Marc Jornet Sanz (Interview)

Marc Jornet Sanz first competed in the Mental Calculation World Cup in 2010, winning the overall silver medal. In 2018 he is stronger than ever, winning gold for calendar calculations, silver for multiplications, and 3rd place for the standard tasks. We interviewed him at the 2018 World Cup soon after he set a massive new record for 8-by-8 multiplications with 10 problems correctly solved in just 2 minutes 49.85 seconds.

Congratulations on breaking the multiplication world record for the 4th time this weekend! It’s the first time that anyone has officially gone beneath 3 minutes. Have you gone any faster during training?

In training, my best time with all multiplications correctly solved was 2 minutes 54 seconds, so it’s curious that I got my best score of 2:49 precisely at the world record attempt! Nonetheless, I was quite comfortable solving all ten multiplications in under 3 minutes in training, although it’s very difficult to get all multiplications correct. For one single multiplication, my best time is 9 seconds, and I’ve done less than 13 seconds lots of times.

What’s going on in your mind when you’re calculating these multiplications? Are you using the soroban/abacus or do you process the numbers in a different way?

I use the cross method from right to left, one digit each time, with no soroban. I don’t verbalize nor say the numbers in my head. The numbers just pass through my brain unconsciously, as if I knew the results by heart. In fact, in training, I usually watch TV or think about other things while I do the multiplications.

What affects your performance in calculation in general – does your speed or accuracy fluctuate?

It depends on the day. Some days I solve all multiplications correctly, and some other days I make lots of mistakes. However, certainly I’m much more rapid in the evening and night than in the morning (it’s a pity that the World Cup is in the morning!) I’m a person that finds it difficult to wake up in the morning, so I need time to be bright. That’s why my world record was done at 9:30 pm!

You and Jeonghee Lee each set new multiplication records in a busy restaurant one evening. Do the distractions not affect you?

For multiplications (and mental calendar dates), noise is not a problem for me. I don’t verbalize numbers, I don’t think of them, just the results come out. In fact, I know that I’m ready for the competition and world record attempts when distractions do not affect me, because that means that I’m calculating unconsciously.

In square roots, for example, distractions affect me more, because I’ve not trained roots as much as multiplications, so sometimes I verbalize the numbers to myself, and this must not be done! I believe that a good calculator has to visualize numbers and compute unconsciously, not verbalize.

How has the competition changed since you first competed?

Before 2010 there were just 2 surprise tasks. In 2010 there were 6 surprise tasks, although with a total score of only 100 points. Since 2012, there are 5 surprise tasks plus a challenge task, which score 600 points in total. So to compete against people like Wenzel Grüß – who are very strong in the surprises – you have to prepare more for these tasks. The scoring system this year also penalizes mistakes very severely.

Also, in 2010 the competitors were mainly from Europe, but now there are people from all over the world, especially Asia and countries where mental calculation is regarded as important. The competition is tougher because there are now competitors who have been training seriously since they were children. For me, it’s a challenge to compete because I also have to work on my PhD.

What PhD are you doing?

It’s in Stochastics – specifically Random Differential Equations – at Universitat Politècnica de València. I studied a Mathematics degree at Universitat de València, and two masters in Barcelona. Since I was a child, I enjoyed pure Mathematics. I love the theory and proofs of theorems.

Many calculators are not experienced in Mathematics but are nonetheless very skilful – do you find much link between Mathematics and mental calculation?

For me, mental calculation is an excellent complement for a mathematician. The patterns, properties and laws of numbers and magnitudes; topics in elementary number theory such as modulo calculation, the field Z/p, the Chinese remainder theorem, etc.; manipulation of algebraic equations; numerical methods such as Newton-Raphson or bisection methods; or elementary functions such as the logarithm – these get a new insight and meaning when you discover how useful they can be for mental calculation. In fact, mental calculation is a branch of Mathematics similar to numerical calculus: numerical methods look for the best algorithms for a computer, while mental calculation seeks the best algorithms for human brain.

How do you prepare for these competitions?

I started in the world of mental calculation when I was 14 years old, by watching videos on YouTube. By reading on the Internet and in books, I found out the best techniques for my capabilities. I remember that the mental calculator Freddis Reyes helped me a lot by email (he showed me his technique for mental calendar dates, he talked to me about the organizer Ralf Laue, etc.), and I’m very grateful to him. In 2010 (16 years old), I participated in my first World Cup and I won at multiplications. At that moment, my problem was that I knew very few techniques. For square roots, I used the method taught in primary school, in which at each step numbers become bigger and bigger! In 2014, I participated again in the World Cup, and it was the first time I won calendar dates and did relatively well in square roots. Now that I’m 24 and it’s been my third World Cup, I’ve optimized the techniques I use for multiplication, roots, division and calendar dates, although every method is improvable.

I’d like to have more time to practise mental calculation and someone to train me. During my daily life, I give up mental calculation because of my career at university. If I’m able to attend the competition, I usually start training four of five months before it, one hour of training per day. This year I wasn’t going to participate, but the last week of May I decided to do so, and I set a new world record!

I practise multiplications and calendar dates a lot. I also like long divisions and to compute deep roots with logarithms and antilogarithms, but in this World Cup 2018 no surprise task was related to roots 🙁 In general, one should prepare surprise tasks as much as standard tasks. And the most important, have fun with numbers and meet great and friendly people from all over the world with incredible skills and the same interests.

Best of luck for your PhD Marc, and maybe we’ll meet again in 2020 for Memoriad in Dubai, or the next World Cup. If you would like to contact Marc directly, he receives email at marjorsa@doctor.upv.es