(var1); The compiller have no errors and warnings, I have all libs included: arm-none-eabi-ld -v -e 0 -LC:/WinARM/CodeSourcery/lib/gcc/arm-none-eabi/4.2.3/thumb -LC:/WinARM/CodeSourcery/arm-none-eabi/lib/thumb -Tprj/STM32F103CB-ROM.ld -Map=main.map out/src/main.o out/src/stm32f10x_it.o out/src/stm32f10x_vector.o -lm -lgcc --output main.elf What make I wrong?

[sjo]

Posted on May 17, 2011 at 12:36

you need to enable the counter, eg.

0xE0001000 = 0x40000001; /* set bit0 */ Cheers sjo

[suyongyao]

Posted on May 17, 2011 at 12:36

Hi STOne-32

I'm trying to do floating point operations on STM32 too. I tried to run the code on my IAR KickStart board via IAR JLINK but the results of array var0[] were unavailable. Can I have ur IAR project of this? Thank you. [ This message was edited by: suyongyao on 13-06-2008 11:17 ]

[markusmueller19]

Posted on May 17, 2011 at 12:36

Now, the SysTick Counter is working.

But I have problems with working with floats: volatile float Var1, Var2, Var3; Var2 = Var3 = 3.0; Var1 = Var2 + Var3; On this last Line comes a Exception and the core is going to the interrupt HardFaultException(). In Assembler: 0x0000043a : ldr r0, [sp, #8] 0x0000043c : ldr r1, [sp, #4] 0x0000043e : blx 0x8848 0x00000442 : str r0, [sp, #12] 0x00000444 : mov.w r5, #0 ; 0x0 0x00000448 : mov r7, r5 0x0000044a : mov r6, r5 I have no idea, what is wrong. Can you help me, please?