For a project I needed both / 10 and %10 several times. Although the straightforward code was fast enough I investigated if it could be even faster. Could be useful e.g. for a library or so. This resulted in the following divmod10() function that calculates both the divide by 10 and the modulo 10 "s…

I am using a very new version of SdFat, not the 3-4 year old version in SD.h. I have some extra stuff in my loop to time the max and min print time but commenting it out doesn't change much. The new SdFat is much faster, it allows flash programming to happen in the SD while the next block buffer i…

Paul, I tried your sketch on a Uno with 1.0.5 and get a fast write with SD.h and the new Print. About the same as with the new SdFat. Looks like you don't even need the SdFat improvements at 50 KB/sec. Initializing SD card...card initialized. seconds = 2.53

There is another speed optimization to make when you are using divmod10 to convert a long into base-10 digits: Only the first few digits of a 10-digit number need full 32-bit precision. Once the high byte is 0 you only need 24 bit precision (saves at least 10 cycles), then when the two highest bytes…

a well implemented trick - trading space for speed - There are other tricks possible, not investigated though Consider the fact that the largest uint32_t < 50000 * 10000 * 10000; with a divmod10000() one could divide the uint32 in 4digit chunks which can be processed by divmod10_asm16 a divmod10…

I have used the ideas here to improve the speed of logging data to SD cards. I wrote functions to print a numerical field to an SD card that are as much as five times faster than the standard Arduino print. I am now able to log data from four analog pins on an Uno to an SD at 2000 Hz. This is 8000 …

robtillaart: think divmod10() should become part of the core seeing these and the above numbers. I'm planning to release it in the next version of Teensyduino. Stimmer, is Arduino Print LGPL ok with you? Would you like your name to appear, other than "Stimmer" and link to this forum topic? You …

Credit is not enough. Open source licenses require a copyright claim by Stimmer.

Ok then. I'll hold off publishing anything until Stimmer replies. I'm currently working on a Mac-related USB problem, so it's not like there's any hurry. But it would be nice to publish this code to a wider audience, if that's allowed?

@Paul :wink: Shouldn't you be working on a space related issue with the Teensy uploader ]:smiley: Best regards Jantje

divmod10() : a fast replacement for /10 and %10 (unsigned)

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robtillaart July 8, 2013, 7:47pm 90

Impressive numbers, really good !

think divmod10() should become part of the core seeing these and the above numbers.

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divmod10() : a fast replacement for /10 and %10 (unsigned)

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